interface to the stepper motors

Here is a simple PIC based interface for stepper motors requiring more than one amp per phase.

The monitoring logic is compatible with CNC@net : a direction bit, a advance bit.

The solution that I implemented uses a microcontrolor (PIC 12C509 or 12C508) and 4 power-logic-mosfets.

I foreseen a PCB per motor located directly close to the motor which avoid conveying strong currents over lengths of wire and is more modular

Here is the electronic scheme :

Logic MOSFET are compatible with a 5V level and thus directly attacked by the output of thePIC (mine are IRLZ14 available at radiospare for less than 10 F each).

The diodes are fast switching diodes. I'm not sure they are needed, you can try without if you don't want to wire them !

The PIC must, of course, be programmed. You will find the code in file PAP.HEX for the 12C509 or PAP508a.HEX for the 12C508 family, the C source is available in PAP.C ...

Here on the scale 2x, establishment of the components, on one small PCB which you can download here (scale 2x) .

If your motors are 5V ones, you can connect the two PLUS (engine and PIC), a strap is foreseen for this purpose in the center of the circuit.

A slight improvement : add one zener diode !

This improvement has been proposed by JF Delhove. It worths doing it, torque and speed performances of your motors will be far better...

Just follow the electic scheme :

I did not draw a new PCB ; just a patch on the old one. Rather than long explanations, everything is here on the following drawing.The PCB is seen from the copper side.

The zener voltage is the same as the motor (eg : for a 12 V motor ==> a 12 V zener). Just choose a 1 W or more device.

translation of the post-it :

- suppress the 4 diodes connected to the ground,

- cut the copper as shown (pink on the drawing)

- weld the zener diode directly on the copper side (3 weldings are needed - in red on the drawing)

- don't forget to insulate the zener pin (yellow on the drawing)