Robot reboot often, faulty PDP?

Technical
1

We have this problem in the crescendo season, where our robot reboots when it has a slight impact from other robots or any structure.

At any impact to the robot, it reboots instantly, and we lose the connection.

We first thought it was some cabling issues, but after checking the controllers and cables, we concluded it might be a different problem.

We tested It out with different radios, roboRIO, etc. But only when we changed the PDP, did the robot stop rebooting.

Somebody has gone through this problem? Does anyone know the solution to this?

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2

Check your strip length on the main power connections; its crazy long, and if its too short you get iffy connections!

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Thanks for replying, indeed our cables for main supply from the battery have a big length difference, let me correct that and check if it works.

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Are you using a PDP or a PDH? Since you said PDP, I’ll assume that is what you actually have.

Some possibilities include:

  • Bad or loose fuse for the controller output on the PDP.
  • Poor power termination at either the PDP or the Rio. Are you using ferrules on either or both ends? If the wires are bare are they clean and nicely twisted? Oxidized or crumpled connections are bad connections. The Sauro connector on the Rio is notoriously hard to get a good tight connection on; if you can, consider replacing it with one of these.
  • Loose main connection to the PDP - check your crimps and make sure the ring terminals on the inputs are tightly bolted down.
  • Worn out Weidmuller connector on the PDP.
  • An internal failure in your PDP.
  • A break inside one of the power wires you’re using. This is rare but possible if the wire has been stressed or fatigued excessively.

If you’re using a PDH, then as noted above you should also check strip length on your main power leads (they need a full 3/4" stripped from the ends to engage properly) as well as the strip length on the power wires going to the Rio from the fused channel you’re using to power it.

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We actually had a problem where the robot would randomly die during matches, while we were just driving in open field. Like this one: https://www.youtube.com/watch?v=ndBrHb8vJyM&t=79s (2832, far right)

We traced it to a bad main breaker. It just would die randomly at times that weren’t high draw scenarios. We changed the main breaker after 2-3 of these events at the district, and haven’t touched it since (6 more events played). We have never seen these main breakers fail in years, but this one was just bad.

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Was it by any chance an Optifuse breaker? Those have a reputation for several kinds of unfortunate failure modes.

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By checking so do you mean wiggling, pull testing and/or reconnecting?

Are you losing connection to the roborio or is the radio/wifi going down?

Also how old/used is/was the PDP?

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I think you kinda missed the point there. Look at how much insulation you stripped from your main power wires going into the PDP. If you didn’t strip enough, you might be getting intermittent connections. @weldingrod1 's point was that you need to strip more insulation than you think you need to.

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Oh, thanks for clearing my doubts. I didn´t even think about that. Im going to check that.

thanks for replying!

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Thanks for replying such a complete answer, we’re currently using a PDP from 2018. I’m going to check all of these and see if any of it was the problem.

Greetings!

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Unfortunately, the problm it wasn’t our battery breaker, as I see. We changed 3 times to different breakers and still we had the problem :frowning:

Thanks for replying!

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It was a bussmann. We actually tried it on a bench later and it was tripping well before the 120A it was designed for.

We’ve probably used 15 of these through the years, and they have been super reliable. We’re planning on keeping using them. Just one random bad one.

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We reconnect all of the cables and re-wired all of the electronics, including the pulling and jiggling too.

The connection of the radio goes down. It’s like the radio is rebooting real quick.

Our PDP is from 2018, we didn’t have enough money to buy another one. Hopefully in this week, we’re planning to order a new PDH.

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How are you powering the radio? What is the power path from the battery to the radio? There are a lot of instances of faulty POE injectors over the years, etc.

(I will assume the old radios for the moment, not the new VH ones. )

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We use a PoE cable connected to the VRM. We changed the PoE cable and the radio itself and the problem continues… :frowning:

Thanks for replying! Might change that too again.

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Did you check the seating of the radio fuse? If it’s not in there tight it might wiggle a bit on hard hits.

17

Oh. Have you modded the radio to deal with the ground plane issue?

See OM5P-AC Radio Modification — FIRST Robotics Competition documentation

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Thanks for replying!

We´re just going to do this and see if it was the problem. Im going to update you for this :slight_smile:

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Thanks for replying!

We havenot modded yet the radio, I’m going to do that real quick and update you. :slight_smile:

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A few general things here…

  1. Start by assuming there’s one wiring error and try to trace it down. There might be multiple, but it’s easier to think about it if you assume one to start.
  2. If multiple components are simultaneously going through a full reboot cycle, catalog the set of components. Look for issues in connections that are common to feeding all of them. Don’t waste time looking for issues that don’t explain all the reboots.
  3. Practice the 10-lbs tug test. A connection that can’t survive a 10-lbs tug won’t survive in competition either.