Hi Mick,
I used a 6 wire stepper motor from an old dot matrix printer.
I bought this stepper motor driver circuit from Oatley Electronics:
http://secure.oatleyelectronics.com/...6e682531781194
(K142D because I have a 6 wire motor)
I then cobbled together a basic timing circuit using a 555 timer chip to provide the timing pulses for the driver circuit. I use my benchtop power supply to provide the power.
Here are some photos:
Pic 1 shows the stepper motor mounted on the tracker. It is glued to the threaded rod and the two pieces of wood on either side prevent the motor from spinning.
Pic 2 shows the circuitry. The driver circuit is in the grey box. My timer circuit is on the breadboard. The power supply is in the background.
Pic 3 shows the connector (generic 9 pin serial connector) used to connect the stepper to the driver circuit.
I plan to put the timer circuit on its own board and mount it inside the box with the driver circuit, then it is all contained in one box. I have been planning to do this for 6 months now but I haven't got around to it yet.
It works really well. My only concern is that the motor draws a lot of current. I wind the voltage down to 4 V to keep the current at about 0.8 A then the motor only gets slightly hot instead of very hot.
I think I need to add a current limiting circuit which I will also get around to one day.