Motor stutters as it spins

Other Hardware Motors, Mechanics, Power and CNC
1

Hello,

I built and prototyped a motor controller using an L6205 chip and an Arduino on a breadboard with no problems, but when I moved the same setup over to a prototyping board (similar to this - http://www.futurlec.com/Pictures/STPBRD2.jpg), but when I power it, the motor just stutters. The code I'm running is to switch the motor direction every 5 seconds (but it doesn't even work properly if I just let it run in 1 direction). I'm powering the circuit using a 12V output power supply from the wall. The power supply should have more than enough capacity for this (I used this on the breadboard previously with no problems). Connecting the motor to a battery directly definitely works.

This is what the circuit should look like (I also added two sense resistors rather than leaving that part shorted):

This is what I had before:

and this is what I have now:

1024×768 106 KB

I'm not sure if I've provided enough info, but any help would be appreciated..

2

HMM Never mind...

I forgot to connect my circuit ground to the arduino ground...it works now.

3

Ah, that was what I was going to suggest from looking at the pics...