Interference in the circuit

[raitl]

I am making a new bot and using two geared DC motors. In my last bot I used steppers so I did not run into this kind of problems. But now my circuit is flooded with interference when the motors turn on. I actually killed a PIC mecause of that. So now I bought an oscilloscope just to sort this out. As I have never used an oscilloscope before, the instrument is still new to me.


Ok, so I have two ceramic capacitors, 100nF each, connected between each motors supply pins. And connecting the oscilloscope probe to the positive of the circuit, and the probe ground to the circuits ground, oscilloscope voltage range set to 20mV and Time/DIV to 1ms. The image I am seeing is this:

**broken link removed**

Now I have tried 220nF and 1uF capacitors across the leads, but the results are about the same. So how do I get rid of that motor noise in my circuit?

 

[be80be]

Do you have blocking diodes on your motors

 

[raitl]

Yes I do. This is my motor control board circuit:
There is an error on this schematic which I have corrected. I am now using pull-downs on all I/O lines.
**broken link removed**

 

[be80be]

Take a look at this site Reduce Motor Noise

 

[raitl]

Thanks a lot! I managed to get the interference down to 40mv now. Going to solder a new PIC into the circuit tonight and see how it will behave.

 

[be80be]

Put you socket in for your pic

 

[raitl]

The socket rises the PIC too high. Even though I have a low profile socket. It is a tight fit as it is