Motor Control H-bridge

**anita1984** · Dec1-09, 03:18 PM

I am building a H-bridge to control motor in forward mode and reverse mode , in the attachment i draw the schematic of the circuit , my problem is that the output signal looks like in the picture DSC07167 black signal and i need it like the red signal. How should the input signal of 2 PWM to have on the ouput the both mode? What do you recomand me. my inputs(before logic gates signals) are in the picture DSC07168
Thanks in advance,

**berkeman** · Dec1-09, 06:55 PM

Originally Posted by anita1984

I am building a H-bridge to control motor in forward mode and reverse mode , in the attachment i draw the schematic of the circuit , my problem is that the output signal looks like in the picture DSC07167 black signal and i need it like the red signal. How should the input signal of 2 PWM to have on the ouput the both mode? What do you recomand me. my inputs(before logic gates signals) are in the picture DSC07168
Thanks in advance,

Sorry, I'm not quite understanding the question. Your circuit looks okay for driving the H-bridge, assuming the logic drive signals are correct. Perhaps you could show us your truth table for the 4 logic inputs to the drive circuit?

**anita1984** · Dec2-09, 05:20 AM

Hello i am sending the logic table , i think i have problem with the input signals to the logic gates and the result isn't like my need
A and B are in input to the logic gates
Av and Bv are the output from thr logic gates

A B Av Bv
1 1 0 0
1 0 1 0
0 1 0 1
0 0 0 0

Thanks in advance

**Topher925** · Dec2-09, 11:20 AM

I'm assuming that the red signal has a negative voltage component. In that case your first going to need a negative voltage supply and your probably going to want to add the two signals using an op-amp, also commonly called an "adder".

**berkeman** · Dec2-09, 01:30 PM

Originally Posted by anita1984

Hello i am sending the logic table , i think i have problem with the input signals to the logic gates and the result isn't like my need
A and B are in input to the logic gates
Av and Bv are the output from thr logic gates

A B Av Bv
1 1 0 0
1 0 1 0
0 1 0 1
0 0 0 0

Thanks in advance

What are A, B, Av, Bv? I don't see them labelled in the schematic. And what is the output for each of those input combinations?