Re: [HELP] Digital Sidecar troubles
 

Move one, check it works, then add another. If you change more than one thing per test, and a problem shows up, you don't know which change was the important one.

Re: [HELP] Digital Sidecar troubles
 

You may have to do it both ways, but I'd start with having only a single connect on at a time.
One alone connected to the DSL will show a short on individual lines. Good if there is more than one connector at fault.
Don't assume any of the connectors are good if you find a bad one. Test each and every one.

If the fault is related to the total power draw (why I asked how many), then you'll have to repeat and work your way up to having all of them connected. Or finding out how many connections until it causes a fault.

Just be systematic about it.

Re: [HELP] Digital Sidecar troubles
 

Check that it works after each individual change.

The idea here is to further isolate the problem. If you plug in one PWM cable, and it still works fine, you know that one cable (and the attached speed controller and motor) aren't causing your issue. However, when you plug one in and start having problems, then you've narrowed it down to that specific branch. (This is assuming it's not a broader problem related to the number of controllers being used)

Once you've narrowed it down to a specific PWM branch off the Digital Sidecar, you can then figure out the problem pretty quickly. For example, if the PWM is controlling a speed controller, disconnect the motor outputs from the speed controller and see if you still have the problem - if you don't, the issue is likely with the motor or the wiring between the motor and the speed controller. If you do, still have the problem, try replacing the PWM cable. If that fixes it, you know there was an issue with the cable. If it still isn't working, try replacing the speed controller.

Generally speaking, when debugging issues like this, you aren't trying to find the problem directly - you're trying to eliminate as many possible locations for the problem as you can. This is something I do all that time at work. Narrow down the scope of what you're looking at, and you'll find the problem easier.

Re: [HELP] Digital Sidecar troubles
 

Well...an unencumbered sidecar shows all the lights. That's about all the sidecar will do. Tried the first 3 PWMs individually in this sidecar and didn't get any response. I don't believe it's the cable either; tried it in an older robot and it worked fine. Could it be that the cRio bus itself is bad? We've had that go wrong before, but we've already switched the bus for a different one. I'm not sure about their failure rate but I'd be hard pressed to believe both went bad with in a matter of days.

Re: [HELP] Digital Sidecar troubles
 

At this moment, we have a new PDB on the robot. All we have plugged into the PDB is cRio, Sidecar, and one Jaguar. Attached to the Jaguar is one CIM, going through a CIMple box, to a 6in KOP wheel. The Sidecar is attached to the cRio using a DB37 connector. The lone Jag is in port 2. The sidecar, when both disabled and enabled, shows all three lights strong. Yet when we enable it the Jag itself doesn't enable. (It's not the Jag that's the problem, none of the motor controllers [Jags or Victors] would enable.)

Re: [HELP] Digital Sidecar troubles
 

Of course, make sure your software really is talking to port 2.

OK, with only one PWM, power is solid. Good
Are you seeing PWM to the motor controller? Use an AC voltmeter on the white wire, robot enabled.
Verify a good ground path, about 0 ohms from the black PWM wire at the motor controller to battery negative (all power off)

Let us know. The next step is to check the data signal coming out of the digital bumper on the cRio, robot enabled. Got a spare digital module?

Re: [HELP] Digital Sidecar troubles
 

Programming is defintely talking to port 2.

Sidecar lights went out again. When we're plugged into the cRio via DB37, we have no 6v light, and 5v light goes out as soon as we enable. This problem showed up recently. For a half hour tonight we had all three lights strong.

When you said check PWM, can you elaborate on how to check?

EDIT: If unplugged from the cRio and we still don't have all three lights, does this mean the sidecar is fried? If yes then does anybody know what typically fries a sidecar? This new sidecar has been hooked up to nothing but our simplistic setup, and must have been fried sometime in the last half hour.

Re: [HELP] Digital Sidecar troubles
 

Cal,
The LED conditions you are describing are typical for no power to the DSC. The DB37 connector can back feed enough current into the DSC to light the LEDs with no current demand. When you enable and start drawing current in the DSC, the LEDs go out or significantly dim because there simply is not enough current available through the DB37.
Please double check the polarity of the power supply wiring to the DSC and inspect carefully the power connector, pull on the wires.
There is a method of reverse polarity protection in the DSC but I have seen it fail with abuse in the past.
You said this DSC worked in another robot, move it back to that robot to check it.

Re: [HELP] Digital Sidecar troubles
 

That is very suspicious. Once again, where is the 12 volt input power to the Digital Sidecar coming from? What exactly is it connected to?

Re: [HELP] Digital Sidecar troubles
 

I can elaborate, but read Al's response above first, then help us by answering Alan's question.

To check a PWM signal, put an AC voltmeter between the white signal wire and the black ground wire. It should read about 5 volts AC, or thereabouts, while the PWM is actively being commanded (used). This will vary slightly from full reverse to full forward, but only a tiny bit.

Re: [HELP] Digital Sidecar troubles
 

We checked over the wiring particularly closely and the polarity is correct, the wago connector is intact, the wires are secure, and we're getting 12v where we're supposed to get 12v.

The 12v input power to the Sidecar is coming from the Power Distribution board from a 20amp fuse slot.

I shall check that again tomorrow, when I'm by the robot.

Thank you for your help and hopefully we can get this resolved soon.

Re: [HELP] Digital Sidecar troubles
 

One more thing that I don't think anybody has mentioned: you're using a full-charged battery, right? Weird things happen when battery voltage drops too far, including PDB whine.

Re: [HELP] Digital Sidecar troubles
 

Yupp, full batteries. We've switched batteries twice now.

Re: [HELP] Digital Sidecar troubles
 

Cal,
Have you moved this DSC back to the other robot? Does it still work over there?
If the wiring is all the same, there is a remote chance you have a defective WAGO connector at the DSC. It may have a bent/broken pin inside the connector, or the pin in the circuit board is broken or improperly soldered.
You won't be able to to check the power supply voltage on the DSC board without taking the cover off but that would be my next step if I was working on this problem.
For a long shot, I would open the case anyway for inspection. I have had on rare occasions, found loose material that floats around inside, causing problems in one orientation but not in others. Or a crack in the board, allows it to work in one mounting but not in others.

Re: [HELP] Digital Sidecar troubles
 

A voltmeter is a wonderful tool for diagnosing FRC electrical systems. A useful digital voltmeter can be had for $10 (if you shop for a sale price).

If you're using an inexpensive meter (like mine) that doesn't do true rms, it will read 0 volts on the AC setting when trying to measure the PWM signal if you have the test leads reversed.

That's because in AC mode it rectifies and filters the signal and assumes it's zero-offset sinusoidal in order to get an AC reading. If the test leads are reversed, the meter's diode will block the PWM signal voltage.

If the test lead polarity is correct, it will give a reading. As you vary the command from full forward (2.0ms pulse width) to full reverse (1.0ms pulse width), the voltage at full reverse will be approx 1/2 of the voltage at full forward (because the duty cycle at full reverse is 50% of the duty cycle at full forward: 1.0ms/2.0ms=1/2).

Also, you will get different voltage readings depending on the PWM period you are using (e.g. Jag vs Vic driver).