Stepper Motors are a digital device. Digital information is processed by the Stepper Motors to accomplish an end result, in this case, controlled motion. One may assume that Stepper Motors will dependably follow digital instructions just as a computer is expected to. This is the distinguishing feature for Stepper motors.

Stepper Motors are an electrical motor that is driven by digital pulses rather than a continuously applied voltage. Inherent in this concept is open-loop control, wherein a train of pulses translates into so many shaft revolutions, with each revolution requiring a given number of pulses. Each pulse equals one rotary increment, or step (hence, Stepper motors), which is only a portion of one complete rotation.

Therefore, counting pulses can be applied in Stepper Motors to achieve a desired amount of shaft rotation. The count automatically represents how much movement has been achieved, without the need for feedback information, as would be the case in servo systems.

Although Stepper Motors have been overshadowed in the past by servo systems for motion control, it now is emerging as the preferred technology in more and more areas. The major factor in this trend towards Stepper Motors is the prevalence of digital control, and the emergence of the microprocessor.

Today we have many Stepper Motors applications all around us. Stepper Motors are used in printers (paper feed, print wheel), disk drives, photo-typesetting, X-Y plotters, clocks and watches, factory automation, aircraft controls, and many other applications. The ingenuity and further advances in digital technology from researchers will continue to extend the list of applications in which Stepper Motors will be used.

There are three basic types of Stepper Motors. The Stepper Motors types vary by construction and in how they function. Each of these types of Stepper Motors offers a solution to an application in a different way. The three basic types of Stepper Motors include the Variable Reluctance, Permanent Magnet, and Hybrid.

Variable Reluctance (VR) Stepper Motors
Variable Reluctance Stepper Motors are known for having soft iron multiple rotor and a wound stator. The Variable Reluctance Stepper Motors generally operate in step angles from 5 to 15 degrees at relatively high step rates. They also possess no detent torque. In Figure 5, when phase A is energized, four rotor teeth line up with the four stator teeth of phase A by magnetic attraction. The next step is taken when A is turned off and phase B is energized, rotating the rotor clockwise 15 degrees; Continuing the sequence, C is turned on next and then A again. Counter clockwise rotation is achieved when the phase order is reversed.

Permanent Magnet (PM) Stepper Motors
Permanent Magnet Stepper Motors differ from Variable Reluctance Stepper Motors by having permanent magnet rotors with no teeth. These rotors are magnetized perpendicular to the axis. When the four phases are energized in sequence, the rotor rotates as it is attracted to the magnetic poles. The motor shown in Figure 6 will take 90 degree steps as the windings are energized in sequence ABCD. Permanent Magnet Stepper Motors generally have step angles of 45 to 90 degrees and tend to step at relatively low rates, but produce high torque and excellent damping characteristics.

Hybrid Stepper Motors
Hybrid Stepper Motors combine qualities from the permanent magnet and variable reluctance Stepper Motors. The Hybrid Stepper Motors have some of the desirable features of each. These Stepper Motors have a high detent torque, excellent holding and dynamic torque, and they can operate in high Stepper speeds. Step angles of 0.9 to 5.0 degrees are normally seen in Hybrid Stepper Motors. Bi-filar windings are generally supplied to these Stepper Motors so a single power supply can be used to power the Stepper Motors. The rotor will rotate in increments of 1.8 degrees if the phases are energized one at a time in the order they are indicated at. These Stepper Motors can be driven in two phases at a time to yield more torque. Hybrid Stepper Motors can also be driven by one then two then one phase to produce half steps of 0.9 degree increments.

There are three excitation modes that are commonly used with Stepper Motors. The Stepper Motors modes are the full-step, half-step- and micro-step.

Stepper Motors - Full-Step
In full step operation, Stepper Motors step through the normal step angle e.g. 200 step/revolution motors take 1.8 steps while in half step operation, 0.9 steps are taken. There are two kinds of full-step modes. Single phase full-step excitation is where Stepper Motors are operated with only one phase energized at-a-time. This mode should only be used where torque and speed performance are not important, e.g. where the motor is operated at a fixed speed and load conditions are well defined. Problems with resonance can prohibit operation at some speeds. This type of mode requires the least amount of power from the drive power supply of any of the excitation modes. Dual phase full-step excitation is where the Stepper Motors are operated with two phases energized at-a-time. This mode provides good torque and speed performance with a minimum of resonance problems. Dual excitation, provides about 30 to 40 percent more torque than single excitation, but does require twice the power from the drive power supply.

Stepper Motors - Half-Step
Stepper Motors have half-step excitation which is alternate single and dual phase operation resulting in steps one half the normal step size. This mode provides twice the resolution. While the motor torque output varies on alternate steps, this is more than offset by the need to step through only half the angle. This mode has become the predominately used mode by Anaheim Automation because it offers almost complete freedom from resonance problems. Stepper Motors can be operated over a wide range of speeds and used to drive almost any load commonly encountered.

Stepper Motors - Micro-Step
In Stepper Motors micro-step mode, a Stepper Motor's natural step angle can be divided into much smaller angles. For example, a standard 1.8 degree motor has 200 steps/revolution. If the motor is micro-stepped with a 'divide-by-10', then each micro-step would move the motor 0.18 degrees and there would be 2,000 steps/revolution. Typically, micro-step modes range from divide-by-10 to divide-by-256 (51,200 steps/rev for a 1.8 degree motor). The micro-steps are produced by proportioning the current in the two windings according to sine and cosine functions. This mode is only used where smoother motion or more resolution is required.

Stepper Motors are typically controlled by a driver and indexer. The amount, speed, and direction of rotation of Stepper Motors are determined by the right configuration of digital control devices. The main types of control devices for Stepper Motors are: Stepper Motors Drivers, Stepper Motors Control Links, and Stepper Motors Controllers. These devices are set up in figure 8. The Stepper Driver accepts the clock pulses and direction signals and translates these signals into appropriate phase currents for the Stepper Motor. The Stepper Indexer creates the clock pulses and the direction signals for the Stepper Motors. The computer or PLC (Programmable Logic Controller) sends out commands to the indexer.

Anaheim Automation offers a variety of options to customize Stepper Motors. The list of modifications includes, but is not limited to: shaft, brake, oil seal for an IP65 rating, mounting dimensions, speed, torque, and voltage. Please give Anaheim Automation a call for any custom applications using Stepper Motors.

Common Causes for Stepper Motors and/or Stepper Driver Failure
NOTE: Always read the specification sheet/user's guide that accompanies each product

Problem: Intermittent or erratic stepper motors or drivers function.
Solution: This is the most common cause of failure and one of the most difficult to detect. Start by checking to insure that all connections are tight between stepper motors and drivers. Evidence of discoloration at the terminals/connections, may indicate a loose connection. When replacing a stepper motor, driver or Driver Pack in a motion control system, be sure to inspect all terminal blocks and connectors. Check cabling/wiring for accuracy. Stress stepper motor wiring and connections for worse conditions and check with an ohmmeter.

Problem: Stepper motor wires were disconnected while the driver was powered up.
Solution: Avoid performing any service to the stepper motors or drivers while the power is on, especially in regard to motor connections. This precaution is imperative for both the driver, as well as the technician/installer.

Problem: Poor system performance.
Solution: Check to see if the wire/cables are too long. Keep wire/cable to the stepper motors under 25 feet in length. For applications where the wiring from the stepper motors to the stepper drivers exceeds 25 feet, please contact the factory for instructions, as it is likely that transient voltage protection devices will be required. Another possibility is that the stepper motor lead wires are of a gauge that is too small. Do not match your cable wires to the gauge size the stepper motor lead wires. Anaheim Automation suggests using a shielded cable for such wiring (purchased separately). Additionally, check the age of your stepper motor, as with time and use, stepper motors lose some of their magnetism which affects performance. Typically one can expect 10,000 operating hours for stepper motors (approximately 4.8 years, running one eight-hour shift per work day). Also, make certain that your stepper motor and driver combination is a good match for your application. Contact the factory, should you have any concerns.

Problem: The stepper motor has a shorted winding or a short to the motor case.
Solution: It is likely that you have a defective stepper motor. Do not attempt to repair motors. Opening the stepper motor case may de-magnetize the motor, causing poor performance. Opening of the stepper motor case will also void your warranty. The motor windings can be tested with an ohmmeter. As a rule of thumb, if the stepper motor is a frame size of NEMA 08, 11, 14, 15, 17, 23, or 34 and the warranty period has expired, it is not cost-effective to return these stepper motors for repair. Call the factory if your suspect a defective stepper motor that is still under warranty, or if it is a NEMA size 42 or a K-series motor.

