Electric Isolation

[WolfBotics]

Greetings from team 5145!

As our team nears completion of our robot, we are currently reviewing the inspection checklist. Rule 37 states that the electrical system must be isolated from the frame, however, we have discovered that the robot frame is at the same potential as the ground on our battery. After further inspection, we discovered the source of this to be the screws holding the PD to the frame of the robot. Is this okay, or do we need to mount the PD on a non-metallic mounting surface, or use nylon screws? From a safety standpoint, we are not overly concerned, as the open circuit resistance between the positive power terminal and the frame is a couple hundred kohms. We just want to make sure we are in compliance with the rules.

[Andy A.]

The short answer is that, no, this is not ok. However the mounting screws for the PDB should not be a source of a frame fault. I'm honestly not sure how they could be.

The far more likely candidate is the Crio; the chassis of this does need to be electrically isolated from the frame. Another possible fault is the camera which, apparently for some models, is also a frequent culprit.

Check the C-Rio again, carefully.

[Taylor Hawkins]

Originally Posted by WolfBotics

Greetings from team 5145!

As our team nears completion of our robot, we are currently reviewing the inspection checklist. Rule 37 states that the electrical system must be isolated from the frame, however, we have discovered that the robot frame is at the same potential as the ground on our battery. After further inspection, we discovered the source of this to be the screws holding the PD to the frame of the robot. Is this okay, or do we need to mount the PD on a non-metallic mounting surface, or use nylon screws? From a safety standpoint, we are not overly concerned, as the open circuit resistance between the positive power terminal and the frame is a couple hundred kohms. We just want to make sure we are in compliance with the rules.

Are you sure about the PD board being the problem? The usual culprits for this problem is that the cRIO frame is bonded to the negative terminal of the input leads. Usually the cRIO needs to be mounted on an electrically insulated platform (Plastic/ Wood). The other source could also be the camera. The stud that sticks out the back is also connected to the negative inside of the camera.(Not all but some models)

Just as an aside, did you drill out the mounting holes on the PD Board. Are team did that once on a practice bot and that allowed the frame to be accidentally connected to the negative terminal leaving the frame electrically conductive.

[Christopher149]

What is your electrical board made of: plastic, metal, wood, something else?

Usually, if that is non-conductive, you will be fine.

[IKE]

I saw an isolation issue this weekend at a Week 0 scrimmage. They were using a "door opener" motor from FIRST choice that was case grounded. they are going to work on isolating it.