EAS Electronics

EAS MicrostepPLD is our 2 axis microstepping chopper driver board for stepper motors. It is based on the National Semiconductor LMD18245 3amp 55volt full bridge motor driver.


MicrostepPLD manual (.pdf), schematic (.pdf), layout (.pdf) and parts list (.pdf).
MicrostepPLD silkscreen layout by part number (.pdf)
Digikey order part list for the MicrostepPLD.


Note: on some of the Digikey parts such as resistors and capacitors they require a minimum qty order of  5.

Just change the quantity to 5 and then add list to order.

Xilinx CPLD based.
2 axis driver on one single board.
Supports half/full steps plus 4,5,6,8,10, or 16* microstep modes. Only one stepper mode can be programmed into the CPLD at one time, please state which version required when ordering.
Drives 4,6 or 8 wire bipolar/unipolar stepper motors up to 3amps at 55volts per phase.
Adjustable chopper current drive, no large external resisters required for stepper motor current limiting.
Standard TTL step, direction and enable inputs.
Capable of over 100Khz step pulse input rate.
The LMD18245 driver has internal overcurrent and thermal shutdown protection.
Heat sinking required.
Professional quality board with silkscreen.

Also available is a parallel port Stepper Breakout, or our latest optical isolation board.Opto Breakout.

* Using standard 1.8 degree 200 step/rev motors,
16 microstep = 3200 steps/rev
10 microstep = 2000 steps/rev
8 microstep = 1600 steps/rev
6 microstep = 1200 steps/rev
5 microstep = 1000 steps/rev
4 microstep = 800 steps/rev
half step = 400 steps/rev
full step = 200 steps/rev

Using higher microstep rates will decrease the chance of motor resonance affecting performance. Resonance can sometimes cause a stepper motor to stall at a particular step frequency rate. We recommend the 8 microstep version for most applications.

Please note that 16 microstep mode requires a fast input step pulse rate to achieve high motor rpm speeds. We do not recommend the use of a full or half step drive due to the likelihood of motor resonance. It is only available for those who require it for a specific application.

At least 900rpm using a modern Pacific Scientific P21NSXC 116oz Nema 23 bipolar stepper motor. Stepper motor voltage set to 36volts, using 8 microstep mode. Computer hardware is a Windows XP PII-400Mhz running a demo version of MACH2 cnc software. The maximum motor rpm was step rate limited by the PC. This computer was only able to output approximately 24000 steps/sec. Higher rpm can be achieved by increasing motor voltage to the maximum of 55volts and using a faster computer that can output higher step rates.

We recently tested a old Superior Electric M091-FD09 150oz Nema 34 stepper and achieved over 1500rpm using TurboCNC on a old pentium200 PC. Stepper motor voltage set to 36volts, using 5 microstep mode and half winding hookup to driver. TurboCNC is able to output an exceptionally smooth pulse train; this maximizes the stepper motor performance and speed.

Some stepper motors may only run 200-400 rpm due to high winding inductance and magnet/rotor design. Modern lower voltage stepper motors achieve much higher rpm speeds and should be used if high speed is required in your application.

3.8" x 2".

Power requirements:
Requires external 12-55volt DC motor supply.

Works great with standard 24volt AC transformers. This is approximately 35volts DC after diodes and filtering caps are added to complete the power supply. We recommend using a unregulated linear power supply and not a switching type supply.

We have tested the LMD18245 driver chips continuously with a 44volt power supply. Although the driver chip can handle 55volts, there should be some safety margin for stepper motor induced back EMF voltage. We recommend no more than a 44volt supply for reliable and trouble free operation.

Bare PC Board with one preprogrammed CPLD: $20.00
Extra preprogrammed CPLD: $10.00, only needed if you want to use a different step rate.
Please state which stepper mode you require- full step, half step or 4,5,6,8,10, or 16 microstep version. Only one version can be programmed into the CPLD at one time. We recommend the 8 microstep version and will ship this version if you do not state your preference.

Not all stepper motors are able to resolve 16 microstep resolution. Most modern stepper motors should work fine though.

Please contact us for custom microstep modes, we may be able to design and program a CPLD for your exact needs. We also have a version that can drive two steppers from a single step/direction input. This is useful for larger machines that use dual lead screws per axis.

For Astronomy users, MicrostepPLD can be used to control your telescopes azimuth and altitude stepper motors using 10 or 16 microsteps for smoother movement.

We will not be releasing the Xilinx ISE design files or CPLD programming device files for this stepper driver board. If you desire a open design/source stepper driver, please check out our Microstep driver.

No assembled units or parts kit are available. Bare PC boards are in stock.

Please include $5 shipping and handling for destinations within the continental United States. All other areas, please contact us for shipping charges.

For those only interested in purchasing a single bare pcb board, shipping and handling can be avoided by sending us the cost of the pcb and include a self addressed stamped envelope with your order. Please attach three first class stamps to the envelope with your legible return address. We suggest using cardboard floppy disks envelopes that can be purchased at office supply stores. US only.

Stepper motor test video. Two Vexta Nema23 stepper motors driven by MicrostepPLD Driver with 44volt power supply, 8 microstep mode. Computer is a P2-400 running TurboCNC. Stepper motor is spinning at a maximum rate of 1900RPM. This is the fastest step rate this computer parallel port can output steps, approximately 50,000 steps/sec. Higher step rates is possible by using a faster computer.

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