[HELP] Digital Sidecar troubles

Technical Electrical
#1

We’ve managed to isolate our problem to our sidecar. After that, our team is completely lost as to what the problem is. We’ve switched through some sidecars but none seem to work, so it may be something wrong with the set up. Nothing electrically has changed between when we last competed, CTTD 11/3/12, and now. Our sidecar is set up, but suddenly the 5v and battery light are spazzing out. As well, we only sporadically get power to the RSL. Any suggestions? The lights are fine when we’re disabled, but once we enable then all the spastic problems start happening. We’ve gone through and checked for shorts, but didn’t find any.

EDIT: Also, we’re getting a high pitched whine from the PDB…any ideas on that, and if it’s an issue? We do have a replacement PDB but we’d rather not have to replace it if we don’t have to.

#2

Every sidecar problem we ever had was caused buy the cable and not the sidecar.

Check the cable.

#3

Sounds like you have power problems, check that all the fuses are good and if the wago connection is not loose (the cords tend to slip out over time). Also, I’d check to see if the cable from the cRIO to the Sidecar is fine, since the robot’s game state seems to have an influence, although I don’t think that’s the problem since you say it worked in CTTD and hasn’t changed since.

#4

We’ve managed to isolate our problem to our sidecar.

We’ve switched through some sidecars but none seem to work

From the above two statements it doesn’t seem logical to conclude that the problem is the sidecar.

#5

We’ve also found the ribbon cables to be finicky.

#6

We’ve had this problem quite a bit. For us it’s been caused by a digital I/O or PWM connector being shorted out. You should try running the robot with nothing connected to the sidecar, then add the connections until you find the bad one. We’ve found that it’s quite easy for the DIO cables to get damaged and short together and cause the 5V supply on the sidecar to drop out. We’ve also seen a very similar problem to this where all of the outputs on the sidecar drop out. This is caused by the 9403 digital module losing power. If your cRIO power connector is loose, it can cause the digital module(the part that goes in the cRIO, not the sidecar) to brown out when the rest of the cRIO doesn’t.

#7

A few thoughts that might help diagnose the issue:

  • unplug the DSC and hold a multimeter up to the plug. Read the voltage when the robot is both enabled and disabled. Please make sure you do so safely! This should mimic the battery voltage, so it won’t hold steady at 12V.

  • Even if you don’t have a short, you could have an open circuit. I saw a team at an off season competition a month or two ago that used 22 gauge from the PDB to the DSC, and managed to burn it out completely - broken wire, burned/melted insulation… it was ugly. With a broken wire, you could see intermittent operation.

  • Remove all the breakers from the PDB except those required for the DSC and the analog breakout board. Do you still hear that whine? Do you still see the incorrect behavior on the DSC? If not go through replacing the breakers one at a time - at some point you’ll start encountering your issues again, but this may give you a different place to look.

  • Are there any red LED’s on beneath any of ports on the DSC? Those are there to tell you if there is an issue (a short) with that port!

#8

Well we tried switching cables earlier but didn’t get much progress in that respect. We’re not using the ribbon cable; we’re using DB37s

I’ll check out the module and cRio power tomorrow but previously we’ve switched the module for another one and also didn’t get much progress either. We’ve had that problem before, and it solved by switching. I’d rather not think of the odds of both busses being bad.

I’ll have to try all of these tomorrow as well. We hooked up with 18GA on 20amp so I’d be surprised if we burned that. I don’t believe there were any red LED’s showing yet.

#9

If you try the suggestions here, still can’t find the problem, and you’d like some on-site help, PM me. My schedule isn’t too horrible this month, so we can probably find a mutually agreeable time for me to visit your shop and take a look.

#10

I remember seeing Joe Hershberger (jhersh) diagnosing a problem at the Alamo regional once that mystified all present. On your list of things to check please add the following:

The pins on the DSub connector on the cRIO may get bent if the module is not inserted correctly. It is unusual, but I’ve seen it happen twice now. Depending on which pin is bent, the module may power up and report fine, but may not function properly.

#11

Huh. That’s an interesting theory. Although I’m not by the robot right now, that sounds like it might be our problem, as our cRio is a little bit out of the way and somewhat difficult to get to directly at the moment. We may have jostled a pin or two when we replaced the module.

