Tranny-based H-bridge

Hi guys,

I know I can easily use a H-bridge chip these days but I want to just play a bit with the old trannies I have lying around.

I've constructed the main part of a H-bridge as follows:



I'm quite sure turning on Q4 means with respect to GND as per the circuit, but is Q1 turned on with the same GND reference?

(PS Q1 and Q3 is TIP42C, Q2 and Q4 is TIP41C in my case)

I've added 2N2222 collector and emitter between the bases of Q1 and Q3 respectively to turn on a motor in one direction, by turning on the 2N2222 base with respect to GND and a resistor. It worked yesterday. Now it didn't. So I'm quite sure I might have wrongly understood the circuit.

Thanks.

Vizier87

Here's the H-Bridge from the Cybot robot magazine, have a look at that, I drew out the circuit and also explained how it worked.

Be aware though that's it's absolutely critical that you take care NOT to turn both sides on at once.

I didn't realize all these years you were part of the Cybot project! My brother used to buy the Real Robots magazine until we completed the Cybot (save the stickers issues).

Thanks. I'll try it soon.

Vizier87

I use this... It cannot short ( well I haven't managed to.)
.

I've driven quite big motors, and it lends itself to PWM control (Which is why i wanted it).

The information that Chuck McManis gives is not appreciated enough on the internet. He makes things simple enough for even dummies like me to understand.

It's a very good bridge setup... I used it for my toy crane... I had one ( before I crashed my company ) to simulate real time issues.. Stood about 2m high and I could do alsorts with it.. The bridges were driving the boom up and down and the hoist.. I had 1amp 24v motors.. Pretty good.

I'm gonna have to make another.. Remember the turntable for welding... Tada.... Works very well.