[FTC]: Tetrix motor controller weirdness with 4 motors

[aklego]

Originally Posted by VashonRobotics

We ran into this very problem at our last competition. Two of the DC motors on the bot are the new style. Symptom: Sam module lights on, LEDS to motor controllers on. No control from game controllers EXCEPT the one NXT motor that the bot has, it still worked normally. All wiring was gone through - no tinned wire ends in motor controllers just bare copper, Anderson Power Pole connectors at battery, short USB cable with ferrite core. I think this tells us that the game controller, FCS, Sam module, and NXT were all working, the problem had to be in the Motor Controller(s). A power off and on again and it worked fine.

This is truly odd. It is still anecdotal but there are enough teams having issues with this configuration for me to believe the V2 motors are at least the trigger.

[pyroslev]

Originally Posted by VashonRobotics

We ran into this very problem at our last competition. Two of the DC motors on the bot are the new style. Symptom: Sam module lights on, LEDS to motor controllers on. No control from game controllers EXCEPT the one NXT motor that the bot has, it still worked normally. All wiring was gone through - no tinned wire ends in motor controllers just bare copper, Anderson Power Pole connectors at battery, short USB cable with ferrite core. I think this tells us that the game controller, FCS, Sam module, and NXT were all working, the problem had to be in the Motor Controller(s). A power off and on again and it worked fine.

Had a team with almost the exact issue in a Semi-Final Match. They were using a loaner NXT from another Team that had some age on it (Screen was scarred). I'm not sure if it was their NXT or the V2 motors.

[F Elliott]

We are trying to get four v2 motors to work in our drive system. We got away with two v1 motors for our Qualifier but we were the slowest robot on the mat.

Four v2 motors on two controllers, one motor per port. Servos either upstream or downstream twitch out of control whenever the motors are running.

Here is a critical new piece of information:

1. The twitching is dependent on power setting to the motors.

So we started isolating the motors ONE AT TIME and as luck would have it the last motor running on his own still caused the twitching. So we isolated it and put back the other motors one at a time and everything is good. We pulled a brand new V2 motor out of the box and hooked him up to the the bad motors DC connector and all is good.

Conclusion:
We had a defective v2 motor which was affecting everything. The more power you command to it the worse it gets. I suspect this motor has some sort of intermittent short or weakness in it or something to cause temporary high current demand that pulls power below that needed for stable power to the servo controllers.

I believe now this was the same motor I tried for our lift motor in December. It was probably shipped as defective. Like an idiot I didn't label them and just put them back in the kit.

To trouble shoot, isolate and swap v2 motors one at a time. You might have one or more defective v2 motors in your robot.

[F Elliott]

We are now running four v2 motors in our drive system and one v2 as our lift motor with no problem.

The four drive motors are wired one per port, two front drives on one motor controller, two ack motors on another, and the lift on a third. They are wired parallel into the NXT. I suspect if we put them back onto one chain it would be fine.

The problem was the defective v2 motor was hosing the DC power in the robot.

Note to self: this now makes one encoder, one servo controller, and one DC motor we received as defective from PITSCO.

Off season task: Develop a full suite of rigorous acceptance tests for anything we get from PITSCO before it ever goes near the robot.