Hello,

The following pages might give you some better ideas for the H-bridge:
http://www.dprg.org/tutorials/1998-04a/
http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html

Bertus

 

Hello,

The following pages might give you some better ideas for the H-bridge:
http://www.dprg.org/tutorials/1998-04a/
http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html

Bertus

Thank you. I did the dprg one. The voltage at input A when A,D are on high is 8.08V. B, C, D are between 1.5~1.6V.
When B,C are on high A is still 8.08V max, B max is 4.56, C and D between 1.5~1.6V.

 

The input voltages for the circuit you are describing, must be very close to 12v and very close to 0v for the circuit to work.

 

Thank you. I did the dprg one. The voltage at input A when A,D are on high is 8.08V. B, C, D are between 1.5~1.6V.
When B,C are on high A is still 8.08V max, B max is 4.56, C and D between 1.5~1.6V.

Did you add base resistors to the circuit?

 

You are entirely wrong with your suggestion.
Changing the transistors produces "shoot-through" and you don't know the speed of the incoming signal. Sometimes you have to sacrifice some losses to prevent the bridge blowing up.
You need to ask a lot more questions before suggesting a solution.

Thanks (not really again) for your suggestion but I will continue to answer questions as I see fit and you can do the same.
Don't presume to know what I do or do not know.

 

Did you add base resistors to the circuit?

Yes, 1k Ohm. I'll see if there are any loose connections because there should ideally be variation between the AD, BC based on polarity. My code has it going one way for 1 second then another way for 1 second.

 

http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html

The big problem with this circuit is the use of Darlington transistors.
The collector-emitter voltage is at least 2v to 2.5v per transistor and this means you lose up to 5v from a 12v supply.
Not a good design.