one side of robot not running - and need general electronics troubleshooting advice

[alb4h]

Hi all,

Thanks for the posts. I did read them yesterday at the shop when troubleshooting this problem.

The problem was a bad ribbon cable. We swapped it out with a DB37 cable and that resolved the initial problem.

I was unclear when I initially posted about switching the two sides. We switched position at the DS, which would indicate a problem upstream of the PWM cables.

So the new cable resolved the initial problem, then we had a new problem to consider.

Once we got both sides running, we noticed a difference in speed between the two sides. Originally I thought that it was due to motor or gear box differences but decided to switch the PWM cables again (at the DS), to see if that effected anything. And I was a bit surprised to see that it did!

Originally side A was running faster than side B. When we unplugged side A from pin 1 on the DS and side B from pin 2, and plugged side A into pin 2 and B into pin 1, then side B ran faster than side A. It's as if Pin 1 is outputting a greater signal than Pin 2. What would cause this??? Again, all lights on the DS are bright, including the light for the robot indicator light.

We are just using the default code for C++ on this bot. The programmers are using a different test bed right now.

In either case, when driving the bot it was easy enough to compensate for the difference, but we'll be adding encoders next and will have to implement some feedback to get it to drive straight during autonomous.

AGain, thanks very much for taking time to respond. I appreciate it.

Ann