Hardware Peripheral Input/Output

Stepper Motor Drivers

A "stepper motor driver" is a board with some big transistors that turns the wimpy "step" pulses from a parallel port (or a microcontroller) into the high-voltage, high-power, sequence of coil energy sources for the wires of a stepper motor.

• NEW! Roman Black's Linistepper 2. stepper controller kit Drives medium to small unipolar (5, 6 or 8 wire) stepper motors with ultra smooth microstepping modes. Proceeds support our site.
• NEW! Roman Black's SLAm stepper controller kit Drives medium unipolar (5, 6 or 8 wire) stepper motors with microstepping. Proceeds support our site.
• Design of a High Current Bipolar Stepper Motor Driver drives bipolar (4-wire) stepper motors.
• AVR-Based Microstepping Bipolar Chopper Stepper Motor Driver (STMD) http://avrstmd.com/ , as the name suggests, drives bipolar stepper motors. $65.

Stepper Motors

Also: Estimating Needed Size, Determining Wiring and Connection Options, Torque: Measuring and Torque Units Conversions

A stepper motor is a kind of electric motor with an internal rotor containing permanent magnets and a set of electro-magnet coils around the rotor which are switched electronically. Stepper motors "cog" to a limited number of positions, but with a microstepping controller, which partially activate ajacent coils so that the rotor rests between positions, stepper motors can rotate more smoothly.

Advantages: The primary advantages of stepper motors are that since they will move only as the controller changes the coil that is energized, the position of the motor can be known without any external feedback. Although it is possible for the motor to be turned out of phase with the coil exitation, which is know as skipping or missing steps, in most cases the reduced cost of the system is justified. Stepper motors are "brushless" unlike most other motors and so generate less EMI.

Disadvantages include lower power effeciency, higher cost per unit, and the need for a more complex drive circuit aka controller.

Control Signals: The stepper motor controller typically accepts two inputs from an external source: Step and Direction. The Direction signal set the direction of rotation and each pulse on the Step signal causes the controller to move the motor one step in that direction. The controller translates these signals into different patterns of current flow in the coils, which result in the movent of the motor.

Size: Type 23, NEMA 23 or any other like that refers to the mounting arrangement only (mounting hole pattern and size, diameter of shaft)

Application: Stepper motors excel at driving loads needing up to about 100 Watts of power to move at less than a few hundred RPM with accuracy of 1/200th of a revolution. Lighter loads can be driven faster or with more accuracy.

Estimating Stepper Motor Size:

With Java script

CoAMarcus^ says:

"Pick the weight of the heaviest item you are pushing around. If it weighs 40lbs, use 40lbs. multiply it by the IPM [Inches Per Miniute] you want. Say that's 1,000 IPM. Divide the result by the magic number "531". The answer is 75.3 Watts".

Watts = IPM * Lbs / 531

or

Watts = torque in in-oz * RPM / 1351

Stepper motors are commonly used to convert milling machines to CNC control.

Also:

• Wiring for information on the different types of wiring inside a stepper motor and finding which wire is which.
• Connection Options explores the different ways a stepper motor can be connected to a stepper driver and the advantages and disadvantages of each. +
• Torque: The torque required to move a load is dynamic or detent torque. Don't be mislead by a rating of holding torque. A typical stepper motor / drive system will lose almost half of its holding torque when moving at low speeds and will have no torque at all at some higher speed. Look for the torque curve.
  • Units Conversion
  • Measuring
• Floppy Motor Steppers
• Decoding Quadrature Encoders with a PIC
• Ubicom SX stepper motor controls
• PIC Microcontroller stepper motor controls
• Using Stepper Motors as Encoders
• Comming soon: QuickStep

See also:

• http://www.cnczone.com/forums/showthread.php?t=52090 Geckodrive FAQ: General, Steppers, and Servo Questions Answered
• http://www.codeproject.com/vbscript/Stepper_Motor_Control.asp Stepper Motor Control through Parallel Port from a Visual Basic script in MS Excel
• http://linuxgazette.net/122/sreejith.html Liniux stepper motor tutorial
• /techref/member/FL-gmail-A53/index.htm 2 stepper motor driver+
• @spam@aaron.groups-Remove- at -Remove-gmail.com refers to

  http://www.bright.net/~agarb/STMD/STMD.html For those that are interested, I've been working on an open-source bipolar, microstepping chopper stepper drive. Schmatics are available and it is my intention to also make the source code availabe once I get it cleaned up.

• http://www.cs.uiowa.edu/~jones/step Nice tutorial on steppers
• http://www.doc.ic.ac.uk/~ih/doc/stepper/ Nice tutorial on steppers
• http://www.beowulf.demon.co.uk/serial-stepper.html
• http://www.allegromicro.com Has some nice stepper motor controllers with logic, protection, drivers, etc... all built in.
• http://www.njr.co.jp/e05/ee.htm excellent app notes with full theory but also practical applications.
• http://web.archive.org/web/19990218185922/http://www.sig-positec.co.uk/bmotors.htm info on different types, etc... pictures missing.
• http://www.galilmc.com/support/motorsizer/index.html You put in system type, load mass, etc... and it tells you want motor and drivers to use. Does require registration.
• http://www.nookindustries.com/acme/acmeglossary.cfm Everything you want to know about leadscrews
• http://www.microchip.com/Microchip.webcontent.provider/Video.aspx?id=en548368 "Stepper Motor Control with dsPIC DSCs." Really good "Webinar" video explaining the issues encountered in stepper motor drive, especially bi-polar drivers. Despite the title, most of the information is /not/ specific to dsPICs.

Roman Black says:

http://romanblack.com/stepper.htm   "I have built a test rig to measure both holding torque and shaft angle with high accuracy. This will let me measure (tune) motors for microstepping, to get exact torque and angle for every microstep.

If anyone is interested I have done the measurement on a 5.1v 1A/phase bipolar 23-frame motor, it was WAY off the mathematic values that many microstepping drivers run at. Now I can tune my new CNC driver for perfect performance. Note that this motor is very similar to many common "surplus" steppers that we all use for projects"

Questions:

See:

• /techref/piclist/cump/hardware.htm CUMP hardware+

Comments:

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