H-bridge problem
Uhh... Right. I've read your reply over a few times, gave it a +3 helpful, but you'll need to lay it out more clearly for me, I'm afraid.
The base voltage must be lower than the emitter for a PNP transistor. Right. What about 0 volts on the base and +12V on the emitter. Wouldn't that satisfy it? I.e. it conducts when it's input is low? ... But I can clearly see the problem about the PNPs. They won't reliably switch off when they're fed a mere 5 volts at the base, right? I should mention that my actual supply is 9 volts and my chip runs at 5Vs through a regulator, so the actual relation is 5:9. Got any suggestions on how to get this working? Maybe an additional set of NPNs going from the chip, driving the PNP bases in the H-bridge? I just need simple backwards and forwards switching here, with as few components as possible. 4 transistors for a single motor seems a bit much already. I have many 0V/5V outputs available on the chip that I can switch on and off.
I originally tried an arrangement where one pin switched on two NPNs, one had it's emitter to ground and collector to the motor's cold, the base connected to the chip and the other NPN. the other NPN was connected with it's collector to +9V and the emitter to the motor's hot, the base as described earlier. This didn't work, for some reason. One'd think so, the current passing out one transistor, into the motor, and out the other way, and to ground, but no...
The plan was to have two such pairs, wired opposite of each other, going to the motor, a sort of H bridge with only two inputs and NPNs only. I'm not sure what the flaw in that setup was yet...