H-Bridge

I am designing a H-Bridge to control my DC motor so it can turn in both side.
It is going to control by using micro controller PIC16F877A.

The control(output) signal from PIC will turn on the NPN Transistor BC549 to charge the coil in relay.

I program it so that every 5 second the motor will change it turning side but sometime when it change it stage, it will affect my circuit and reseting my program...

I wonder is it because of back emf from the motor.. I try to add diode 1N4007 or higher value of resistor at the base of my transistor but this doesn't solve the problem....

help....

try to add diode between the collector and emitter.

DO you have adequate capacitor bypassing on the power supply rails of the PIC?

I would add localised bypassing caps on the H-Bridge. Putting a cap across each motor would also help.

Thx for all ur advice, I will try it ASAP...

The method of placing capacitor beside motor really works!!
But... when I connect it to a gear... the same problem happened. I wonder is it because of the current required is too high...
Any suggestion?? Increasing the capacitance value will do??

Engeocer said:

The method of placing capacitor beside motor really works!!
But... when I connect it to a gear... the same problem happened. I wonder is it because of the current required is too high...
Any suggestion?? Increasing the capacitance value will do??

Click to expand...

Check that the voltage to PIC supply is not being pulled low when the motor draws a heavy current.

Lets know.