So our robot was working perfectly yesterday on the practice field, but not today: when we plug in our two encoders to the digital sidecar (DIO slots 1-4), the 5V power on the sidecar fails (and thus we lose all pwm control and become a cute purple brick). Without the encoders plugged in, there are no shorts between power/ground and power/signal…
We tried replacing the encoders, the wires from the encoders to the sidecar, the sidecar, the cable from the sidecar to the bumper, and the bumper… Even replacing ALL of them yielded the same result.
Any ideas? It’s rather too late for FLR – we’ve established ourselves as a rather good fender defense and are for this regional comfortable in that role – but for Buckeye in two weeks it would be nice to have actual speed control on our shooter…
We’re stumped. Any assistance anyone could provide would be most appreciated.
Send a private message to EricVanWyk here on CD to bring his attention to this post. He is VERY familiar with the digital sidecars and its various failure modes.
Without having hands on, this is difficult to help troubleshoot, but what the heck, troubleshooting systems is what I’ve done for a living for 30+ years.
The very first thing you need to ask is: “What changed between yesterday and today? What was the last thing you did?” That might point you in the right direction. The fact that it was working yesterday and is not today is baffling. Something must have changed. If you can’t think of anything at all, try the steps below, maybe you’ll find something.
Start by plugging in one encoder at a time. If either one makes you loose the +5vdc, you have narrowed down the cause. If neither does by it’s self, what about trying to move them to a different input,. Same result?
If neither kills it by it’s self, then maybe the power supplying the board it the issue.
What kind of encoders are you using, and how are you wiring them? Are you positive that the encoder wiring is correct?
I don’t have any magic answers, but can suggest a few things to try…
We use the USDigital encoders exclusively, although different models (generally E4P and E7P) and wire them with the 4-pin USDigital cable going to two separate 3-pin PWM-style connectors, but with each connector only using two conductors. One connector will have “A” and 5V; the other connector will have “B” and GND. With the way that we wire them up, it is essential that the connectors be wired the correct way round, and it is easy to get them wrong. When they are wired incorrectly, wierd sidecar behavior can result.
Another thing to check – is the ribbon cable from the cRIO module to the Digital Sidecar ok? We had a cable which had been damaged due to a robot accident and had intermittent shorts in a couple of the conductors.
I would also suggest checking the power connections to the digital sidecar very carefully. Replace the circuit breaker if you have any reason to suspect it. Consider temporarily replacing the circuit breaker with a small (10A?) automotive fuse – if it blows, it will do so completely and finally, making it easy to diagnose the problem.
This was literally a question of “it worked last night, we turned it on and went out to the field and it stopped working halfway through a match”.
Indeed. Whatever it was, we can’t find it.
Did that. Both do it. …and they do it if they’re new or old encoders, new or old cables, old or new sidecars, and old or new DIO ports… All with new or old sidecar-to-bumper cables and new or old CRIo bumpers.
We unplug the encoders, everything else works fine. We can’t seem to even come up with something else to check.
Another thought – have you tried moving the encoder pins to different pins – say 7-10 instead of 1-4? There may be a physical problem with the pins you are using on the sidecar.
Replacing the sidecar is a painful change (with the many cables for PWM robots) but might be worthwhile. You should be able to get one from the “spare parts” desk at the tournament.
That being said, a few questions (some elementary, but bear with me):
Which encoders are you using? (I assume the E4P from USDigital, which is what’s standard in the KoP)
Is this behavior consistent no matter which DIO (technically, the term is GPIO ;)) pins are used? That is, it doesn’t matter which pair of pins is connected to the encoder?
Have you double checked the encoder wiring setup? (i.e. made sure each line is isolated and not shorting to something else, and that you have +5 to +5, A and B to GPIO, and GND to GND)
Do other digital sensors work on the GPIO pins? (If you don’t have any on hand, see if any other teams have spare photoelectric sensors that you could play with).
You said the 5V power fails; I assume this means that the 5V light turns off while the 6V and BAT lights stay on? (note to Eric: p3 of the spec sheet seems to have the 6V and “Power Input good” labels reversed)
What do you mean by bumper? The 9403 module (the 37-pin module that plugs into the cRIO)? Something tells me that you’re not plugging the DB37 into your bumper… :ahh:
Since the only remaining common at this point is the cRIO port, have you tried using a different slot for the module? Although the cRIO probably isn’t your point of failure, replacing everything else does nothing else, soo…
When you replaced parts, did you restore the original after finding that the replacement didn’t fix the problem? (If a replacement has a problem, it introduces another problem to the system that you’re likely to not notice, because fixing the original problem won’t fix the system).
Pat,
The power supply in the DSC is capable of several amps so it should handle two encoders. Is there any chance that someone unplugged the encoder connectors and put them back reversed? Some devices are reverse polarity protected and would produce a short if wired backwards and thereby cause the 5 volt supply to shut down. It is also possible that the power feeding the DSC has a loose wire. Does the 6 volt supply also shut down? If multiple power supplies shutdown at the same time, the input power is the likely cause.
