Smoking Cortex

Currently, my team has been trying to test our robot before our upcoming competition, but within 5 minutes of driving our cortex has started smoking multiple times. Closer examination revealed the H bridge or IC U6 has burned/melted. After letting it cool and checking it all ports still functioned. We switched to another cortex, changed our wiring so heavy load motors are spread out and updated RobotC in case it was some sort of bug was occurring. Despite this, our second cortex started smoking in 30 seconds of testing. We have no idea what is happening, does anyone have suggestions or ideas?

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suggestion: don’t try it with another cortex!
what exactly was your wiring?

When a cortex starts smoking, it’s usually because there’s a bad wire in ports 1 or 10 or a motor is drawing too much current through ports 1 or 10.

This happens when there’s a short in the thermal breakers built directly into the brain used for the bridges, meaning that you’ll cause it to overheat.

Port 1=Drive
Port 2=Chainbar
Port 3=Drive
Port 4=Roller Intake
Port 5=Y cabled mobile goal lifter
Port 6=Chainbar
Port 7=Chainbar
Port 8=Drive
Port 9=Chainbar
Port 10=Drive

Note: All chainbar motors are routed through power expander

So should I go through and check all motors for shorts, if so, how?

It may be because your drive motors are drawing a lot of current, as they usually use more than the rest of the robot. This may have caused the built-in thermal breaker to overheat.

Are ports 1 and 10 still working?

The smoke may come from the onboard motor controller overheating.

There are a lot of other threads that you can look to also:

there’s no configuration in which the amount of load should cause the cortex to smoke before PTCs start tripping (someone who’s smarter than me correct me if I’m wrong). You should take the green plastic cover off of your motors, pull back the rubber thing that covers the wire and check for exposed copper. If you see exposed copper replace the motor, there is no legal way to repair it. If you still want to use the motor for non-competition use, you can wrap electrical tape around the exposed wire or use a small amount of hot glue. Also, when testing motors, to avoid frying the cortex, I like to plug the motors into a 9v battery with the backup battery connector. Another tip is to avoid using ports 1 and 10 if possible (though sometimes you just need all 10 ports), if you blow an internal h-bridge you have to either replace the cortex or change the code to not use whatever port you’ve blown. If you don’t use ports 1 or 10 and you fry an MC29 that’s a quick and easy replacement (well, depending on how well you do your wiring).

do ports 1 and 10 still work? like @henryl said, your drive could’ve overheated the built-in motor controller.

Have not tested it since the incident but likely so, when it started smoking we were not driving the robot, just the chainbar.

Ok, I will plan on checking for exposed wire, hopefully the problem is simple as that. Thanks for the help

Dont know for sure if 1 and 10 still work, will have to check

It could be a motor controller shorting; we’ve had that happen before (although it never killed a Cortex). does it still happen after the initial smoke? If so, you can use one of your smoked Cortexes and individually test each motor/controller.

We’ve also had a quadrature encoder short that made all of our motors super week. It could be a sensor.