Safety Board relay issue

A project log for FSAE 2014 Electric Race Car

F-1 Electric Race Car

richard-johnsonRichard Johnson 08/19/2014 at 03:440 Comments

So one issue we had at comp is a little relay chatter. I thought it was battery issues and let it go for the time. We got back and it was really annoying me. So I pulled the safety board out of the car and ran some tests on it. Come to find out the issue rose its' head w/o relays attached. It had to do with our ~5 second precharge timer. We had a R/C timer go into a opamp with a pot to set the device as a comparator.  I am guessing the op amp didn't have enough open loop gain to go from low to high cleanly. So we got this high ringing on the output. We fixed this with a pull up and pull down resistor in the precharge system.