#12

But it doesn’t explain the whine you hear. I didn’t read that part when I was looking at the post originally. I provided the note about the bent pins just because I don’t typically see it when this kind of thread pops up. And I know it happens because I’ve seen it multiple times.

Now, for the whine. Is it high pitched or low? It is either the sound made by the constant tripping of a circuit breaker or an audible harmonic emitted by one of the switch-mode power supplies in the PDB (5, 12, or 24V). Also note that the sidecar and the analog breakout also have switch-mode supplies in them too, so be sure that the noise isn’t coming from a sidecar next to the PDB and you’re just assuming it is the PDB.

The sound of a circuit breaker constantly tripping will (in my experience) makes a lower pitched noise.

The sound of the switch-mode supplies will be higher pitched and may change frequencies based on the current being drawn. This may be caused by the most popular robot construction sin – metal debris in the electronics.

To isolate whether it is the switch-mode supplies rather than a circuit breaker, you can remove all circuit breakers to see if it is the PDB, and then start adding one back at a time as others have suggested.

Since the failure didn’t go away after changing sidecars, I doubt that the sidecar is the issue. And I doubt that it is a bent pin since I can’t think how the loss of connectivity would generate a whine.

#13

I know the sound of a constantly tripping circuit breaker. It isn’t that noise. It’s a high pitched squeal (Or whine as my girlfriend called it). Our sidecar is fairly remote from our PDB (a good 18"-24"), so I don’t think it’s the sidecar.

As far as clarification as to why we believe it’s somewhere along the line of the sidecar, or perhaps the DB37 cable, would be that it we are still able to enable the robot, get spotty control of the robot, and then we die out. We tried switching the port the sidecar gets power from and still have the same problem.

#14

A spotty power supply would give you intermittent control and produce the sound you describe. If you can, replace the PDB completely; if not, your best option is to either send it in for a replacement or if that’s not possible, open it yourself and clean out swarf.

#15

Does the power board continue to whine when unloaded? Meaning if you pull all the connections and energize the board do you still hear it make noise? This would mean removing all the breakers, disconnecting the radio, cRio, and camera (basically having an empty board). After it is disconnected, power the PD board up from the battery and see if you still have the whine.

#16

I wouldn’t worry too much about the whine.
It’s probably just the boost converters.

#17

Haven’t tried unloading the PDB nor have I tried removing the fuses yet. I’ll have to try tomorrow afternoon (~Noonish if people would like to check in.) We have spare PDBs, I would just rather not have to go through and rewire the entire PDB . If it comes down to that being the problem then I might just have to do that.

#18

Scott,
Whine in these power supplies is normal although often very low in level. I have to ask what the LEDs on the DSC are doing. Are they all ON (qty 3) at the same brilliance? Does the RSL LED (the one on the DSC board next to the white RSL connector) flash when the robot is enabled? Is the 6 volt LED changing? This is usually metallic debris in the servo output connectors. Do you have any of the 6 volt jumpers installed on speed controller outputs? Do you have any relays connected? What do their LEDs look like?
If all of these appear normal, try removing all inputs and outputs from the DSC and then try installing them one at a time if the DSC appears normal with everything removed.

#19

I was interpreting this to mean that you tried swapping out the sidecar (with at least two other sidecars) and it didn’t change the symptoms.

Is that a correct understanding, or did you mean something else?

#20

Unfortunately, this whine happens to be an audible, high pitched whine.

I have to ask what the LEDs on the DSC are doing. Are they all ON (qty 3) at the same brilliance? Does the RSL LED (the one on the DSC board next to the white RSL connector) flash when the robot is enabled? Is the 6 volt LED changing?

Battery light generally goes completely off, and the 5v light flickers or simply is on at a very low level. The 6v LED stays fairly strong throughout the operation. RSL LED flashes at it’s normal speed, though occasionally doesn’t turn on all together.

This is usually metallic debris in the servo output connectors. Do you have any of the 6 volt jumpers installed on speed controller outputs? Do you have any relays connected? What do their LEDs look like?

We don’t, or at least shouldn’t, have any servo jumpers installed. I’ll double check when I get to our facility today.

If all of these appear normal, try removing all inputs and outputs from the DSC and then try installing them one at a time if the DSC appears normal with everything removed.

Will do.

Thank you, all of you, for your help. It is much appreciated.