Posted by Nick Atkinson at 14:57 on 2011 Jul 20
Michael Covington had a circuit in his book on Astro Photography. I did construct this buying the chip from Dontronics in Australia for Circa £4. This produced a square wave form that was capable of driving a £240 volt syncronous motor. For the dec control you need a reversible DC motor. I modified the circuit with a half bridge driver and constructed a push button controller. You do need to have some experiance in soldering circuits.