Twitchy Motors

[Chris_Ely]

Originally Posted by evanperryg

Line resistance on a 5ft line of 22AWG PWM signal wire is about 0.08 ohms, and considering OP's cables don't even look that long, line resistance is most likely not a factor here. OP, If those are custom made cables, I'd suggest you check your terminals for faulty crimps. It's easy to mess those up. Also, try adding in your CAN runs between the PCM, rRio and PDP. It's far-fetched, especially considering the rRIO has little more than a terminating resistor for the CAN line, but I wonder if this could be a factor. Also, your breaker power runs are ridiculously long, try cutting those down, a lot.

I am not talking about the PWM cables, I am talking about the ~10ft of 6AWG power wire from the battery to the PDB - like you mentioned at the end of you post.

[ratdude747]

Originally Posted by Chris_Ely

I am not talking about the PWM cables, I am talking about the ~10ft of 6AWG power wire from the battery to the PDB - like you mentioned at the end of you post.

Seconded. I wouldn't run long feed cables like that unless I had to. At least tie them up so they're not flapping in the breeze (at least in the one picture it looked to be catching a wheel ).

[JB987]

Pretty sure his team left the power wires long knowing that this is just a test board and they will shorten them to fit the final configuration of their electronics... We'll take a look at it when his team visits us again this weekend.

[hwu24110]

[JamesCH95]

Voltage dropping that low in such a 'spikey' shape screams main power issue or battery issue.

[hwu24110]

I swapped out the battery cables for shorter ones and switched out the battery. I still experience twitching.

[JamesCH95]

What terminals are you using for the 6awg connections?
Is there any wiggle in any of the 6awg connections?
Is there any wiggle in any of the PCM/robot controller hookups?
Have you run a load test on any of your batteries? (like a battery beak)

[hwu24110]

The terminals are labelled Burndy 6 Str Cu Blue Die 374 or 7.

I don't feel any wiggle from the 6 AWG connections

I don't feel any wiggle from the robot controller connections either

We don't have a battery beak.

[nighterfighter]

Personally, I don't think the batteries are the cause of the twitchy motors, mainly because they are twitching even when the code is set to give them a value of 0. That leads me to think there is either a short in the PWM wires, causing it to send a false signal to the Talon, or the roboRIO is malfunctioning.

That being said, having loose connections aren't good. And the voltage drop isn't "good", but 9 volts won't shutdown everything.

hwu24110: Could you take a video of the motors twitching, with the joysticks unplugged and the code having the motors set to 0? If you could also get the video of the Talons that would be helpful.

[hwu24110]

https://www.youtube.com/watch?v=nj-J...ature=youtu.be

I note that when one side moved, it would always move in that direction. The other side of the robot when it twitches moves in the other direction.

[nighterfighter]

Is your driver station showing any errors?

Is your PDP hooked up to the CAN? It seems like it isn't hooked up because the lights are flashing on it.

Do you have any non PWM speed controllers you can test? (So a Talon SRX, and test it over CAN)

[hwu24110]

THe only error that is showing up is that there isn't a controller connected

Today I hooked up the PDP to a PCM that is connected to the Roborio (The team wanted to test pneumatics). I can take photos of it tomorrow if you suspect there is something wrong with the wiring.

I have a few Jaguar Controllers but I have no experience with CAN wires.

[andrewb1999]

We have also been experiencing the same twitching motors problem lately. We do not think it is an issue with the electronics as it does not twitch when the robot is enabled in autonomous. We are going to check the joysticks tomorrow and see if that could be the issue for us.

[scca229]

After watching the video, I would swear that you are running into the same issue that our bot was last year that I posted in this thread:

http://www.chiefdelphi.com/forums/sh...d.php?t=134694

Our issue is only when using PWM 0 (very bad) and 1 (not bad, but still present). Moving to 2 & 3, the issue cleared up. Our random fires were even in Disabled mode and sometimes lasting for 3 or 4 seconds at a time. Just for fun today, we tested the wiring this year using PWM 0 & 1 and the problem is still present with all new wiring/motors/controllers/code.

As a side, I'm assuming that your 4 motors are really 2 sets of 2 motors. Wouldn't you want to use a Y-cable on each pair so that they are getting the same signal at the same time and just calling them LEFT and RIGHT (or similar) in the code?

[hwu24110]

I've already tried swapping the ports 0, 1, 2, and 3 with 4, 5, 6, and 7.

As this was a test board, I didn't feel like scrounging around the PWM bin for Y cables. If you feel like that is the issue, I might try it out tomorrow.