I was trying to drive my robot last week and it would work fine but then it would slow down and eventually stop completley. It has been this way for a week now and i have changed the cortex, motors, motor controllers, the program, and I also downloaded the latest firmware. I was wondering if anyone else has had this issue and if anyone knew how to fix it.
How many motors are you driving with, gearing, approximate weight, and ports they’re plugged into? If you’re running, for example, 6 motors on ports 1-6, and pushing them to their limits, you’ll easily trip the ptc on ports 1-5.
There is only four motors in total, the drive motors are on ports 1 and 2. The two back wheels are attached to the motors and the front two are attached by a chain. Currently the gearing on the wheels is 2 to 1. The weight of the robot is relatively light because we took the arm mechanism off of it, I would say that its only around 5 pounds right now. We took the gears and the chain off of it yesterday and attached four motors to the drive train, one for each wheel, but that didn’t help either.
does the chain encounter any friction? we had our drive’s chain way too tight earlier this season, and it did exactly what you describe
We have not tried that, however yesterday we took the chain off and added two motors to the front and we still had the same problem.
the wheels could be rubbing hard against the sides of the metal?
I don’t think that is it either, the wheels are not close to the metal
hmm… are the shafts bent?
I don’t believe so
Nope, I just checked, all of them are straight
If you wait a while after it stops, can you drive it again? I ask because your description sounds like classic motor stall. If you wait ~10 seconds, and you can drive it again, you’ve got motor overload.
Have you tried plugging the motors into ports 2 and 7, for example, so they’d be on different cortex circuit breakers?
I would suggest against using a combination of ports 2-9 and ports 1 & 10 (you mentioned you’re using ports 1 & 2). Ports 1 & 10 have a built-in motor controller that has different performance characteristics than the external motor controllers used in 2-9. I don’t think this is the source of your problems, but it’s better—when you’ve got motors that need to work in tandem, like a drive train—to use the same type of port for both motors (in your case, use either 1 & 10, or some combination of 2-9, but not 1 & 2 like you described above).
Yes that is exactly what happens, it stops and then ten seconds later I am able to use it again. When I said I was using ports 1 and 2 I was wrong I meant to say 2 and 3 however I will still change the ports in case that is the issue. Thank you for your help!
@Videogamer2002 - if that’s the case, then it means that your motors are stalling, because you are asking too much of them. I wrote an article on motor overload (stall): https://renegaderobotics.org/motor-overload/.
Here’s a helpful quote from the article, from coach Todd Ablett (sorry, I don’t know his forum name):
From your description, it doesn’t seem like you’re putting that much stress on the motors, but everything you’ve described sounds like motor overload, especially the fact that you can drive again after waiting a few seconds. So, you’ve got chassis only, with one motor on each wheel, and this still happens?
Have you used the RobotC datalog to see what the motors are doing as you drive? In case you’re not familiar with the datalog, I wrote an article on it too (yes, shocker): https://renegaderobotics.org/robotc-datalog/
I have not tried looking at the datalog yet but when I went the other day to help the kids I realized that when they were testing their drive motors they would push the joystick forwards and backwards rapidly which I assume is part of the problem. Thank you for all of your help!