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# Driving a step motor (All you EE fans)

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4 replies to this topic

### #1outRider  Members   -  Reputation: 852

Posted 22 November 2005 - 05:11 PM

I'm trying to drive a step motor, using this chip, but I'm a poor EE and would appreciate a little help. As I understand it, the motor steps on each posedge of clk (this particular motor I'm using is 0.9deg/step), but I'm not quite sure how to drive the circuit from an FPGA or a microcontroller (specifically a M68K). The FPGA outputs vcc at 5v dc and 3.3v dc, and the 68K board I'm not quite sure, but I'm guessing in the 5v range. Can someone give me some pointers? Much appreciated.

### #2Mastaba  Members   -  Reputation: 757

Posted 22 November 2005 - 08:04 PM

Well, I would probably use Figure 11 of the spec sheet as a starting point. Just route some bits of one port to the motor driver inputs, and route the phase A output to some other port (or if you like to the same port as above).

### #3etothex  Members   -  Reputation: 728

Posted 22 November 2005 - 11:23 PM

It is fairly easy to generate a clock pulse from the FPGA. You just need a truncated counter (a counter that only counts up to the value you give it, say A, so it counts 0, 1, ..., A-1, A)

Then, check the output of the counter for the 0 condition (all bits are zero), and if so, output a 1, otherwise, output 0 (NOR logic)

Voila, you have a signal that pulses (positive edge) every A*(fpga clock period) seconds.

Also, make sure you feed the correct voltage ito the stepper driver :)

EDIT: I guess I assumed you needed something that would move the motor at a given speed. If this isn't what you wanted, post some more details.

### #4python_regious  Members   -  Reputation: 929

Posted 23 November 2005 - 12:45 AM

You use an output of your microcontroller as a clock for the motor. The higher the frequency of that output, the faster your motor would be. You'll probably need to step down the voltage, and you will need to use a power amplifier stage (you can get a darlington pair of power transistors in one package, which would be suitable) before the motor.

Edit: Just read that data sheet... Seems a little pointless to me, since it doesn't really take much to just do it yourself. It says you can connect that straight to a stepper motor, but since it can only supply 350mA, you're only going to be able to use a very small motor, or you just won't get any torque.
If at first you don't succeed, redefine success.

### #5ROBERTREAD1  Members   -  Reputation: 100

Posted 23 November 2005 - 01:54 AM

http://www.ar.com.au/~softmark/page44.html

http://www.standa.lt/products/catalog/motorised_positioners?item=175&prod=microstep_driver_usb_interface

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