Hello
i am new to electronics and i started working on a mosfet h bridge circuit but it doesnt work as intended
when i switch on the switches on the gates of Q2 and Q3 the motor rotates just fine but when i switch on Q1 and Q4 it does rotate backwards but very slow compared to the forward rotation speed and i wonder why is that ?
here is the H-Bridge Design
thanks in advance

 

One mod is to adds a 10K resistor from base to emitter on Q5 and Q6. It is never a good idea to leave inputs at non defined levels. You may get away with it but you may not too.
What power levels are you trying to control?
There a quite a lot of ready made H-bridge chips around. And I would recommend at least using a H-bridge FET driver as it will take care of shoot through protection and some do over current protection too.

 

One mod is to adds a 10K resistor from base to emitter on Q5 and Q6. It is never a good idea to leave inputs at non defined levels. You may get away with it but you may not too.
What power levels are you trying to control?
There a quite a lot of ready made H-bridge chips around. And I would recommend at least using a H-bridge FET driver as it will take care of shoot through protection and some do over current protection too.

Thanks for the reply i am using Arduino uno to control the motor we had the idea of using the chip but we decided that it is better if use this chance to learn how make an H-bridge

 

Thanks for the reply i am using Arduino uno to control the motor we had the idea of using the chip but we decided that it is better if use this chance to learn how make an H-bridge

On your schematic you are missing the pull-up resistor between the gate of Q3 and the positive supply (should be the same as Q4). Without that resistor, a charge will remain on the gate of Q3 and it will not completely turn off.

 

On your schematic you are missing the pull-up resistor between the gate of Q3 and the positive supply (should be the same as Q4). Without that resistor, a charge will remain on the gate of Q3 and it will not completely turn off.

Duh! I completely missed the lack of a pullup. And that could well cause the problem of non symmetrical speed.

 

Duh! I completely missed the lack of a pullup. And that could well cause the problem of non symmetrical speed.

It certainly can. I hope it works for you.

 

thank you all for your help