For the output pins I used a Darlington array chip to drive four relays. The darlington comes in an 18 pin DIP - it has one input at 0v (common), one input at relay voltage, 8 inputs from the computer (which you can double up if you want) and 8 outputs which ground the relays. (you can double these up as well) Each pin can control 0.5 amps. It is very easy to use and can be driven directly from the printer port.

I hope you resolve your problem.

Jim

Jim,

That darlington array chip sounds alot easier than the circuit I used. Do you have a part number for it I could look up please?

Thanks
Simon

I don't know which country you are in.  Mine are from Maplin in the UK.

Part No  ULN 2003A (7 pairs) or ULN 2801A (8 pairs). They are not the ones I use, which are older and now out of production, but these are the present equivelant.

Jim.

Jim,

I am in Basingstoke. UK.

Thanks for the part numbers, I will be off to Maplin just as soon as they open again!

Thanks again
Simon