pic: 3692's PDP after catching on fire at Queen City



3692’s PDP after catching on fire and making a big smoky mess out of the Queen City Regional playing field.

Could you share more info on this?

-What likely caused it
-How long it took you to fix.

Wasn’t our team so I can’t comment on it.

Making an educated guess based on the photo?

Looks to me like the positive lead of those wire stubs pulled too much current through the board (possibly by shorting to ground somewhere in the wiring between the PDP+(Speed controller of choice)), overheating it and ultimately igniting the plastic chassis of the PDP.

I will say looking at the bottom of the PDP, there was a distinct burn mark (Unfortunately I don’t have a picture) between the 40-Amp breaker slot and the smaller ones. I don’t know enough about the situation to say much more.

I do have a picture, which I will post as soon as I can figure out how to make CD allow me to. One theory was some kind of internal arcing. I’m not on their team either, but I think they’ve already contacted CrossTheRoads. The “good” news is that they only missed one match while repairing their bot.

It definitely was on fire - not just smoke. In addition to the PDP there was a bundle of CAN wire right next to the PDP that was crisped.

We are still not sure why it happened but it was definitely not something that we caused. It took us under an hour to replace the pdp, 2 talons and test everything.

So did the field’s fire extinguisher get some use?

Are you or CRE doing any analysis as to why this happened? If it was a short, the inline circuit breaker or the main breaker should have tripped (it auto resets and finally the main breaker trips), I think.

Curious to know if it the heating started on the PDP PCB (internal circuit board) somehow (possibly a metal chip that got under the cover of PDP), so the bypassed inline circuit breaker did not trip and before the main breaker (120A), tripped it melted the plastic.

Yes it did. Here’s a video of the incident straight from the stream. (we’re working on uploading the other match days- watch them on our website!)

CRE has contacted us and wants us to send them the PDP for analysis. I’m curious to see what they find and I hope they follow up with us on the cause.

It was for sure a massive short but the inline breaker and the main breaker never tripped throughout the fire. We are very careful with our electronics so I’m confident it wasnt a chip, that only leaves manufacturing defects.

Please share your/CRE findings, we all can learn from your experience.

Thanks in advance.

Good thinking on somebody’s part to have a CO2 extinguisher available rather than just standard Class ABC. That would have made a real mess.

The trouble with the self resetting breakers is that they will set there self resetting, passing enough current to feed a fire. It probably limits the current enough so the main breaker would not trip. Even 40 amps @ 12V will burn things if concentrated enough. Think car cigarette lighter for those of you with cars old enough to have them.

This was no small fire. With a 3 to 4 inch flame visible from the stands I’m worried about how the whole situation was handled. They let the fire go for just under a minute. Isn’t the main priority of first safety? Letting a fire go that long does not seem safe to me.

…or a faulty termination.
…or a jammed breaker.
…or a motor controller fault.
…or a wire with some nicked strands from stripping.
etc.

My point is that unless you have some very specific and compelling evidence to rule out everything else (or confirm it was a mfg defect) I don’t think that you should be so quick to throw CTE under the bus for this!

For example, if a few strands of one wire contacted the terminal of another wire it would take much less than 40A to heat up those strands enough to light some plastic on fire.

You’re right, I shouldn’t have been so quick to say it was an mfg defect.

It could have been a faulty 40A breaker that was not opening so save the part if you can.

My money would be on a faulty connection in the spring clamp connector in the PDP. Look into the connector with a flashlight to see if there may be some insulation in the connection area or something like that.

A high resistance joint can cause heating leading to a fire. We have had fires in the equipment we build at work when the bus bars are not bolted together tightly and 1000-2000A is put through the connection.

Did anyone at CTRE ever figure out what happened?

One thing I’m noticing is that there is no 40 amp breaker in the circuit. Could that have caused the fire? I’m sort of using my minimal electrical skills to guess so that’s why I’m asking. But they probably had a breaker in it and removed all the breakers and excess wire for the photo.