30a breaker for 40a spot on pdb

[Jon Stratis]

Yes, the CIM's may be protected by a 40A breaker... but have you measured how much they're actually drawing? During normal (non-stall) operation, it's no where near as much. One year we were worried about current draw, and decided to measure... Turns out it was a fairly constant 40-50A during normal use - 7 total motors running almost constantly, 4 of those CIM's.

If you're really worried about it, i would suggest investing in a clamp meter. Simply put, it uses the magnetic field generated by the current traveling through a wire in order to measure that current. You can clamp it over one of the battery leads, or one of the wires going to your wheels, and see what sort of draw you're getting. It can be EXTREMELY helpful in diagnosing problems. specifically last year with our shooter... we used it after initial construction and saw numbers that we felt were too high (about 3 times what we expected). After some slight mechanical adjustments to reduce friction in the system, the numbers came in line with the expectations.

So get a clamp meter, and see if you have any issues in your system first - maybe one or more of your sprockets isn't properly aligned, generating a lot of friction and thus high current. Set the robot up to drive straight into a wall and see what happens - do the motors stall out because of high friction wheels? What sort of current does each motor draw in this scenario? (keep in mind, this is essentially the worst case for most robots)