Problem: The stepper motor driver or Driver Pack is over-heating.
Solution: Ventilation and cooling accommodations are essential - failure to provide adequate airflow will affect the stepper motor driver's performance and will shorten the life of the driver. Keep driver temperatures below 60 degrees Celsius. To maintain good airflow, use fans, heat sink material, and base plates, so not to exceed the maximum temperature rating of the stepper motors, drivers or controllers. Be mindful of temperatures inside cabinets and enclosures where stepper drivers may be mounted.

Problem: Environmental factors are less than ideal.
Solution: Environmental factors, such as welding, chemical vapors, moisture, humidity, dust, etc., can damage both the electronics and the stepper motors. Protect drivers, controllers and stepper motors from environments that are corrosive, contain voltage spikes, or prevent good ventilation. Anaheim Automation offers products in several line voltage ranges. For AC lines that contain voltage spikes, a line regulator (filter) will likely be required.

Problem: Pulse rates (Clock or Step) to the driver are too high.
Solution: The typical half-step driver can drive stepper motors at a maximum rate of 20,000 pulse per second. Pulse rates of above 60,000 pulses per second can damage the driver. See individual specification sheets for the motor and driver combination for best performance.

Problem: The stepper motor is stalling.
Solution: In some cases, stalling the motor causes a large voltage spike that often damages the phase transistors on the driver. Some drivers are designed to protect itself from such an occurrence. If not, Transient Suppression Devices can be added externally. Consult the factory for further information.

Problem: The stepper motor is back-driving the driver.
Solution: A stepper motor that is being turned by a load creates a back EMF voltage on the driver. Higher speeds will produce higher voltage levels. If the rotational speed gets very high, this voltage might cause damage to the driver. This is especially dangerous when the motor is back-driven while the driver is still on. Put a mechanical stop or brake in applications that might be subject to these phenomena.

General Safety Considerations for Stepper Motor Applications

The following safety considerations must be observed during all phases of operation, service and repair. Failure to comply with these precautions violates safety standards of design, manufacture, and intended use of stepper motors, drivers and controllers. Anaheim Automation, Inc. assumes no liability for the customer's failure to comply with these requirements. Even well built products, operated or installed improperly, can be hazardous. Safety precautions must be observed by the user with respect to the load and operating environment. The customer is responsible for proper selection, installation and operation of the products purchased from Anaheim Automation, Inc.

• Use caution when handling, testing, and adjusting during installation, set-up and operation • Service should not be performed with power applied • Exposed circuitry should be properly guarded or enclosed to prevent unauthorized human contact with live circuitry • All products should be securely mounted and adequately grounded • Provide adequate air flow and heat dissipation • Do not operate in the presence of flammable gases, vapors, liquids or dust

NOTE: Please Use a RMA Form should you need to return a product for REPAIR. This form can be found in Support, Forms, RMA Request on this web site.

One of Anaheim Automation Inc.'s customers provides services and products for the automobile industry, such as process automation, prototyping, engine test standards, and gauging equipment. At one point, our customer encountered a problem; popular cars were being redesigned, and they needed computer control of stepper motors for their project. They had tried several other motion control manufacturers before deciding to have Anaheim Automation help them with their project. The project dealt with the cooling of an engine in a strange area. Anaheim Automation's assignment was to construct a prototype that would scoop air from beneath the car and redirect maximum air flow to this area.

It was almost impossible to predict an accurate shape that would allow precise airflow, due to the fact that in order to fit in the available space, the duct had to be in an extremely complex configuration. The solution to this problem involved making a flexible duct that, by moving its parts, allowed it to be reshaped. The duct would be mounted in a wind tunnel, and installed in the prototype of the car. Next, engineers experimented with the duct's shape until they discovered what shape allowed for the best air flow. This shape became the basic model to construct in the overall prototype.

Anaheim Automation needed to shape the duct without diverting from the project goal, and therefore needed 15 axes of motion and one easy-to-use controller. To meet this necessity, Anaheim Automation assembled five triple-axis stepper motor drivers, programmable indexers, an interface, and the necessary power supply into a compact package, along with 15 compatible stepper motors.

When the computer was turned on, the program came up, so the system didn't require any knowledge of the computer operation. In addition, it reduced operation to simply answering three questions (prompting the user). The user could change the speed at any time; however, the operator did not need to know anything about base speed, acceleration, or deceleration, because the parameters for optimal motor speed was preloaded with the system program. While operating, the program prompted the operator with, "What axis, how many steps, and which direction?" The user only needed to press the F1 function key to produce the desired motion for the stepper motors to move.

With the experiment in full swing, engineers were able to manipulate the air duct in order to achieve maximum air flow underneath the vehicle. The required motion was easily produced at the press of a button, and the positions could be easily repeated. Ultimately, our customer's engineering staff was able to determine the exact shape of the duct that provided the car with maximum air flow. Simple, low-cost, and extremely efficient stepper motors and drivers provided the solution the customer required.

Stepper Motors are currently used all around the world for many types of applications. These motors provide as constant power devices. At low rpm's a high torque can be achieved the same cannot be said when the speed is increased. A high torque cannot be achieved at higher rpm's. These motors are great for positioning objects, such as conveyor belts, assembly lines, lathes, laser cutting, grinding and drilling machines, etc.

Stepper motors are ideal for precise positioning. You may have a fixed speed, variable speed, and position control. These motors are able to handle complex positions or movements. These devices offer power and precision in a compact sizes. These motors can take a great load. A good example to show this would be an escalator. Escalators are constantly worked and carry very heavy loads throughout the day. The step motor has to be able to take up to several hundreds of pounds maybe even thousands. The speed of the escalator is constant and never changes no matter how many people are on it.

A different type of application could be an assembly line. This typically requires precise quick and place movements. Most stepper motors are an open loop system, meaning there is no feedback info needed about the position. By keeping track of the input step pulses, the position is known.

Some of the advantages of a stepper motor, but not limited to are:
• Its input pulse is proportional to angle rotation
• If windings are energized at stand sill the motor has full torque
• Different rotation speeds are available since the frequency of input pulses are proportional to the speed.
• It cost less to have open-loop control that responds to digital input pulses
• Precise response time to starting, stopping, and reversing
• No brushes within the motor making it more reliable.


There are three different types of stepper motors to choose from, the variable -reluctance, the permanent-magnet, and last but not least the hybrid step motor. The three all have different qualities for certain applications. Stepper motors have been around for a long time and are currently and will continue to be used throughout the world. No matter what the application will be the step motor will always rise to the occasion.

Anaheim Automation's tremendous versatility of control systems is evident in their new program titled, Musical Motors. They have utilized stepper motors, stepper drivers, and stepper controllers to operate at speeds that coincide with musical notes and pitches to produce a number of different tunes. Each tune is performed by simply running the program that converts each music note into a certain step-per-second. All of the different stepper motors are programmed to produce an appropriate pitch based on how many steps-per-second they run, and for how long. Typically played at a trade show, the program provides the element of surprise; most people do not expect to hear music that is being played by stepper motors!

Stepper motors are versatile motion control components that can be applied to several different industries, from entertainment and film, to the business world, to science and medicine.

Aircraft: Stepper motors are frequently used in aircraft instruments, scanning equipment, and sensing devices, such as antennas.

Automotive: SUV's and RV's, as well as some high-end automobiles, use stepper motors to receive telecommunication signals. Stepper motors are also used for cruise control, automated dashboards gauges and electronic window equipment, as well as in automobile factories on their production lines.

Cameras - Filming and Projection: Not only do stepper motors operate filming cameras and projectors, in the entertainment industry, but automatic digital cameras and mobile phone camera modules utilize tiny stepper motors for focusing and zooming functions as well. The security industry also uses stepper motors for zooming, tilting and scanning operations in surveillance and security cameras.

Entertainment and Gaming: Slot machines, lottery machines, raffles, card shufflers, and wheel spinners can all be operated by cost-effective and reliable stepper motors. You can also find stepper motors in stage productions to control curtains and lighting functions, for plays and concerts, as well as seminars and rallies.

Laboratory and Factory Improvements and Upgrades: Stepper motors are employed to perform tedious movements pertaining to mixing chemicals in laboratories, and operating equipment for controlled environmental testing. Stepper motors are used in retrofit kits (stepper motors, drivers, controllers and power supplies) for CNC machine control, factory automation and assembly processes. Stepper motors can also be found in scientific study, used to position observatory telescopes, and in many different types of scientific equipment, i.e. spectrographs, analyzers, and diagnostic machines.

Medical: Stepper motors provide a wide variety of functions for the medical and dental world. Stepper motors are used within medical scanners, multi-axis stepper motor microscopic or nanoscopic motion control of automated devices, auto-injectors, samplers, dispensing pumps, respirators, blood analysis machinery and chromatographs. In the dental industry, stepper motors operate fluid pumps, and are often found inside digital dental photography equipment.

Office Equipment: PC based scanning equipment, optical disk drive head driving mechanisms, bar-code printers, label and box printers, scanners, and data storage drives all utilize stepper motors for their motion control operation.

