PICAXE unipolar stepper motor controller

8 March, 2008

Here’s my stepper motor controller, based on an 18 pin PICAXE microcontroller. The idea is that this chip takes away the processing overhead associated controlling a stepper. A master CPU (of some kind, potentially a PC) can send a serial command to the PICAXE telling it how much to move and at what speed (and direction). A Darlington driver array controls the power and a 7-segment display shows the current coil powering. Here’s the schematic (PICAXE programming connector not shown):

schematic

The way I’ve programmed this is different to other approaches I’ve seen. These tend to complete a full rotation every time. I’m sure others have done controllers that manage sub-rotation control like this but maybe not the way I’ve done it. I basically have a single value which defines how far the motor has rotated. I then increase this number step wise and use modulo division (//) to find out what position the rotor should have.

Program and video of operation after the break…

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