Have you seen Q228?

Q 228 Motor Controller (Talon/Victor) pigtail replacement.

Are we permitted to change-out the short pigtail leads on motor controller. Effectively swapping it out with identical silicone wire (same color and gauge) in order to increase its length.

Answer

No, modifications to these devices are prohibited per R73. De-soldering the wire pigtails is not one of the exceptions listed in items A-O of R73.

I would have thought this fell under R73 L and/or M, and further been usable in future years assuming that R15 D continues with little or no change. Anyone else find this strange, or expected?

R73

  • L. Integral wires on motor controllers may be cut, stripped, and/or connectorized.
  • M. Devices may be repaired, provided the performance and specifications of the device after the repair are identical to those before the repair.

R15. Physical ROBOT elements created before Kickoff are not permitted. Exceptions are:

  • A. OPERATOR CONSOLE,
  • B. BUMPERS (a protective assembly designed to attach to the exterior of the ROBOT and constructed as specified in the BUMPER Rules section),
  • C. battery assemblies per R5-B,
  • D. FABRICATED ITEMS consisting of one COTS electrical device (e.g. a motor or motor controller) and attached COMPONENTS associated with any of the following modifications:
    • i. wires modified to facilitate connection to a ROBOT (including removal of existing connectors)
    • ii. connectors and any materials to secure and insulate those connectors added
    • iii. motor shafts modified and/or gears, pulleys, or sprockets added
    • iv. motors modified with a filtering capacitor as described in the Blue Box below R63

I thought it was weird at first, but I think the key part making it illegal is soldering in longer wires. If the wires were the same length, it would count as a repair.

Then… would soldering or butt-splicing on additional wire length to the ends of the factory wires also be illegal?

I would assume butt splices count as a “connector”, but you bring up a good point about soldering. I guess this is one for the next team update…

From my interpratation of it, because you would be fitting the motor controller with a new/additional pupose (being able to have it be farther away without normal connectors) it wouldnt qualify under a repair as it would not be identical (and it wouldnt fall under just changing the wires as you are technically messing with the circuit board as well). While “connectorizing” (in which ever fasion you choose) the end of the original cables to increase length would be legal under the R73 exceptions

OK, let me point out the slippery slope here. How short may the factory cable become before this shifts from being a soldered extension to a factory wire to becoming something ELSE? One inch? One millimeter? Ten microns? One angstrom? Zero?

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I’d say once it becomes an “Unusable” length. If that’s being that you cant get a connector on, or what not I’d say that’s up to your interpretation. As long as you don’t make it longer than the Original factory length, you should be fine. If you make it obviously longer than the original specification you might run into trouble with an LRI, but I doubt it.

Edit: To be clear with my other reply, your original question makes it sound like you want to extend the wires from being the factory length to much longer than that. Whether it be to not worry about a loose connector between the ESC and PDB or what not. Which would not be covered under the R17 or R15.

I suspect it may be related to the opening of the case… or more specifically the modification taking place inside the case.

I see your argument, however “cut, stripped and/or connectorized” doesn’t include “lengthened”, and repair both requires the device to identical and implies that the controller had been damaged. Lengthening the wire of an undamaged controller is not a ‘repair’.

Were there not a Q&A to the contrary, I think 15.D.i could have reasonably been used to argue that the wires were “modified to facilitate connection” as the type of modification was not defined, but now that the Q&A exists we have some definition.

As for the minimum length of original wire, I think you should be safe so long as the connection can be inspected when the speed controller is closed up and ready-to-go.

The Q&A ruling may be related to allowing inspectors to inspect the connections to the motor controllers and/or ensuring that teams are able to replace their controllers should the need arise.

Or it may be the rule because its the rule. :slight_smile: Either way, I think it is fair to say “don’t make changes inside the magic black boxes”.

Jason

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Even though the ruling may actually disagree with the rules as written, I think it’s the right one nonetheless.

The power wires in sealed motor controllers like the Talon SRX or Victor SPX are very close together, and can carry huge currents. While I might be okay with mentors or other professionals making the repair, I certainly wouldn’t want a student on my local rookie team doing it without fully understanding how to. That’s a good way to get electrical fires at competition. FIRST has no way of ensuring the people making the repairs are properly trained, so they were right to outlaw repairs altogether.

If you accidentally cut your wires too short to the point where they’re unusable, send an email to CTRE customer support. They’re generally very helpful, and may offer to repair it for you for less than the price of buying a new one.

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Based on the way they changed the CAW rules this year HQ obviously has no interest in making logical decisions that make this program cheaper for teams. It seems they want you buying brand new stuff every year.

Have you tried listing all of the COTS suppliers as team members? It saved us thousands on our BOM.

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Our newest mentors are Ken, Jeff, and Andy.

They are a little shifty but they assure me that everything they are teaching our students about the BOM is very legal and very cool.

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The way R73 is written repairing is legal, so you always can return it to original supplied length via replacing the pigtail. However, by the same rule you cannot change the specs by using a longer length of wire. R15 just allows you to remove the connectors the COTs item came with.

I think the key point is that you can remove COTs connectors, and/or cut pigtails shorter. You cannot rewire COTs, to make the pigtails longer. There is no conflict within the rules.

Yes this is stupid as it would be very useful to have a bunch of motor controllers with much longer pigtails on them. We use the mini Anderson style connectors, and the connectors often end up in an unfortunate place on the mechanism. Plus we try and design mechanisms that are replaceable which requires a second set of connectors at the interface point.

Did you put the law firm of Dewey, Cheetham, and Howe on retainer?

My personal prediction: this one gets clarified or reversed. And personally, if they haven’t cracked the motor controller open I really don’t care. (And even if they did, it may still be okay but merits more scrutiny.)

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Maybe I’m misunderstanding the original question, but doesn’t replacing the wires on a Talon SRX or Victor SPX require opening the motor controller case, de-soldering the old leads, and soldering on new leads? If you can make the repair without all of that, then that’s great and should probably be legal. I’m fairly sure it’s not possible though.

Motor controllers can be dangerous if faulty, and I don’t think FIRST should be in the business of having teams trying to fix them themselves. Really, I think R73 is too permissive as it. Well-meaning students can seriously hurt themselves and others if they don’t know what they are doing while trying to repair their electronics. Allowing teams to save bit of money isn’t worth the possibility of students hurting themselves. In my mind, R73M should allow for opening the case of electronic devices to clean them, but no other modifications (e.g. soldering, disassembling, etc).

I understand this decision. Why would you be able to open up a speed controller, desolder some components, and replace them with your own? That seems a little ridiculous.

You need to join your extended leads to the existing leads. Seems pretty straightforward to me. That’s still plenty legal.

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No retainer needed, that firm works pro bono pro tenebris.

+1 on the idea that motor controllers should not be opened up für fingerpoken und mittengraben bei dem Dummkopfen.

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Modifying any electrical component increases the chance it turns into a thermal component.

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Very true. However the most likely failure mode of the new controllers is capacitor failure after being reverse biased. Opening and changing is a very simple repair.Said repair is well within the competencies of many/most teams.

We earmark such repaired controllers for the practice bot, as a derisking measure, so they would not be seen by a RI or LRI anyways. However, this type of repair is much simpler than the expertise required to craft legal CUSTOM CIRCUITS, so I don’t understand the angst being expressed.