Let's Collaborate: FRC Electrical/Systems Troubleshooting Manual

[Al Skierkiewicz]

Originally Posted by JesseK

PWM Cables
Use clear nail polish. It's non-conductive, comes of cleanly, and is easy to cleanly apply.

Jesse,
I have to agree on the rest of your post but I am firmly against the use of permanent or semi-permanent attachments for critical connections. Adhesives (hot glue, nail polish, super glue) should be avoided when you may need to change a defective part quickly during a finals match. I recommend that teams find a way to attach the PWM cable near the device with a tywrap. The Jaguar has some clips molded into the body for this purpose. If the cable is holding down the connector, i.e. no slack, then the connector cannot pull out. A simple cut with a small side cutter is all it takes to remove the cable. We use punched aluminum sheet to mount electrical items and the holes are perfect for this purpose.

For my two cents, learn early that a voltmeter does not tell you the condition of the battery unless it is under load. Dead or near dead batteries will cover about 50% of all electrical problems but will read 12 volts on a voltmeter with no load. If many things do not work on the robot that have before, change the battery. Don't believe that a student gave you a charged battery try another one. The Crio senses battery voltage through the jumper on the analog card for module one only. If the battery voltage falls to 5.5 volts, the Crio disables all outputs. When the battery voltage rises, the Crio will start operating again until the battery falls to 5.5 volts. Watch the drivers display to check battery voltage. The power supplies in the PD will fail at about 4.5 volts. When the 24 volt supply fails the Crio reboots, the 12 volt supply failure causes a reboot of the gaming adapter and a five volt failure causes the camera to reboot. They do not all fail at the same time, so as luck would have it, you may not have communication re-established following a power brownout.
Learn to listen to the robot, it is talking to you. LEDs will tell you a lot about the health of all the systems, sounds will tell you if something is wrong mechanically, and for what you can't see or hear, smell will tell you if something is overheating or has burned. You will never forget the smell of a burned FP motor or a bad speed controller. While we are on the subject, the LEDs on the sidecar can glow dimly with current leaking through the data connectors. Make sure that they are bright and supplied with a good external power connection. Use your voltmeter at the power in connector to insure that the sidecar has power.
For your benefit and those of your inspection team, don't hide electrical parts where they can't be seen. If we can't see the LEDs on everything, we can't help you play.