If your robot is jumpy, has watchdog timeouts, loses connection to the field, etc.

[Randy Forgaard]

I just wanted to pass on a discovery we made about a problem with our robot, in case it helps some other team that is in the same boat, either this year (in off-season tournaments) or in a future year.

Twice this season (fortunately, not during a tournament match), our robot has suddenly developed a vexing problem where the driving is jumpy, the robot starts and stops, and there are watchdog timeouts (visible in the error display on the driver station). Very weird in both cases, because just minutes before, the robot was working great, with no change in software or wiring.

In both cases, we eventually discovered that the problem was an intermittent power connection on the robot. The first time, we found that one of the wires going to the robot's main breaker was getting loose, and making an intermittent connection. We fixed that, and the problem completely disappeared. We got lucky, and noticed a small spark at the main breaker that clued us in to the problem.

The second time, we discovered that the lug nut holding one of the wires to the battery had gotten loose, and the battery was making an intermittent connection. Swapping batteries fixed the problem. We tried the previous battery again, jiggled the battery wires, and found the problem. We then checked all of our batteries, and found multiple batteries with loose connections (yikes!).

Last year, there were several tournament matches where our robot lost connection with the field during the match for 30 seconds or so, especially when another robot collided with ours during the match. Field personnel told us, from their diagnostic screens, that our cRIO was rebooting itself during those 30-second blackouts. We had all kinds of theories about what might be happening -- perhaps we had a component that was not electrically isolated from the robot frame (especially the camera and the cRIO -- see <R36> in the 2011 rules), or perhaps the Ethernet connector to the robot radio was not a solid connection, or maybe the cRIO itself needed better shock mounting. We never did figure out that problem last year, but based on our experience this year, I'll bet you dollars to donuts we had some kind of loose electrical connection providing power to the cRIO and the rest of the robot.

So, if you find your robot is jumpy, starts and stops, has watchdog timeouts, or is losing connection with the field, I would strongly encourage you to check your robot's main electrical connections. In fact, these are excellent checks to make periodically in any case:

1. Check the connection of the wires to the battery, on all of your batteries. Make sure they are nice and tight.

2. Check the connection of the wires to the main breaker on the robot.

3. Check both ends of the wires from the power distribution panel that provide 24V power to the cRIO itself. Make sure the wires are firmly inserted into their connectors on both ends.

I hope this helps someone. These types of symptoms can be maddening, and the above checks are easy to make.