Stepper motors in open-loop systems can provide accurate, dependable speed and positioning that can equal the best servo performance if installed correctly. Their simplicity allows them to function without tachometers, encoders, or other drawbacks that add to the cost of operation. Proper installation also makes it easy to pinpoint the exact effect of the operation, since they increment a precise amount with each control pulse. Likewise, the rate of control pulses determines motor speed so it too is totally predictable. Therefore, in the right mechanical environment, stepper motor systems can provide whatever degree of accuracy and reliability that is required.

Designing a System:
Stepper motors have several usage benefits over servos, the first being cost. In almost any application, stepper motors can be used at a fraction of the cost of servo. With servo drives, the problem of feedback loop phase shift and instability is common. However, stepper motors are open-loop systems that completely void any potential problem that could arise in this area.

The initial design phase for open-loop systems is similar to that of the servo system. Load characteristics, performance requirements, and mechanical design, including coupling techniques, must be thoroughly considered before a designer can effectively select the best appropriate stepper motor and driver combination for an application.

Once these factors have been determined, the motor specifications and system motion controller, such as a computer or PLC, can be established. Then the design comes down to selecting the suitable driver and controller to produce the motion necessary for the application.

Defining a Driver Pack:
In order to obtain an optimum solution, the following factors must be considered:
1. Begin with the stepper motor(s) and controller you have selected for your application.
2. Make use of one driver for each motor. The driver must match the motor current (amps per phase).
3. Include a power supply that supports the driver(s) and motor(s).
4. Select an interface to handle communications between the control device and the indexer (parallel, RS422, RS232C, serial, PLC, or manual switches).
5. Configure the Driver Pack with items 2 through 4 as applicable, or see Driver Packs on our website.

NOTE: When the wiring from a driver to a stepper motor extends beyond 25 feet, consult Anaheim Automation for additional assistance. Shielded motor cable is available and purchased separately.

Along with stepper motors, Anaheim Automation carries a comprehensive line of drivers and controllers, power supplies, gear motors, gearboxes, stepper motors linear actuators and integrated stepper motors/driver packages. Additionally, Anaheim Automation offers encoders, brakes, HMI couplings, cables and connectors, linear guides and X-Y tables. If the stepper motors is not ideal for your application, you might consider brushless DC, brush DC, servo, or AC motors, and their compatible drivers/controllers.

• Cost-effective
• Simple designs
• High reliability
• Brushless construction
• Maintenance-free
• If windings are energized at standstill, the motor has full torque
• No feedback mechanisms required
• High acceleration and power rate
• A wide range of rotational speeds can be attained as the speed is proportional to the frequency of the input pulses
• Known limit to the dynamic position error

Stepper motors vary in cost based on the criteria for each application. Some criteria include options of 0.9°, 1.8°, 3.6° and 4.5° step angles, torque ranging from 1 to 5,700 oz-in, and NEMA frame sizes of 08 to 42. Additional attachments such as cables and encoders can be purchased separately for an additional cost. With our friendly customer service and professional application assistance, Anaheim Automation often surpasses customer expectations for fulfilling specific stepper motors and driver requirements, as well as other motion control needs.

Each type of stepper motors varies per application by its construction and functionality. The three most common stepper motors types are Variable Reluctance, Permanent Magnet, and Hybrid Stepper Motors.

Variable Reluctance (VR) Stepper Motors
VR stepper motorss are characterized as having multiple soft iron rotors and a wound stator. VR stepper motors generally operate on the basic principle of the magnetic flux finding the lowest reluctance pathway through a magnetic circuit. In general operation, VR stepper motorss have relatively high step rates of 5 to 15 degrees and have no detent torque. The step angles taken in VR stepper motors are related to the number of teeth the stator and rotor have. The equation relating these two variables can be found in the formula section of this guide.

How Does a Variable Reluctance Stepper Motors Work?
Referring to Figure 1 on Page 2, the poles become magnetized when the stator windings are energized with DC current. With the poles becoming magnetized, the rotor teeth are now attracted to the energized stator poles and rotate to line up. With the windings around stator A becoming energized the rotor teeth become attracted allowing the poles to line up. When A’s windings become de-energized and B’s windings become energized, the rotor rotates to line its teeth with the stator teeth. This process continues in sequence with C, followed by D being energized allowing for the rotor to rotate.

Brief Summary of Variable Reluctance Stepper Motors:
• The rotor has multiple soft iron rotors with a wound stato
• Least complex and expensive stepper motors
• Large step angles
• No detent torque detected in hand rotation of a de-energized motor shaft

Permanent Magnet (PM) Stepper Motors
PM stepper motorss are comprised of permanent magnet rotors with no teeth, which are magnetized perpendicular to the axis of rotation. By energizing the four phases in sequence, the rotor rotates due to the attraction of magnetic poles. The stepper motors shown in Figure 2 on page 3 will take 90 degree steps as the windings are energized in clockwise sequence: ABAB. PM stepper motorss generally have step angles of 45 or 90 degrees and step at relatively low rates. However, they exhibit high torque and good damping characteristics. Anaheim Automation carries a wide selection of PM stepper motorss, ranging from 15 to 57mm in diameter.

Brief Summary of Permanent Magnet (PM) Stepper Motors:
• The rotor is a permanent magne
• Large to moderate step angle
• Often utilized in computer printers as a paper feeder

Hybrid Stepper Motors
Hybrid stepper motors incorporate the qualities of both the VR and PM stepper motors designs. With the Hybrid stepper motors’s multi-toothed rotor resemblance of the VR, and an axially magnetized concentric magnet around its shaft, the Hybrid stepper motors provides an increase in detent, holding and dynamic torque. In comparison to the PM stepper motors, the Hybrid stepper motors provides performance enhancement with respect to step resolution, torque, and speed. In addition, the Hybrid stepper motors is capable of operating at high stepping speeds. Typical Hybrid stepper motorss are designed with step angles of 0.9°, 1.8°, 3.6° and 4.5°; 1.8° being the most common step angle. Hybrid stepper motors are ideally suited for applications having stable loads with speeds under 1,000 rpm. There are key components which are influential of the running torque of a Hybrid stepper motors which are laminations, teeth and magnetic materials. Increasing the amount of laminations on the rotor, precision and sharpness of the rotor and stator teeth, and strength of magnetic material are all factors taken into account in providing optimal torque output for Hybrid stepper motors.

Brief Summary of Hybrid Stepper Motors:
• Smaller step angles in comparison to VR and PM stepper motors
• Rotor is made of a permanent magnet with fine teeth
• Increase in detent, holding and dynamic torque
&bull 1.°° is the most common step angle


NOTE: At Anaheim Automation, the 1.8 degree Hybrid stepper motors is the most widely stocked stepper motors type, ranging in NEMA frame sizes, 08 to 42. The Hybrid stepper motors can also be driven two phases at a time to yield more torque, or alternately one then two then one phase, to produce half-steps or 0.9 degree increments.

• Low efficiency (Stepper motors attract a substantial amount of power regardless of the load)
• Torque drops rapidly with speed (torque is inversely proportional of speed)
• Prone to resonance* (Microstepping allows for smooth motion)
• No feedback to indicate missed steps
• Low torque-to-inertia ratio
• Cannot accelerate loads very rapidly
• Motor gets very hot in high performance configurations
• Motor will not “pick up” after momentary overload
• Motor is noisy at moderate to high speeds
• Low output power for size and weight

Resonance-is inherent in the design and operation of all stepping motors and occurs at specific step rates. It is the combination of slow stepping rates, high rotor inertia, and elevated torque which produce ringing as the rotor overshoots its desired angular displacement and is pulled back into position causing resonance to occur. Adjusting either one of the three parameters –inertial load, step rate, or torque- will reduce or eliminate resonance. In practical practice, the torque parameter is more controllable using microstepping. In microstepping mode, power is applied to the stator windings incrementally which causes torque to slowly build, reducing overshoot and therefore reducing resonance.

The following environmental and safety considerations must be observed during all phases of operation, service and repair of stepper motors system. Failure to comply with these precautions violates safety standards of design, manufacture and intended use of the stepper motors, driver and controller. Please note that even with a well?built stepper motors, products operated and installed improperly can be hazardous. Precaution must be observed by the user with respect to the load and operating environment. The customer is ultimately responsible for the proper selection, installation, and operation of the stepper motors system.

The atmosphere in which stepper motors is used must be conducive to good general practices of electrical/electronic equipment. Do not operate the stepper motors in the presence of flammable gases, dust, oil, vapor or moisture. For outdoor use, the stepper motors, driver and controller must be protected from the elements by an adequate cover, while still providing adequate air flow and cooling. Moisture may cause an electrical shock hazard and/or induce system breakdown. Due consideration should be given to the avoidance of liquids and vapors of any kind. Contact the factory should your application require specific IP ratings. It is wise to install the stepper motors, driver and controller in an environment which is free from condensation, dust, electrical noise, vibration and shock.

