I just received my dual VNH5019 from Pololu. It's mounted on an Arduino Uno and drives 2* 12V 29:1 Pololu motors. I have independent power supplies for Arduino and shield (1x 9V battery for the Uno and 8x NiMH AA for shield).
I installed the library and all. When I run the Demo, only the motor connected to M2 is working. M1 motor doesn't do anything. No sound, leds on M1 screw terminals don't light up.
If I reverse the two motors then the other motor works, i.e. it's not a motor problem, both are working.
When I run the Demo code I don't get any faults, it simply says "M1 current = 0". M2 current looks OK.
When I run the Demo with motors disconnected, then LEDs of both M1 and M2 light up properly. I checked the voltage on the screw terminals using a multimeter. M2 look good (+11V and -11V, matching the command PWM). However M1 voltages are only +3.2 to -3.2V. They follow the PWM properly but only go +-3.2V instead of +-11V.
I don't know where the low voltage on M1 comes from. I'd appreciate any help, thanks!
You are in the position of having a known working and know failing circuit to compare.
So you should proceed by seeing whether any of the control pins for the two channels
disagree - that would be a clue as to where the problem is.
If all the control inputs to the driver board match between channels that suggests a problem
with the board (you've already swapped motors so the issue isn't there). So out with the
multimeter and check each pin (perhaps write a test sketch that drives both channels the same)
Its always worth a close visual inspection for shorts or "dry" solder joints or other
manufacturing defects too - again there are two channels to compare so things are
made easy.
I checked all pins with the multimeter for shorts and/or continuity. I found that Pin 9 had continuity on the Arduino only, and on the shield only, but no continuity when the shield was plugged on the arduino (ie, from underneath the arduino to the header on top of the shield).
I resoldered the "bar" of headers and now I get proper pin continuity on all pins, and both motors work (correct tension on M1 and M2 terminals).
I also found that if I push the shield to the max on top of the Arduino (headers all the way) the connection is actually worse than if I pull back a bit (like 2mm). Strange, but hey, it works.
Thanks for posting. I had exactly the same problem and couldn't figure it out. After reading this post I ended up re-soldering the points. That fixed the problem. Thought I'd post this to help others with the same problem.
