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
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.
Specifications:
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 breakout board.
* 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.
Performance:
Atleast 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 a 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.
Dimensions:
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.
Price:
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.