Additionally, it is preferable to work with the stepper motors/driver /controller system in a non?static, protective environment. Exposed circuitry should always be properly guarded and/or enclosed to prevent unauthorized human contact with live circuitry. No work should be performed while power is applied. Don’t plug in or unplug the connectors when power is ON. Wait for at least 5 minutes before doing inspection work on the stepper motors system after turning power OFF, because even after the power is turned off, there will still be some electrical energy remaining in the capacitors of the internal circuit of the stepper motors driver.

Plan the installation of the stepper motors, driver and/or controller in a system design that is free from debris, such as metal debris from cutting, drilling, tapping, and welding, or any other foreign material that could come in contact with circuitry. Failure to prevent debris from entering the stepper motors system can result in damage and/or shock.

The following safety considerations are required to be observed during all phases of operation, service and repair. Failure to conform with these safety measures violates safety standards of design, manufacture, and designated use of Stepper Motors, drivers and controllers. Anaheim Automation, Inc. assumes no responsibility for the customer's incapacity to comply with theserequirements. Even well-built products, operated or installed improperly, can be hazardous. Safety precautions must be observed by the user with regard to the load and operating environment. The customer is liable for appropriate selection, installation and operation of the products purchased from Anaheim Automation, Inc.

• Use caution when handling, testing, and adjusting during installation, set-up and operation
• Service must not be performed with power applied
• Make sure the motor/driver has plenty of heat dissipation and air flow
• Exposed circuitry should be properly guarded or enclosed to counteract unauthorized human contact with live circuitry
• All products should be firmly mounted and effectively grounded
• Elements such as flammable gases, vapors, liquids or dust should not interact with motors in operation

NOTE: Please Use a RMA Form should you need to return a product for REPAIR. This form can be found in Support, Forms, RMA Request on this web site.

A stepper motors perform the conversion of logic pulses by sequencing power to the stepper motors windings; generally, one supplied pulse will yield one rotational step of the motor. This precision is provided by a stepper driver, which is able to control speed and positioning of the stepper motors. The stepper motors increment a precise amount with each control pulse, converting digital information into exact incremental rotation without the need for feedback devices, such as tachometers or encoders. Since the stepper motors/driver is an open-loop system, the problems of feedback loop phase shift and resultant instability, common with servo motor/drive systems, are eliminated.

The main use of stepper motors is to control motion, whether it is linear or rotational. In the case of rotational motion, receiving digital pulses in a correct sequence allows the shaft of a stepper motor to rotate in discrete step increments. A pulse (also referred to as a clock or step signal) used in a stepper motor system can be produced by microprocessors, timing logic, a toggle switch or relay closure. A train of digital pulses translates into shaft revolutions. Each revolution requires a given number of pulses and each pulse equals one rotary increment or step, which is only a portion of one complete rotation. There are numerous relationships between the motors shaft rotation and input pulses. One such relationship is the direction of rotation and the sequence of applied pulses. With proper sequential pulses being delivered to the device, the rotation of the shaft motor will undergo a clockwise or counterclockwise rotation. Another relation between the motor’s rotation and input pulses is the relationship between frequency and speed. Increasing the frequency of the input pulses allows for the speed of the motor shaft rotation to increase.

There are several important criteria involved in selecting the proper stepper motors:
1. Desired Mechanical Motion
2. Speed Required
3. Load
4. Stepper Mode
5. Winding Configuration

With appropriate logic pulses, stepper motorss can be bi-directional, synchronous, provide rapid acceleration, run/stop, reversal, and can interface easily with other digital mechanisms. Characterized as having low-rotor moment of inertia, no drift, and a noncumulative positioning error, a stepper motors is a cost-effective solution for many motion control applications. Generally, stepper motors are operated without feedback in an open-loop fashion and sometimes match the performance of more expensive DC Servo Systems. As mentioned earlier, the only inaccuracy associated with a stepper motors are a noncumulative positioning error measured in % of step angle. Typically, stepper motorss are manufactured within a 3-5% step accuracy.

Motion requirements, load characteristics, coupling techniques, and electrical requirements need to be understood before the system designer can select the best stepper motors/driver/controller combination for a specific application. While not a difficult task, several key factors need to be considered when determining an optimal stepper motors solution. The system designer should adjust the characteristics of the elements under his/her control, to meet the application requirements. Anaheim Automation offers many options in its broad line of stepper motors products, allowing for the maximum amount of design flexibility. Although it may appear overwhelming to choose, the result of having a large number of options is a high-performance system that is cost-effective. Elements needed to be considered include the stepper motors, driver, and power supply selections, as well as the mechanical transmission, such as gearing or load weight reduction through the use of alternative materials. Some of these relationships and system parameters are described in this guide.

Inertial Loads
Inertia is a measure of an object’s resistance to a change in velocity. The larger an object’s inertia, the greater the torque is required to accelerate or decelerate it. Inertia is a function of an object’s mass and shape. A system designer may wish to select an alternative shape or low-density material for optimal performance. If a limited amount of torque is available in a selected system, then the acceleration and deceleration times must increase. For most efficient stepper motors systems, the coupling ratio (gear ratio) should be selected so the reflected inertia of the load is equal to, or greater than, the rotor inertia of the stepper motors. It is recommended that this ratio not be less than 10 times the rotor inertia. The system design may require the inertia to be added or subtracted by selecting different materials or shapes of the loads.

NOTE: The reflected inertia is reduced by a square of the gear ratio, and the speed is increased by a multiple of the gear ratio.

Frictional Loads
All mechanical systems exhibit some frictional force. The designer of a stepper motors system must be able to predict elements causing friction within the system. These elements may be in the form of bearing drag, sliding friction, system wear, or the viscosity of an oil filled gear box (temperature dependent). A stepper motors must be selected that can overcome any system friction and still provide the necessary torque to accelerate the inertial load.

NOTE: Some friction is desired, since it can reduce settling time and improve performance.

Positioning Resolution
The positioning resolution required by the application may have an effect on the type of transmission used, and/or selection of the stepper motors driver. For example: A lead screw with 5 threads per inch on a full-step drive provides 0.001 inch/step; half-step provides 0.0005 inch/step; a microstep resolution of 25,400 steps/rev provides 0.0000015 inch/step.

The typical lifetime for stepper motors is 10,000 operating hours. This approximates to 4.8 years; given the stepper motors operates one eight-hour shift per day. The lifetime of stepper motors may vary in regards to user application and how rigorous the stepper motors are run.

Stepper motors are wound on the stator poles in either a unifilar or bifilar configuration. The term unifilar winding refers to the winding configuration of the stepper motors where each stator pole has one set of windings; the stepper motors will have only 4 lead wires. This winding configuration can only be driven from a bipolar driver. The term bifilar winding refers to the winding configuration of stepper motors where each stator pole has a pair of identical windings; the stepper motors will have either 6 or 8 lead wires, depending on termination. This type of winding configuration simplifies operation in that transferring current from one coil to another, wound in the opposite direction, will reverse the rotation of the motor shaft. Unlike the unifilar winding which can only work with a bipolar driver, the bifilar winding configuration can be driven by a unipolar or bipolar driver.

The main components used in stepper motors are the shaft, rotor and stator laminations, magnets, bearings, copper wires and lead wires, washers, and front and end covers. Most shafts of stepper motors are made of stainless steel metal, while the stator and the rotor laminations are comprised of silicon steel. The silicon steel allows for higher electrical resistivity which lowers core loss. The various magnets available in stepper motorss allow for multiple construction considerations. These magnets are ferrite plastic, ferrite sintered and Nd-Fe-B bonded magnets. The bearings of stepper motors vary with size of the motor. The housing materials are composed of various other metals like aluminum, which allow for high resistance to heat.

• Stepper motors are constant power devices.
• As the stepper motors speed increases, torque decreases.
• Maximum torque for most stepper motors is when the motor is stationary, but the important aspect of stepper motors is the torque when rotating (spinning).
• Torque curves (performance curve of specific stepper motors) can be extended by current limiting step motor drivers (see our web site for compatible stepper motors and driver models).
• Step motors exhibit some vibratory characteristics, more than other motor types. (If vibration is a problem, consider another technology).
• The vibration seen in stepper motors is due to the fact that the takes discrete steps and this tends to create a snap in the step motor rotor, as it moves from one position to the other.
• Proper sizing and pairing the stepper motors with the step motor driver will help reduce vibration
• Failure to correctly size a stepper motors application can cause the motor to lose torque and change direction, at certain speeds. (This problem can be greatly reduced or eliminated by accelerating quickly the speeds that are problematic. Frictional damping the step motor system or using a micro step motor driver combination may completely solve this problem.
• Stepper motors that are constructed with a high amount of phases are capable of smoother operation, or the same effect can be accomplished using a microstep drive technique.

