Troubleshooting motor controllers

[Rambot 4525]

We shut our robot off after a regional competition and when we got it back to school and fired it up, none of the motor controllers are working. It is unlikely all 7 are bad! We checked all connections and reinstalled software but there is no data getting to the controllers. The victors blink amber and spin nicely but no communication. We are a rookie team looking for suggestions. Any ideas?

[404'd]

When the robot is enabled, the victors should not blink yellow, they should be solid yellow. If they are blinking while enabled check the cable running to sidecar from cRIO module and check for power to sidecar.

[Rambot 4525]

We swapped out the ribbon cable that came with the kit for a computer cable, and got the same result. The sidecar lights up and the cRIO has power too which we also reset. Have ordered a new cable to connect the sidecar but are waiting for it to arrive.

[Jon Stratis]

How are you connecting to the robot? When you look at the driver station, does it show a green light next to communication and next to code? Does the driver station allow you to enable the robot? What is the robot signal light (the big orange blinky light) do when the robot is enabled?

It's a lot of questions, but answering them should give us a better idea of what the real problem is.

One of the most common issues when coming home from competition is the radio - you get it set up at competition with some wireless encryption stuff you don't have back at home. Download and run the "2013 FRC Bridge Configuration Utility", to make sure you can connect over wireless to your robot. You can find it here: http://www.usfirst.org/roboticsprogr...ical-Resources

[Rambot 4525]

thanks for getting back to us. We are connected wirelessly, and all lights are green on the drivers station. The robot can be enabled by the driver station and the orange light stays solid (it did that at the competition too and worked fine - very strange that they let it pass inspection). We have reloaded the software from the site you listed. Does this help?

[404'd]

Are you using any pneumatics, do they work? Or are you getting a battery voltage read out on the drivers station? I'm interested to know if the cRIO is configured correct and other modules are working.

[Rambot 4525]

No pnuematics and the only other mechanical device is a car door actuator that runs through a spike relay which is the only thing working. Battery voltage looks ok and everything else looks configured correctly.

[Jon Stratis]

On the digital sidecar there are 3 LEDs (BAT, 5V, and 6V). Are all three fully lit up?

[Rambot 4525]

Jon, all three are lit up.

[Jon Stratis]

From everything you've said, it sounds like everything is correctly hooked up electrically - ie nothing "shook loose" on that side of things.

Use a multimeter and make sure that the GND and +5V pins for the PWM wires you're using are reading the correct voltage. If not, your sidecar might be busted.

Do you have access to an oscilloscope? It would be nice to scope the PWM signal coming out of the digital sidecar and make sure it looks correct. If not, you can try using a multimeter set to AC Voltage. It's not perfect, but if there's no signal, you'll read 0V, and if there is one you should read a voltage.

Have you checked that all of the PWM wires are seated correctly? Sometimes they can be loose, and riding around in the back of a truck on a long bumpy drive might be enough to shake them just loose enough from the Victors that you don't get a signal anymore. It would be odd for this to happen to all of them at once, though.

Are you sure the code hasn't changed?

[Alan Anderson]

Have you tried connecting using a physical cable instead of wirelessly?

Is your D-Link set to Bridge mode or to AP-2.4?

What is each of the wires from your orange Robot Signal Light connected to?

Are there any messages in the display window on the Diagnostic tab of the Driver Station?

Are you using a 4-slot or an 8-slot cRIO?

Which slot is the NI 9403 Digital module in?

[Ether]

Originally Posted by Jon Stratis

If not, you can try using a multimeter set to AC Voltage.

Some DVM's use half-wave rectification for AC, and if you have the DVM leads connected the wrong way you'll read zero volts. If you use DC, you'll read voltage regardless of polarity.

[Rambot 4525]

Have tried the physical connection with same result. The D-Link is set to AP- 2.4 and the amber light is connected to the sidecar at the RSL site. No messages on the Driver Staton and it is a 4 slot cRIO. The NI 9403 Digital module is in the second slot from the front (where the logo is).

[Jon Stratis]

Originally Posted by Ether

Some DVM's use half-wave rectification for AC, and if you have the DVM leads connected the wrong way you'll read zero volts. If you use DC, you'll read voltage regardless of polarity.

Good to know... I've seen with mine set to DC the results can be inconsistent, as the sampling period doesn't handle square wave forms very nicely. With AC, I've always seen decent results for quick testing. It just goes to show that testing I might do for a team in their pit can't necessarily translate very well over the internet!

[MichaelBielecki]

I did a quick search and found this online:
( http://content.vexrobotics.com/docs/...al-9-25-06.pdf ).

From what I read, a "Flashing ORANGE indicator on power up" means "No PWM signal." This is probably caused by the sidecar. Since all motor controllers are not working, it is unlikely that all of them had something happen to them that would be causing this. It is more likely that the source of the pwm signal (the sidecar) which they all share in common is causing the problem. A couple things you can do to check the side car is to first look at it and see if there is anything visibly shorting or if something is plugged in backwards. Another this that could be causing this is chips. You can try to clean out the chips if you see any and try again. The signal light pattern would help identify the problem. Is the RSL blinking when you plug it in or is it a solid on or off? I ask because one of my teams sidecars went bad and the signal light would not turn on. If you don't see a problem, you can try unplugging everything from the sidecar except for one motor controller. See if it works. If not, try getting a new, unused motor controller if you have one to test the sidecar.

I hope this helps