Hello all,

Im new to this site and have many questions

I am currently in the process of cunstructing a 2'x4' cnc router and would like to know how to control the dc motors (which have a 'stepper feel' when the shaft is rotated) with the fpga. My expirence with fpga's is beginner college it just that I cannot think of an accurate logic circuit to control the motor.

The fpga has to control the axis step, axis direction, and axis enable from the kellyware cam software to the forward, reverse, and enable lines from the schematic on http://www.mcmanis.com/chuck/Robotics/tutorial/h-bridge/bjt-circuit.html


list of parts:
flex fpga
assorted semiconductors
24v dc geared down brush motors (13150 rpm, 2.18a) out of a letter stuffing machine with 10 segment optic wheels
computer
kellyware cam software

Thanks for your time,
Dan

With an FPGA you are on your own. You have to assign pins, declare which variables are registered and which not and define the logic. I can even throw some code in, which is Lattice-Chinese and it would'nt help you any further.

Coil1_L= ServoControl & !Direction;
Coil1_R= ServoControl & Direction;

Coil1_LLo = !Coil1_R & Coil1_L & !Delay & Puls;
Coil1_LHi = Coil1_R & !Delay;
Coil1_RLo = !Coil1_L & Coil1_R & !Delay & Puls;
Coil1_RHi = Coil1_L & !Delay;

This is the core definition for a H-Bridge, switching the appropriate coils according to puls and direction, with a delay for change of direction, derived from last direction = not direction now. I think this is as far as you can get help

Carel

I dont want to be a nag but is there a website that I could replicate and/or hack a similar logic schematic from, using (gates, flip flops etc...).

Thanks again,
Dan

You can post the question to one of the FPGA newsgroups. Nobody will be very helpfull to someone who wants to jump quickly over the problems. This is homework?

Carel