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Finally got this working..
The main thing i had problems working out was the delay timing for each step. 34720 microseconds seems to be pretty spot on, going on 200 seconds per rotation of the motor. The motor does not like pulses lower than 6000 microseconds.
The GS-280 pulses are 8.3milliseconds long, however there is about a 50% idle time for some reason. So the controller pulses each pin on/off 6 times in 50ms, and then is idle for another 50ms. The value i worked out gives constant pulses. I doubt it will make a noticable difference though.
I used an Arduino Deumilanove, and a ULN2003 darlington array as a driver chip to switch the 12v. Its quite easy to construct. Jaycar sells all of the parts. The most expensive is the Arduino microcontroller - There are cheaper ways to do it, i am sure.
I have implemented a basic serial command set that allows modification of the delay, plus a simple rate change/rate reset and direction change. I interface to this with a simple python script to send the commands at the appropriate times. This allows me to perform drift aligns with an exposure length of my choosing, all fired off from the comfort of the big screen computer i can then use to examine the images to determine what sort of alignment is required. I only need to go outside to make the adjustments if required - No more crouching over a handset!
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