Anaheim Automation carries a broad line of stepper motors, as well as step motor drivers and controller. Specials and customization services are also available, should your application require an exact step motor specification.

Have you wondered why Anaheim Automation carries the most stock in the eight-lead stepper motors configuration than the six or four lead configurations? Eight-lead stepper motors arewound like unipolar stepper motors, but the difference is that the leads are not connected (joined) to the common internally to the motor. The flexibility of the eight-lead stepper motors is in that it can be configured in several different ways:

• Unipolar
• Bipolar with single winding per phase, which will run the stepper motors on half of the windings available, reducing the available low speed torque, but requires less current to operate.
• Bipolar with SERIES windings, which provides higher inductance, but lower current per winding
• Bipolar with PARALLEL windings, which requires a higher current, but outperforms because the winding inductance is reduced.

The many configurations of the eight-lead stepper motors make it a logical choice for Anaheim Automation to stock, as it is cost-effective to manufacture and serves a wide range of customers and stepper motors applications.

Electric motors are typically classified by motor type, i.e. Alternating Current (AC) versus Direct Current (DC). This distinction is not always so rigid, in that many classic DC motors run on AC power. This type of electric motor is referred to as universal motors.

Some industries used the rated output power specification of the motor to categorize motor types. For example, those motor of less than 746 Watts are often referred to as fractional horsepower (FHP). In more recent years, the trend toward electronic control further muddles the electric motor distinctions, as modern motor drivers and controllers have moved the commutator out of the motor casing. For this newer type of motors, driver and controller circuits are relied upon to generate sinusoidal AC drive currents. Examples of such are: the Blushless DC Motor (BLDC) and the Stepper Motors, both being poly-phase AC motors requiring external electronic control. Although historically, stepper motors (such as for maritime and naval gyrocompass repeaters) were driven from DC switched by contacts.

Considering all rotating (or linear) electric motors require synchronism between a moving magnetic field and a moving current sheet for average torque production, there is a clearer distinction between an asynchronous and synchronous types. An asynchronous motor requires slip between the moving magnetic field and a winding set to induce current in the winding set by mutual inductance; the most ubiquitous example being the common AC Induction Motor which must slip to generate torque. In the synchronous types, induction (or slip) is not a requisite for magnetic field or current production. See the chart below to help determine if a stepper motors, Brush or BLDC motor, AC or Servo is the correct motor choice for your application.

Stepper motors are a component used in functions pertaining to open loop positioning and velocity. Ultimately, the system's accuracy depends on the stepper motors and the drive's precision and behavior, because there is not feed-back transducer.

Microstepping, precision sine/cosine current references, and second order damping have allowed the stepper motors to become the ideal candidate for applications dealing with precision control. Disregarding the drive, the stepper motors has distinct qualities that must be considered in regard s to accuracy in any application.

Stepper motors are assembled to a certain tolerance. Usually, a standard stepper motors has a tolerance of +/- 3% non accumulative error regarding any step's location. In other words, on a typical 200 step per revolution stepper motors, teach step will be within 0.18-degree error range. The stepper motors can essentially resolve 2000 radial locations, accurately. Incidentally, this is the 10 microstep drive's resolution.

Beyond the resolution of 10, i.e. 125, there is no real additional accuracy (there may be more smoothness, but no increase in accuracy). Similarly, a voltmeter that displays 6 digits while having 1% accuracy only contains significant information in the first two digits. Two exceptions allow for higher resolutions: stepper motors that run in a closed-loop application with a high-resolution encoder, or an application that needs to operate smoothly at extremely low speeds (fewer than 5 full steps per second).

Motor linearity is another factor that affects accuracy. Motor linearity is how the stepper motors operates between step locations. For every step pulse sent to a 10 microstep drive, a typical 1.8 per step motor should move precisely 0.18 degrees. All stepper motors faces non-linearity; microsteps refuse to evenly spread themselves over a full step, and instead bunch together. Typically two effects may occur: deceleration where the microsteps bunch up and cyclic acceleration where the microsteps spread apart cause dynamically low speed resonances. Statically, the stepper motors position is not optimum.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Q: What is an encoder? A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion. Q: What is the difference between absolute and incremental encoders? A: Absolute and incremental encoders are different in two ways: - Every position of an absolute encoder is unique - An absolute encoder never loses its position due to power loss or failure. Incremental encoders lose track of position upon power loss or failure Q: What is a channel? A: A channel is an electrical output signal from an encoder. Q: What is a quadrature? A: A quadrature has two output channels, with repeating squarewaves, which are out of phase by 90 electrical degrees. From the phase difference, the direction of rotation can also be determined. Q: What is an index pulse? A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution. Q: What other types of encoder technologies are there? A: There are two types of encoder technologies. - Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk. - Magnetic: Strips of magnetized material are placed on rotating discs and are sensed by Hall-Effect Sensors or magneto-resistive sensors. Q: What types of applications are encoders implemented in? A: They are frequently utilized in stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback. Q: Does any encoder disk (codewheel) work with any encoder module? A: No, each resolution and each disk diameter works with a different encoder module. Q: What is PPM? A: PPM stands for pulse per revolution in rotational motion for rotational motion and pulse per inch or millimeter for linear motion. Q: When can a single output channel be used in an incremental encoder? A: A single output channel for an incremental encoder can be used when it is not important to sense direction. Such applications make use of tachometers.

Although the bipolar step motor has been overshadowed in the past by servo systems for motion control, it has emerged as the preferred technology in more and more areas. The major factor in this trend towards the bipolar step motor is the prevalence of digital control, the emergence of the microprocessor, improved designed (i.e. high?torque models), and lower cost. Today, bipolar step motor applications are all around us: they are used in printers (paper feed, print wheel), disk drives, clocks and watches, as well as used in factory automation and machinery. A bipolar step motor is most often found in motion systems requiring position control. Anaheim Automation’s cost?effective bipolar step motor product line is the wise choice for both OEM and user accounts. Anaheim Automations customers for the bipolar step motor product line is diverse: industrial companies operating or designing automated machinery or processes involving food, cosmetics or medical packaging, labeling or tamper?evident requirements, cut?to?length applications, assembly, conveyor, material handling, robotics, special filming and projection effects, medical diagnostics, camera tracking, inspection and security devices, aircraft controls, pump flow control, metal fabrication (CNC machinery), and equipment upgrades. Anaheim Automation, Inc. bipolar step motor product line integrates a matched bipolar step motor, driver and controller in one unit. This design concept makes selection easy, thus reducing errors and wiring time. With friendly customer service and professional application assistance, Anaheim Automation often surpasses the customers expectations for fulfilling specific bipolar step motor and driver requirements, as well as other motion control needs. Bipolar Step Motors are Used in Many Industries Stepper motors have become an essential component to applications in many different industries. The following is a list of industries making use of bipolar step motors: • Aircraft – In the aircraft industry, bipolar step motors are used in aircraft instrumentations, antenna and sensing applications, and equipment scanning • Automotive – The automotive industry implements bipolar step motors for applications concerning cruise control, sensing devices, and cameras. The military also utilizes bipolar step motors in their application of positioning antennas • Chemical – The chemical industry makes use of bipolar step motors for mixing and sampling of materials. They also utilize bipolar step motor controllers with single and multi-axis bipolar step motors for equipment testing • Consumer Electronics and Office Equipment – In the consumer electronics industry, bipolar step motors are widely used in digital cameras for focus and zoom functionality features. In office equipment, bipolar step motors are implemented in PC-based scanning equipment, data storage drives, optical disk drive driving mechanisms, printers, and scanners • Gaming – In the gaming industry, bipolar step motors are widely used in applications like slot and lottery machines, wheel spinners, and even card shufflers • Industrial – In the industrial industry, bipolar step motors are used in automotive gauges, machine tooling with single and multi-axis bipolar step motor controllers, and retrofit kits which make use of bipolar step motor controllers as well. Stepper motors can also be found in CNC machine control • Medical – In the medical industry, bipolar step motors are utilized in medical scanners, microscopic or nanoscopic motion control of automated devices, dispensing pumps, and chromatograph auto-injectors. Stepper motors are also found inside digital dental photography (X-RAY), fluid pumps, respirators, and blood analysis machinery, centrifuge • Scientific Instruments –Scientific equipment implement bipolar step motors in the positioning of an observatory telescope, spectrographs, and centrifuge • Surveillance Systems – Stepper motors are used in camera surveillance

A bipolar step motor (also referred to as a step or stepping motor) is an electromechanical device achieving mechanical movements through conversion of electrical pulses. Stepper motors are driven by digital pulses rather than by a continuous applied voltage. Unlike conventional electric motors which rotate continuously, bipolar step motors rotate or step in fixed angular increments. A bipolar step motor is most commonly used for position control. With a bipolar step motor/driver/controller system design, it is assumed the bipolar step motor will follow digital instructions. One important aspect of bipolar step motors is their lack of feedback to maintain control of position. It is this lack of feedback which classifies bipolar step motors as open-loop systems.

