We have one of the old style cortex microcontrollers and 3 times in the last 6 months we have had it has become very hot to touch, motors have stopped working properly, sensors reading funny values (pot which had been working well had a reduced range from 2-90 but still turned normally, ultrasonic sensors were not working and message “ping timed out”), not syncing with the joystick and the 2 lights which are normally green go an orange green colour (not green but not orange) - has anyone had similar problems or ideas to prevent it?
Has many wires across the front, but nothing unusual compared to what we have seen on other robots. Apart from wires there is nothing is front of it for two inches. Back is completely open, at the back of the robot, apart from 2 1x25 bars which is is attached to. I dont think positioning is the cause of overheating, but thanks for the suggestion
Hey Jacko, I had the exact same problem, But i created this awesome cooling device, A few pumps of this is going to cool it down instantly. I am a avid user of this.
thanks for the suggestion, we actually didn’t think of that! We would still like to find the cause of the problem though, to help us find a more permanent solution. Pretty sure the cortexs aren’t designed to heat up so much they stop working and if it happened in game it could ruin a whole competition for us… Pumping cold air onto a hot cortex also makes one of our more paranoid team members worry about condensation forming inside the microcontroller
When you say ‘the exact same problem’ do you mean just the overheating, or all of the symptoms we described?
Could you tell us more symptoms you had, incase this helps others answer our question?
We thought the best way to cool it down quick we would remove the cover of the cortex and blow cold moist air into it and after the competition i took it home and put in the freezer for a few days. Afterwards i took it out of the of freezer and put it in the microwave on defrost for 30 minutes ( Serving size recommended 4)
Just 11 degree’s cooler you will gain 1 horse power at the wheels.
Hey, we’re looking for a serious reply to a pretty big problem we’re having. Please help us out. Jokes are appreciated, but not always so much when everything seems to be going wrong less than a week before a scrimmage
There only only a few parts in the Cortex that can generate much heat.
One of them is the 5V regulator which is located just behind the 9V backup battery connector. If something is shorting the Red/Black wires on a digital or analog I/O port, that could cause this regulator to overheat, and it would interfere with the operation of the analog and digital ports.
Also, the H-bridges that drive motor ports 1 and 10 can generate some heat. If you have open 3-wire motor ports, try moving 2-wire motors out of 1 & 10 to external Motor Controller 29s plugged into a 3-wire motor port.
Thats about it. There isn’t much more inside the Cortex that should be able to put off noticeable heat (more than once).
That sounds like the VEXnet key itself is the source of the heat. I don’t think there is anything near the key receptacle that would be able to get hot other than the key itself.
Have you tried using a different key?
Does it still happen if you run the robot tethered?
We tried using a different vexnet key, and still had the same problems. The key we tried worked normally in another team’s cortex, as did the potentiometer that is giving us trouble. We will try running the robot tethered tomorrow and let you know what happens.
Thanks
Hi, it happened again to us today at a scrimmage… the lights went orange and all sensor ports stopped working including pneumatics… Any ideas? we changed to the spare half way through the day…
Interesting - and it was the Cortex getting hot, not the key?
It could be. A shorted sensor cable or USB extension would cause the 5V regulator to generate significant heat, and would cause all the sensors to malfunction (since they all share the same 5V supply).
A shorted PWM cable would probably cause the PTC over-current protection to trip, but I suppose it could manifest in other ways if the short was between the white and red wires.
Are any of the sensor/PWM cables themselves hot? If those wires are shorted, I’d expect them to feel noticeably hot.
I would try to isolate the problem by trading out everything attached to the microcontroller, one item at a time.
Thank you for ll of your help, we had an extension cable for a jumper clip which we noticed had a damaged wire and was slightly exposes so we think this may be the cause
and if it happened in game it could ruin a whole competition for us… Pumping cold air onto a hot cortex also makes one of our more paranoid team members worry about condensation forming inside the microcontroller