Power amplifiers?

Question

Hi, I used two 2N3055 power amplifiers darlington connected to amplify microcontroller output to control a 24v dc motor. PWM works fine and I have complete control over the motor's speed.

Now I face the problem which needsme to reverse the motor. I am not sure how to do that. What ever solution I stumble upon leads to a situation where one way or the other the supplies get shorted out.

It would be really helpful if any one gives an Idea of how to reverse the motor.

Thanks.

Answer 1

yes, the supplies could get shorted out, but a few diodes in the right place will protect that.

So a DPDT relay will do that, or you could do it with transistors. Difficult to do with words only... Draw a schematic with power transistors, 2 PNP, 2 NPN and diodes.

I try to find an online schematic to match...

.

Answer 2

well not sure of the complete circuit you have but what about just using a double pole double throw relay (DPDT). Tie the output (the commons) of the relay to the motor itself. Them tie one pair of the relay contacts to + and -, and the other set to - and +, thus creating a reverse polarity effect. Then all you would need to do is trigger the relay. This would prevent the reversing issue you spoke of and isolate the two sets of contacts. Since it's a DPDT, you'll never have it forward or reverse at the same time... Will this work for you

Answer 3

You will probably need an H-Bridge circuit. This will allow you to switch between forward and reverse. If you have a spare microcontroller output, you can use it to control the H-bridge. Good luck!