Bipolar Step Motor products are a type of digital device. Digital information is processed through the Bipolar Step Motor products to accomplish an end result, in this instance, controlled motion.You can assume that Bipolar Step Motor products will dependably follow digital instructions just as a computer is anticipated to. This is the unique feature for Stepper motors. Bipolar Step Motor products are an electric power motor that is driven by digital pulses as opposed to a continuously applied voltage. Inherent in this concept is open-loop control, where a train of pulses converts into so many shaft revolutions, with each revolution requiring a given number of pulses. Each pulse equals one rotary increment, or step (hence, Stepper motors), which is only a portion of one finished rotation. As a result, counting pulses can be applied in Bipolar Step Motor products to accomplish a ideal amount of shaft rotation. The count automatically represents how much movement has been achieved, without the demand for feedback information, as would be the instance in servo systems.

Q: Why is the bipolar step motor size important? Is it possible to just choose a large motor size? A: The bipolar step motor size is important because if the motor’s rotor inertia predominately consists of the load, resonance increases and poses issues. Also, larger rotors require more time to accelerate and decelerate and therefore it is important to choose a motor size dependent on the criteria for user applications. Q: While increasing speed, why do bipolar step motors lose torque? A: Inductance is the leading cause for motors losing torque at high speeds. The electrical time constant, ?, is the amount of time it takes a motor winding to charge up to 63% of its rated value given a resistance, R, and inductance, L. With ? = R/L, at low speeds, high inductance is not an issue since current can easily flow through the motor windings quickly. However, at high speeds, sufficient current cannot pass through the windings quick enough before the current is switched to the next phase, thereby reducing the torque provided by the motor. Therefore, it is the current and number of turns in the windings which determines the maximum output torque in a motor, while the applied voltage to the motor and the inductance value of the winding will affect on the speed at which a given amount of torque can be produced. Q: Why does increasing the voltage increase the torque if bipolar step motors are not voltage driven? A: Voltage can be viewed as forcing current through the coil windings. By increasing voltage, pressure to force current through the coil also increases. Therefore, this vast amount of current being forced through the coil causes it to saturate which results in loss of torque and increase of speed. Q: What temperatures are bipolar step motors able to run at? A: Most bipolar step motors include Class B insulation. This allows the motor to sustain temperatures of up to 130° C. Therefore, with an ambient temperature of 40° C, the bipolar step motor has a temperature rise allowance of 90° C allowing for bipolar step motors to run at high temperatures. Q: Is it possible to get more torque by running the bipolar step motor at double its rated current? A: It is possible to increase torque by increasing the current but by doing so, it weakens the motor’s ability to run smoother. Q: What is the difference between four, six and eight leads in motors? A: Stepper motors have the capability to run in either parallel or series modes. In a parallel mode, only a four lead motor can be run while in a series mode a six lead motor can be run. Eight lead motors can run in either parallel or series configurations. In applications where more torque is required at higher speeds, a lower inductance value given from a four lead motor is better choice. Q: What is the difference between Unipolar and Bipolar motors? A: A unipolar wound motor has six lead wires with each winding having a center tap. Most applications implementing unipolar wound motors require high speed and torque. On the other hand, a bipolar wound motor has four lead wires with having no center tap connections. Most applications implementing bipolar wound motors require high torque at low speeds. Q: What is the difference between a closed-loop bipolar step motor controller and an open-loop bipolar step motor controller? A: In an open-loop bipolar step motor controller, no feedback is going from the motor to the controller. This type of controller is effective when the motor is carrying a constant load at a steady speed. A closed-loop motor controller is more applicable in applications where load or speed varies. In comparison to the closed-loop controller, the open-loop controller lacks complexity and is more affordable. Q: When should I use microstepping? A: Microstepping is typically used in applications which require the motor to operate at less than 700 pulses per second.

Stepper motors are driven by waveforms which approximate to sinusoidal waveforms. There are three excitation modes commonly used with bipolar step motors which are full?step, half?step and microstepping. Bipolar Step Motor ? Full?Step (Two Phases are on) In full?step operation, the bipolar step motor steps through the normal step angle, e.g. with a 200 step/revolution the motor rotates 1.8° per full step, while in half?step operation the motor rotates 0.9° per full step. There are two kinds of full?step modes which are single-phase full-step excitation and dual-phase full-step excitation. In single-phase full?step excitation, the bipolar step motor operates with only one phase energized at a time. This mode is typically used in applications where torque and speed performances are less important, wherein the motor operates at a fixed speed and load conditions are well defined. Typically, bipolar step motors are used in full?step mode as replacements in existing motion systems, and not used in new developments. Problems with resonance can prohibit operation at some speeds. This mode requires the least amount of power from the drive power supply of any of the excitation modes. In dual-phase full?step excitation, the bipolar step motor operates with two phases energized at a time. This mode provides excellent torque and speed performance with minimal resonance problems. NOTE: Dual excitation provides about 30 to 40 percent more torque than single excitation, but does require twice the power from the drive power supply. Many of Anaheim Automation’s microstepping drivers can be set to operate at full?step mode if necessary. Bipolar Step Motor ? Half?Step Stepper motor half?step excitation mode alternates between single and dual-phase operations resulting in steps that are half the normal step size. Therefore, this mode provides twice the resolution. While the motor torque output varies on alternate steps, this is more than offset by the need to step through only half the angle. This mode had become the predominately used mode by Anaheim Automation beginning in the 1970’s, because it offers almost complete freedom from resonance issues. The bipolar step motor can operate over a wide range of speeds and drive almost any load commonly encountered. Although half?step drivers are still a popular and affordable choice, many newer microstepping drivers are cost?effective alternatives. Anaheim Automation’s BLD75 series is a popular half-step driver and is suitable for a wide range of bipolar step motors. Bipolar Step Motor ? Microstepping In the bipolar step motor microstepping mode, a bipolar step motors natural step angle can be partitioned into smaller angles. For example: a conventional 1.8 degree motor has 200 steps per revolution. If the motor is microstepped with a divide?by?10, then each microstep moves the motor 0.18 degrees, which becomes 2,000 steps per revolution. The microsteps are produced by proportioning the current in the two windings according to sine and cosine functions. This mode is widely used in applications requiring smoother motion or higher resolution. Typical microstep modes range from divide?by?10 to divide?by?256 (51,200 steps per revolution for a 1.8 degree motor). Some microstep drivers have a fixed divisor, while the more expensive microstep drivers provide for selectable divisors. For cost?effective microstep drivers, see Anaheim Automation’s MBC and MLA Series. NOTE: In general, the larger the microstep divisor provided, the more costly will be the bipolar step motor driver. Should you prefer, Anaheim Automation also manufactures a series of Integrated Bipolar Step Motors/Drivers, meaning the bipolar step motor and driver are in one unit. This design approach takes the guesswork out of motor and driver compatibility. For more information, please see the 17MD, 23MD and 34MD Series.

Bipolar Step Motor products have three often affiliated excitation modes. The Bipolar Step Motor modes include the full-step, half-step and micro-step. Bipolar Step Motor - Full-Step: In whole step operation, Bipolar Step Motor products step in the normal step angle e.g. 200 step/revolution motors take 1.8 steps while in half step operation, 0.9 steps are taken. There are two kinds of full-step modes. Single phase full-step excitation is when Bipolar Step Motor products are run with only one phase energized at a time. This mode must only be used where the motor is operated with load conditions that are well defined and at a fixed rate, such as where torque and speed performance is not essential. Difficulties with resonance can stop operation at some speeds. This unique form of mode requires the least amount of power from the drive power supply of any of the excitation modes. Dual phase full-step excitation is simply when the Bipolar Step Motor products are controlled with two phases energized at-a-time. Other than its small amount of resonance problems, this mode provides good torque in addition to speed performance. Dual excitation requires double the power from the drive power supply, but provides about 30-40% extra torque than single excitation. Bipolar Step Motor - Half-Step: The option for half-step excitation in Bipolar Step Motor products provides two times the resolution. It results in steps that are add up to one half of the normal step size by usingalternative single and dual phase operation. This setting is great because the motor only needs to step through only have the angle, even though the motor torque end result varies on alternate steps. This mode is becoming the predominately used mode by Anaheim Automation because it offers almost complete freedom from resonance problems. Bipolar Step Motor products are usually operated over a wide range of speeds and also used to drive almost any kind of load commonly experienced. Bipolar Step Motor - Micro-Step: Within Bipolar Step Motor products micro-step mode, a Bipolar Step Motors natural step angle can be divided into much smaller angles. To show this, the 200 steps per revolution that natural Stepper motors begin with (1.8°) can be divided by 10 if it is micro-stepped; therefore creating 2,000 steps per revolution with each micro-step equalling 0.18°. For a 1.8° motor, if there are 51,200 steps per revolution, then micro-step modes can range from being divided by 10 to to be divided by 256. The micro-steps are maded by proportioning the current in the two windings relating to sine and cosine functions. This mode is entirely used where smoother motion or more resolution is essential.

