Ok heres a quick drawing of the circuit
Basically the unit is controlled by a 24v source which is shunted through a 7805 5v regulator for the 555 timer and driver logic. In theory the unit can run on anything between 12 and 24v easily as long as enough current is supplied via the power supply.
Once the 555 timer gets its power the dischaging capacitor and trimmer/supply resistor make up the timing for the clock signal that is fed to the input of the driver chip. The signal is fine tuned from 6hz to 133hz using the trimming resistor starting at 50% duty cycle. I can change this range using the capacitor and resistors. If you google 555 timers you will find many amazing things they can be used for
Once the clock is fed into the driver it has what it needs to step the motor however it requires a grounded ENABLE to conduct to the outputs. If ENABLE is grounded without a CLOCK signal the motor will lock and hold position. To reverse direction of normal operation the DRIVE connection is shorted to ground.
Full step / Half Step modes can be enabled by switching each to ground
Overall it is a very flexible driver capable of being run off a PC no worries as all it basically needs is a clock signal and a few other grounds.
I was lucky to have a dedicated driver for the motor as 3 Phase motors are a bit more difficult to use due to the windings needing either + - or open to function properly.