Andymark Hall Effect sensor warning

Attn mentors,

In order to teach your electrical team some debugging skills, read on:

When going through our pre-inspection checklist, we discovered a path between battery negative and the chassis. … These hall effect boards (https://www.andymark.com/products/hall-effect-sensor) have got ground-plane copper flowed all the way out to the mounting holes and when you mount them to the rails in this kit (https://www.andymark.com/products/dart-sensor-kit) using the supplied bolts, you will break through the solder mask and create a path to ground.

Happened to “a friend”.

@Nick_Lawrence

We’ve used these boards in a few places over the years and always fastened them with zip ties through the mounting holes (to plastic brackets). Might consider using heat shrink and zip ties to mitigate this issue

We made nylon ‘washers’ out of scrap zip-tie and a drill bit. Glad we discovered it before inspection. We were able to pass inspection in one round.

I’ve seen more frame short to ground issues this year than any previous year i’ve been inspecting. One from a damaged USB cable. One from a damaged PWM cable. 4, on the same robot, from 4 CTRE Mag Encoders, shorting through the mounting screws for the case.

If you find your frame is shorted to ground (or +12V), I recommend first unplugging the RoboRio and check again. If it goes away, you can plug it in and start unplugging connections there and testing until you find it. If it doesn’t go away, then you can do the same for your speed controllers, and all other parts of the electrical system. Be aware that you could have multiple shorts at the same time, which makes diagnosing especially difficult! If you suspect that might be the case, get everything unplugged and plug it back in, one at a time, testing each time until you find the issues.

yup. We started removing fuses with the meter on “annoying beep” mode. It was when we removed the encoder cables from two Spark MAXes that we homed in on it.