Stepper motors are wound on the stator poles in either a unifilar or bifilar configuration. The term unifilar winding refers to the winding configuration of the bipolar step motor where each stator pole has one set of windings; the bipolar step motor will have only 4 lead wires. This winding configuration can only be driven from a bipolar driver. The term bifilar winding refers to the winding configuration of a bipolar step motor where each stator pole has a pair of identical windings; the bipolar step motor will have either 6 or 8 lead wires, depending on termination. This type of winding configuration simplifies operation in that transferring current from one coil to another, wound in the opposite direction, will reverse the rotation of the motor shaft. Unlike the unifilar winding which can only work with a bipolar driver, the bifilar winding configuration can be driven by a unipolar or bipolar driver.

Because Bipolar Step Motor products fluctuate in the way they perform and the way they are constructed, they are broken down into three basic varieties. Each of these designs of Bipolar Step Motor products offers an alternative to an application in a different way. The three basic types of Bipolar Step Motor products consist of the Variable Reluctance, Permanent Magnet, and Hybrid. Variable Reluctance (VR) Bipolar Step Motor products: Variable Reluctance Bipolar Step Motor products are recognized for possessing soft iron multiple rotor and a wound stator. The Variable Reluctance Bipolar Step Motor products hold no detent torque. They typically operate in step angles from 5 to 15° at fairly high step rates. The four teeth line up with the four stator teeth of phase A by magnetic attraction when phase A is stimulated; as shown in figure 5. The next step is taken when A is switched off and phase B is energized, spinning the rotor clockwise 15°; Continuing the sequence, C is turned on next and then A again. If you change it so that the phase arrangement is reversed, the rotation will rotate counter clockwise. Permanent Magnet (PM) Bipolar Step Motor products: The second type of Bipolar Step Motor products are classified as the Permanent Magnet Stepper motors.These Bipolar Step Motor products are diverse from the other two due to the fact that they have permanent magnet rotors and no teeth; the rotors are magnetized perpendicular to the axis. The rotor is attracted to the magnetic poles and as a result it rotates, when the four phases are energized in sequence. The motor will take 90 degree steps as the windings are energized in sequence ABCD, as shown in Figure 6. Permanent Magnet Bipolar Step Motor products generally have step angles of 45 to 90 degrees and have a tendency to step at relatively low rates, but generate high torque and excellent damping characteristics. Hybrid Bipolar Step Motor products: Hybrid Bipolar Step Motor products combine qualities from the permanent magnet as well as variable reluctance Bipolar Step Motor products. Here are some likable features of Hybrid Bipolar Step Motor products which are from each: These Bipolar Step Motor products have an exceptional holding and dynamic torque, a high detent torque, and theyll operate in high Stepper speeds. Step angles of 0.9 to 5.0 degrees are normally seen in Hybrid Bipolar Step Motor products. In order for a single power supply to be used to power the motor, Bi-filar windings are supplied to these Bipolar Step Motor products. The rotor should rotate in increments of 1.8 degrees if the phases are energized one at a time in the order they are indicated at. These Bipolar Step Motor products may be driven in two phases at a time to yield more torque. Hybrid Bipolar Step Motor products can be be driven by one then two then one phase to make half steps of 0.9 degree increments.

Often customers want plastic extrusion shops to do precision cutting on top of producing extrusions. However until recently, many requests of that nature had to be declined, or the shops had to invest in machines that cost up to $125,000. Recently however, one shop solved this problem by developing an automated Precision Cutter, a machine that holds the close tolerances required, cuts both hard and soft extrusions, also does counterboring and reaming, and costs less than $35,000. With its capability at this price, precision extrusion cutting became a high-return secondary operation for any extrusion shop. The Precision Cutter essentially consisted of a single-axis positioning table, an air-raised-gravity-dropped cutoff saw, and air-operated clamps. An Anaheim Automation Programmable Bipolar Step Motor Driver Pack (which included stepper motor drives and controllers), and an easy-to-use computer program worked together to provide control. In operation, an extrusion was clamped on the Precision Cutters locating table and a stepping motor fastened to the table, so the programmed length extends beyond the cutoff saw. The extrusion and parts that will be cut are secured by clamps on either side of the blade. This clamping ensemble eliminated part movement during the cutting process and made sure the required tolerance-down to the plus or minus 0.002 in.-will be met. The blade completed the cut and then returned to its original position. After this function, the clamps released the cut part and re-positioned the extrusion for the next area to be cut. The computer used for programming was housed in a drawer on the machine. For cutting, the programmer only needs to key in one number. However, if counterboring and reaming were also required, the operator must key in three numbers. Once the operator presses the RESET button, the machine began to cycle through the program until it ran out of material. Computer commands were sent to both the Bipolar Step Motor Driver Pack and the inputs from the sensors on the machine. Anaheim Automation developed an internal program that provided instructions for the stepper motor drives to translate the information into the necessary driver output to operate the stepping motor. The stepping motor positioned the table, and sent the information to output signals that operate the air solenoids that controlled the clamps and the jaw. The bipolar stepper motor Driver Pack chosen contained stepper motor drives, computer interface and the necessary logic it needed to translate machine signals and computer input into pulses. These pulses operated one or more stepper motors and controlled signals for beginning and ending the necessary mechanical processes. High-performance, bi-level stepper motor drives (one for each motor) were the chosen driver(s). A fan-cooled power supply, specifically matched to the requirements of the stepper motor drives and was also included in the bipolar stepper motor Driver Pack. Bipolar Step Motor Driver Packs can operate one, two, three, or four axes of motion, and many other mechanical operations. Precision Cutters were available from machinery manufacturers in single, double, and triple-stepper motor drive models. In this application, the motors were operated by a single Bipolar Step Motor Driver Pack. Due to the control flexibility, the double and triple stepper motor drives models simultaneously processed a single part on one axis, identical parts on all axes, or different parts on each axis. They were capable of handling hard and soft extrusions, in a number of lengths; up to 1 in. in diameter. The selected unit cut steel and other metals, simply by switching the blade on the cutter mechanisim.

A small, automated punch press known as the Chassis Maker, offered many of the same features found in larger high-production machines. However it was substantially more cost-effective because of its design using the Anaheim Automation stepper motor and bipolar step motor driver and controller. It truly offered servo motor performance at a stepping motor price, by using closed-loop motion control. Anaheim Automation, along with Functional Robotics, developed the automated punch press for producers of precision electronic enclosures, brackets, and other sheet metal applications. Not only did the Chassis Maker provide complete precision and automated operation for bipolar step motor driver and controller products, it offered features such as a rotating clamp that turns the sheet metal 180 degrees, and clamp repositioning that extends the work area to 48 by 60 inches. The Chassis Maker can tolerate up to 12 gauge mild steel and 0.150 inch thick aluminum due to its 12 tons of punching force. The machine is only 80 inches long by 60 inches wide by 70 inches high, ran on 110 VAC, and requires 120 psi from an external air compressor. Anaheim Automations step motor controller board and high-performance bipolar step motor driver managed stepper motors on three axes: X and Y for the work piece, and rotation of the sixteen station turret. A PC computer deals with position verification and auto correction, and each axis is provided with encoder feedback. The PC uses software that uses punch commands in either English or metric units and includes capabilities for nibbling lines and arcs, handling line at angle functions, and punching grid, bolt hole circle, and user-defined patterns with micro jointing. In addition, the software provides for jobs that necessitate more than 16 tools and includes graphics for previewing parts before punching.

