Hi guys. This is my first posting to this forum and I apologize if this is not a suitable place to ask my question.
I am building a simple 2-axis plotter based around the components extracted from a craft-robo cutter. The hardware is complete and now I am half way through building the stepper controller to drive it all.
As the local electronics store here doesn't supply any bipolar stepper driver chips I decided it would be fun just to do it all using power transistors so I built an h-bridge that runs on 24 volts using TIP31C and TIP32C transistors.
I just sort of hacked my way through that and it seems to work great. Drives a stepper coil backwards and forwards no problem.
However I am up to the last part of the h-bridge which is the interface to the parallel port and I have run in to one snag and I do believe it is in my choice of optocouplers.
I picked triac ones and I can now see this was a mistake as the MOC3020 series turn on but not off!
I understand now that these were not really designed to run off a parallel port but for AC applications.
But I figure I got this far and the rest of the board looks good so one more little hack might just do the trick for me.
Anyway my question was if any trick exists to turn these opto couplers on/off via a parallel port.
I was thinking perhaps by putting a cap across the led side to force them to pulse?
As you may have gathered I am not an electronics Guru.
I just cobbled this together and am happy I got this far!