Main Power Switch Wiring and insulating?

Last season, we had an issue where our robot would randomly turn off during a match. We traced the issue to our main power switch amd the wiring bing loose (the cable had come out of the ring connector crimp). But upon further investigation, there were other failure points in our wiring to and from the switch.

We have typically used cheap aluminum ring connectors, and this is what caused the crimp to wiggle loose after an extra long season.

We also struggle with insulation on that device. We usually just use electrical tape, but it frequently turns into a huge tape ball.

So, what connectors do you all use for the main switch, and how do you insulate them?

I did look around, but have not found too many resources. I must be missing something as this is arguably one of the most vital pieces of the robot safety and operations.

We usually just use the normal crimps, but make sure you can actually crimp them correctly. Harbor freight sells a hydraulic crimper (https://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html) that works fantastic for doing this. You can actually get a solid crimp with this. For 6 awg, it’s basically impossible to get a crimp without hydraulics.

If you use heat shrink right up to the ring, you can usually get away with just a strip ofr 2 of electrical tape, as most of the metal will be insulated already by the heat shrink.

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Thanks. When you say normal crimps, do you moan those for the batteries like in the Spectrum guide, or do you use different ones?

Yes, the same ones for the battery work.

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Link to the Spectrum guide for other readers:

Highlighting this line of the document because I find it to be important:

¼-28 Studs switch the nuts to ¼-28 nylon lock nuts

A couple things I’d add:

  • You could also use nordlocks here if you wish
  • The product cutsheet gives a torque spec for the studs, ideally you’d honor that (you’ll want a small torque wrench)
  • We have often insulated the posts with paint-on liquid insulation, this is messy and gross but you can always clean it up later after it dries

(@AllenGregoryIV I can develop these suggestions further if you think they’d be worth adding)

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Linerless self vulcanizing tape is really nice for insulating weird shaped things and stuff you can’t slip heat shrink on. Its used for high voltage splices and, oddly enough, is usually on the shelf at Home Despot. Its also good for strain reliefs and grippy robot rollers. It ONLY sticks to itself, so its possible to cut it back off without leaving a goopy connection (like that horrid vinyl electrical tape). Follow the instructions; you MUST stretch it to make it work right!

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This is a much better solution than the one I had developed for wrapping electrical tape completely around the battery terminal with the lug, screw and nut. It required the use of a thin implement like a small Allen key to get the tape into the small space between the terminal and the parts of the battery surrounding it. It was time-consuming and awkward and difficult to teach.

Do you mean the Bussman catalog for the breakers? I haven’t been able to find a torque spec there.

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I have gotten good 6AWG crimps for lugs and SB-50’s using this inexpensive manual tool: https://www.amazon.com/IWISS-Terminal-Crimping-6-50mm²-Electrician/dp/B017S9EINA; they’re not the prettiest on the outside, but I haven’t been able to pull them out, and they haven’t gotten any warmer than the wire in my experience. I prefer copper lugs; if it’s required for the wire, why not use it for the connections?

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Thank you. Do you have any lead on good copper lugs?

This document linked from the AM product page gives a torque spec of 50 in*lbf.
am-0282_data_sheet.pdf (156.4 KB)

The ones linked from the Spectrum guide are copper; am-0805 are also copper. (I’m not sure what G2 is talking about.) These things look silver in color because they’re tin plated as an anti-corrosion measure. The thin layer of tin doesn’t measurably affect the conductivity.

As long as you’re using a crimper to match, lugs of this style are the best choice for your robot.

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Please note note that the complete spec is “Torque Rating: 50 in-lbs (5.6N•m) max”. this means that the studs will survive torque applied to them of up to that value. The manufacturer does not guarantee that it will survive torque above that figure. In other words, it is a maximum limit, not a target.

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Thank you. I did not know those were copper. That is exactly what I was looking for.

I use this torque wrench for my bike, and it works a treat. You would need an adapter, but it works well. It is 28 dollars and small enough to fit in my tool roll. This is both smaller and cheaper than many I have seen. I have not cracked or seized any components, so I assume the gauge is somewhat accurate.

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