Like mentioned before, the DB-37 cable is plugged into a module (not a bumper), the Analog board that attaches to the Analog module is called a bumper.
Also when you tested it in the morning, was there new code deployed, or was it “permanent” code with no new deploying?
Also, did you test different power wires/connectors from the Power Distribution Board to the DSC?
And finally recently our robot’s wifi would decide to restart whenever I enabled the robot (happened to be for only 1 battery), but that battery’s main terminal was loose which let the robot boot fine but when it came to draw power, it crumbled. So I would check any loose connections starting with the battery. Also, test the 12V dedicated supply for the Wifi but use it on the DSC and see if it does that any more.
Hopefully I understand all of this correctly, because I haven’t seen anyone say this.
It still sounds like a short in the encoder circuit. Whether it’s wired wrong now, it’s shorting somewhere, not sure. The power shouldn’t just go out because of plugging in something unless it is shorting the power supply. Encoders are pretty dumb devices in the terms of sensors. They take in power, and give out a pulse that the cRIO counts. Plugging them into the sidecar should yield no changes at all, ever.
You should take a continuity checker, and check the black and red wire. I have a feeling that you will see 0Ω, or in other words, short circuit.
I feel that you will find that it is shorting.
I’d recommend doing the wiring again. I’d recommend YOU doing the wiring again. Only then do you know if it was a wiring fault.
Could you check the LEDs on the DSC (BAT, 5V, 6V) with the encoders attached and removed?
My current bet is either that the 5V supply is being shorted by the encoder, or that the 12V power isn’t attached correctly and the DSC is being phantom powered by the cRIO.
Bingo! Something happened during that match. A hard hit or bounce, etc.
I have seen this behavior, now that Eric mentioned the “phantom power”, I remember this during our build season.
The three LEDS might be lit, but weakly. Check the power (+12v) coming in. Maybe a bad breaker or bad connector on the PDC. Move to a new slot on the PDC and new breaker on the PDC and you may have better luck.
So after we were eliminated and went to the practice field to diagnose, everything worked fine – we plugged 'em back in to start troubleshooting and it simply worked; indeed, we couldn’t recreate the problem. This is troubling because we didn’t actually diagnose and solve the problem, so it’s far too likely that it will reappear at a particularly inconvenient time (say, Buckeye). I’m happy if it doesn’t, but don’t trust that it won’t.
A hypothesis (based on, as far as I can tell, a hunch and nothing more from one of my students talking with another mentor) is that the encoders spin so fast that they are generating too constant a high voltage signal, and that this is tripping some kind of internal breaker in the sidecar or module. I don’t even know how I’d begin to test that hypothesis, or what we could do about it if it were true – seems fishy to me anyway, as many other teams are using kit encoders on their shooters without the same problem.
Thanks so much, everyone, for taking the time to ask and answer. We’re hoping we can narrow it down fast so practice day results in a fast fix!
I’m answering all questions below; please forgive the terse tone – I’m exhausted and going to bed just as soon as I finish replying to this!
Correct.
Also correct.
Yes. We successfully used encoders last year, and they were working through weeks of testing. The wiring was double-triple-quadruple checked for continuity, shorts, and correct pin positions. DSC pins were checked for shorts.
Yes. We use some digital photoelectric sensors on our ball management system, and they’re working fine (as long as the encoders are not plugged in).
Correct – and all Victors start flashing the “no signal” flash.
Module, sorry – the DIO module has no bumper, and I know that.
Yes.
Yes.
We repeatedly verified that they are not reversed.
Only the 5V shuts down. The 6V and 12V LEDs stay bright and solid – and we can still fire relays (the compressor doesn’t run because of the pressure switch not working, but our LED ring on our camera lights up as normal. Swapping the two caused the compressor to run.).
“Run at startup” from the problem-free night before.
Yes.
Done and done and done.
I’m not sure what you mean here.
Yup, we know all that. There are no shorts anywhere that we can find, either on the encoders, the sidecar pins, or the cables.
Done and done; same problem.
Wouldn’t the latter cause a loss of functionality altogether, and not just when the encoders are plugged in? We had full pwm functionality when the encoders weren’t plugged in, and none when they were.
As to the former: that was our bet, too, but we cannot find any evidence of a short on any component.
Perhaps, though not that we recall – either way, it’s odd that the short (if it is indeed a short) seems to be undetectable by mortal (that is, 1551) means.
I saw that last year and looked for it. Our LEDs are not weak, they’re bright and strong as normal. And as I said before, we can fire Spike relays.
From your description of the diagnostic LEDs, this is an electrical problem in either the DSC or your encoder: Your 5V rail is getting shorted out. You can eliminate any theories related to software, the PD, or the cRIO.
I’m betting you have an intermittent short in your encoder wiring. This would explain why it magically fixes itself.