Anaheim Automation bipolar stepper motor Driver Packs are used in several radiation laboratories throughout the Unites States. These Bipolar Step Motor Driver Packs are packaged bipolar step motor driver(s) containing matched power supplies that are used in radiation laboratories to operate stepper motors. These centers, run by the US Department of Energy, conduct major experiments; one of which is in a two mile long linear electron accelerator. The major use of this accelerator involves moving high energy electrons from the accelerator to a positron electron asymmetric ring. This ring is approximately 230 feet in diameter and contains magnets that keep the electrons traveling at a high speed, close to the speed of light. As a result, radiation is produced. This radiation has broad spectral range, high intensity, small source size, high stability, high polarization, pulsed time structure, and a high vacuum environment. The type of radiation produced by the accelerator makes the ring an incredibly efficient way to conduct experiments. This particular facility is well-known and has attracted a myriad of people from all over the world to use the synchrotron radiation instrument for different fields of biology, chemistry, and physics. This facility has conducted experiments with more than 1,000 researchers who have traveled from hundreds of different locations in the USA, and many foreign countries. Nearby companies also use Anaheim Automations motion control products in the radiation lab for research. As detectors gather data, the storage ring emits X-ray beams toward samples of experimental semiconductor materials. This procedure provides detailed information about materials, including its atomic structure. During one experiment, seven two-axis bipolar step motor Driver Packs were also used in conjunction with detectors; because dual-axis, they operate stepper motors on 14 axes. These motors turn mirrors to position both the X-ray beam, as well as the sample. Typically, computers operate the stepper motor drivers and respond to the data from the detectors as the work progresses, and specify different movements that specialized programs run. The two-axis bipolar step motor Driver Pack saved the laboratory time and money, using matched bipolar step motor driver products, power supplies and fans, in a compact package. Hook-ups were a snap and error-free!

The obsolescence of L/R drivers in the inking system on a Large Hoe Directory Press made a large publishing company turn to Anaheim Automation for help, who provided them with high performance stepper Driver Packs and new motors. A primary part of the companys business entails printing telephone directories for major phone companies. The three story high Hoe press prints and folds the phone books in sets of pages. Each set generally consists of 72 pages, thus, in an eight hour shift, the press can turn out 240,000 sets of pages total. After printing, other machines in the plant collect, bind, and trim them. Extreme precision and rapid response time are necessities for machines that operate at such a high speed as the printing press. Lack thereof not only results in a loss of time, but money as well. Therefore when the original inking system began working inconsistently, the company found its costs getting out of control. The Hoe inking system consists of 24 pumps being driven by stepper motors to gain precision. Operators monitor the copy coming off the press and adjust the pump rate as required from a control panel. Quality could not be maintained due to the slow response times/inconsistent operations. Anaheim Automation helped design a new replacement system, which in order to avoid downtime, was installed on the weekend. The system consisted of 12 dual bipolar step motor Driver Packs, oscillator boards that provide clock signals and 24 new stepper motors for the pumps. The removal of the old L/R equipment left plenty of room for the bipolar step motor Driver Packs and oscillators. There was an immediate improvement in ink control once the press started up again, and the operators were able to quickly adapt to the machines new quick response.

Synchronizing sound and film has been a major challenge facing the entertainment industry, because most motors do not simultaneously start and stop. The problem was amplified with the increase in multi-projector presentations, such as rock shows, amusement parks, and stage shows. The introduction of bipolar step motor driver, motor and controller systems has made this task easier to execute. In many instances, Anaheim Automations stepper motion control products can drive several of the multi-image backgrounds you may see in motion pictures, a sound show, or perhaps in an amusement park. Before stepper motors, sometimes referred to as, stepping motors, motor stepper, and step motors, became available, only mediocre synchronization between sound and image could occur. The systems were expensive and unreliable, especially after they were in transit between events. Drastically different, stepper motors, along with a bipolar step motor driver, provided the ability to program a specific start, run, and stop speed, as well as the rate of speed. This gave the projectors the capacity to operate at different speeds for special applications. With bipolar step motor driver advances, not only are these speeds exact, but with an effortless input to the stepper motor controller system, they are easy and straightforward to change. Along with the customer, Anaheim Automation researched the requirements to drive the required functions, and produced custom bipolar stepper motor Driver Packs that could offer five times the flexibility of their previous systems, cutting their costs in half. With Anaheim Automations vast stepper motor, bipolar step motor driver, and stepper controller product lines, the customer also substantially reduced the bulk of controls and overall weight of their system. Even with improved performance, the projection systems were compact; they are small enough to travel within four road cases and they only take one person to set them up and operate them. These types of advanced stepper motor Driver Packs opened the door for many other opportunities in the filming and projection industry, not just projector synchronization. There is also great potential use for Anaheim Automations step motor, step motor controller and both unipolar stepper motor driver and bipolar step motor driver product lines in the areas of film editing, theater operation, special effects, and more.

The rotor, attached to a metal gear of the stepper motor is surrounded by electromagnets. The electromagnets also have gear-like teeth which face towards the gears on the rotor. The gear teeth of the rotor and the electromagnets do not come into contact with each other. Once the construction is understood, the motion of the stepper motor is primarily left up to the bipolar step motor driver. The bipolar step motor driver controls the motor by turning on the electromagnets individually through pulsed waveforms which travel through the coils to produce electromagnetic fields. This event causes the gears to line up with the first energized electromagnet, but not with the second. Therefore, to turn the stepper motor, the bipolar step motor driver turns off the first electromagnet and turns on the second electromagnet. This turns the motor one step. The continuation of this process, from electromagnet to electromagnet, allows the stepper motor to continuously rotate through the control of the bipolar step motor driver. Stepper motors can take 200 or less steps to make one full revolution. The direction of the motor rotation can be reversed by the bipolar step motor driver reversing the order of energized electromagnets.

The amount, speed, and direction of rotation of a stepper motor are determined by the appropriate configurations of digital control devices. Selecting the most compatible bipolar step motor driver, motor, and/or controller, can save the user money and be a less cumbersome motion control solution. Anaheim Automation categorizes the major types of digital control devices as follows: • Bipolar Step Motor Driver – offered in full-step, half-step and micro-step • Stepper Motor Controllers (sometimes referred to as Control Links – controllers indexers, and pulse generators sold separately or in drivers packs • Stepper Motor Driver Packs – packaged units that include drivers and optional controller, with a matched power supply (most models are enclosed units that are fan-cooled) • Integrated Bipolar Step Motor Driver/Controllers – packaged at the end of a stepper motor are drivers and simple controllers (only available for high-torque stepper motors) A bipolar step motor driver provides a method to precisely control speed and positioning. With each pulse converted into digital information, the motor is able to undergo an exact incremental rotation without the need for feedback mechanisms i.e. tachometers or encoders. With an open-loop system, the problems of feedback loop phase shift and resultant instability, common with servo drives, are eliminated. Before a designer selects a suitable bipolar step motor driver and motor combination for an application, there are certain variables needed to be considered. A designer must examine several parameters such as load characteristics, performance requirements, and mechanical design including coupling techniques for an optimal solution for a bipolar step motor driver and motor combination. Failure to do so may result in poor system performance or cost more than necessary. For optimum bipolar step motor driver motion control, the following factors should be taken into consideration: 1. Parameters: a. Distance to be traversed b. Maximum time allowed for a traverse c. Desired detent (static) accuracy d. Desired dynamic accuracy (overshoot) e. Time allowed for dynamic accuracy to return to static accuracy specification (settling time) f. Required step resolution (combination of step size, gearing, and mechanical design) g. System friction: All mechanical systems exhibit some frictional force. When sizing the motor, remember that the most must provide enough torque to overcome any system friction. A small amount of friction is desired since it can reduce settling time and improve performance h. System inertia: An object’s inertia is a measure of its resistance to changes in velocity. The larger the inertial load, the longer it takes a motor to accelerate or decelerate the load. The speed at which the motor rotates is independent of inertia. For rotary motion, inertia is proportional to the mass of the object being moved times the square of its distance from the axis of rotation i. Speed/Torque characteristics of the motor: Torque is the rotational (in ounce-inches) defined as a linear force (ounces) multiplied by a radius (inches). When selecting a bipolar step motor driver and motor, the capacity of the motor must exceed the overall requirements of the load. The torque any motor can provide varies with its speed. Individual speed/torque curves should be consulted by the designed for each application j. Torque-to-Inertia Ratio: This value is defined as a motor’s rated torque divided by the rotor’s inertia. This ration (measurement) determines how quickly a motor can accelerate and decelerate its own mass. Motors with similar torque ratings can have different torque-to-inertia ratios as a result of varying construction k. Torque margin: Whenever possible, a bipolar step motor driver which can provide more torque than is necessary should be specified. This torque margin allows for mechanical wear, lubricant hardening, and other unexpected friction. Resonance effects can cause the motor’s torque to be slightly lower at some speeds. Selecting a bipolar step motor driver and motor system that provides at least 50% margin above the minimum required torque is ideal. More than 100% may prove too costly 2. Calculation: Measurement of inertia, friction and workloads reflected to motor. a. In an open-loop stepper motor drive system, the motor does not “know” if excessive inertia or friction has made the motor lose or gain one or more steps, thus affecting the position accuracy b. Load inertia should be restricted to no more than four times motor rotor inertia for high performance (relatively fast) systems. A low performance system can deliver step accuracy with very high inertia loads, sometimes up to ten times rotor inertia. System friction may enhance performance with high inertia loads Experimentation: Tailoring Experimentation for motor sizing is critical due to dynamic changes in system friction and inertia, (load anomalies) which are difficult to calculate. Motor resonance effects can also change when the motor is couple to its load