Motor(s) randomly firing in Disabled

[Al Skierkiewicz]

I had a team report this condition at Midwest this week. Close examination showed the Talon SR was wired backwards. (input/output)

[RoboNerd01]

Yeah, we have this problem too. We are switching out our Robo-Rio with a backup to see if it changes. If it does not it is obviously a controller issue.

[Kevin Sevcik]

Originally Posted by Al Skierkiewicz

I had a team report this condition at Midwest this week. Close examination showed the Talon SR was wired backwards. (input/output)

I'm astounded that didn't just fry the Talon. I've always been under the impression that this was a death sentence for the controller.

[Al Skierkiewicz]

I thought so as well, the team wasn't sure if it was working or not. I was just involved as the motor would randomly run in disabled mode. They replaced it and I never heard back.

[Jared]

Originally Posted by Kevin Sevcik

I'm astounded that didn't just fry the Talon. I've always been under the impression that this was a death sentence for the controller.

The old victor 883's (from 2003, 2004) will still work after being powered through the motor output side. We did this with some controllers on last year's competition robot, and again in prototyping this year, and they all still worked, though we only powered them up for 10 or 15 seconds before realizing something was wrong. It's another reason why we love victors - they work for over a decade on multiple competition and practice robots!

[Al Skierkiewicz]

Jared,
While that is good news, I personally would relegate them to proto or demo service only. My Murphy's Law corollary is "anything that can go wrong will go wrong...On Einstein!"

[Kevin Sevcik]

Originally Posted by Al Skierkiewicz

Jared,
While that is good news, I personally would relegate them to proto or demo service only. My Murphy's Law corollary is "anything that can go wrong will go wrong...On Einstein!"

Mind you, some of us should be so lucky to have something go wrong on Einstein.

Thinking about it, powering through the Motor side shouldn't be different in principle from the power generation you get shoving a robot around. The H-bridge rectifies the power and it hits the control side after a couple diode drops. Which would put the control common a diode drop above common for the rest of the robot, which I imagine could cause weirdness. What I'm not sure of is what happens when you actually command the motor. On first glance, it seems like the control side should go up in smoke if you send a reverse command.

[Al Skierkiewicz]

Kevin,
You would have to get the motors up to speed to generate 12 volts in the motors. While you can get enough voltage and current to light the LEDs, I don't believe you can exceed the reverse bias maximums. Remember that the rest of the robot is also supplying a significant load to that controller when the robot is pushed. When you connect the battery, you get a low impedance, high current voltage source at 12 volts.

[Kevin Sevcik]

Originally Posted by Al Skierkiewicz

Kevin,
You would have to get the motors up to speed to generate 12 volts in the motors. While you can get enough voltage and current to light the LEDs, I don't believe you can exceed the reverse bias maximums. Remember that the rest of the robot is also supplying a significant load to that controller when the robot is pushed. When you connect the battery, you get a low impedance, high current voltage source at 12 volts.

I swear to you that I have seen the kids push a robot (possibly in low gear) hard enough to boot up the old IFI controller and all the rest of the Vics. I admit I haven't seen it with the newer control systems, so they may provide enough load that nothing actually boots. Or we've just gotten lazier and put all the bots on carts since then.

[Al Skierkiewicz]

Kev,
We were able to get the LEDs on the vics and the controller to light, I never did see it boot up though. Several of the LEDs on the controller were status lights connected to I/O on the controller and of course the backup battery was always connected.