R611 Change?

The 2023 Game Manual changed R611 to require a 120Ω resistance between the robot and the + and - posts of the APP connector (2022 required 3kΩ). Would it be possible to “exploit” this change by connecting 120Ω resistors to the + and - posts of the APP connector and using the robot frame as a wire?
However, you wouldn’t be able to do much because your maximum current would be 12V/>240Ω = <5 mA.

I believe it calls out a minimum of 120 ohms of a leakage path to the frame in order to minimize current in the frame. In a perfect world the resistance to frame will be much higher. There should be no intentional electrical connection to the frame.


Even if R611 would “technically” allow using the frame as a wire, doing so intentionally would be a clear violation of R203, as the current in the frame would be “causing an unsafe condition” and thereby violate the blanket safety rules.


I don’t see any way that one could consider 5mA at 12v or less unsafe. But even if by some backwards logic it was deemed to be unsafe, it would still be deemed illegal if it was noticed by the inspector as the rule clearly states

R611 *The ROBOT frame is not a wire. All wiring and electrical devices shall be electrically isolated from the ROBOT frame. The ROBOT frame must not be used to carry electrical current.

As I read it, even if it doesn’t exceed the 120 ohm limit. Intentionally passing current through the frame would be illegal as Blue boxes

do not carry the weight of the actual rule (if there is an inadvertent conflict between a rule and its blue box, the rule supersedes the language in the blue box).

and the 120 ohm limit is there simply to allow for minor weak, unintentional connections


Question 182 has been answered, stating:

Yes, Compliance with R611 is checked by observing a >120Ω resistance between either the (+) or (-) post within the APP connector that is attached to the PDP/PDH and any point on the ROBOT. Teams can view the Electrical Inspection Video for an overview of how this is checked at an event.

This implies to me that only the resistance is checked, not whether current is actually being carried (intentionally or not).

Well, there’s no good/easy way to check whether current is being carried in an inspection checklist, so the resistance check is a proxy for the actual rule as an easy way to check for the most obvious/common violations. Not all rules are directly inspectable, but they should still be followed (e.g. per the rule, the chassis should not be used to carry current, even if the test called out in the inspection checklist might not “catch” it).

Note: the resistance requirement used to be 3K ohms, but a lot of newer devices aren’t quite as insulative (e.g. they might have ~10K ohms, but not >100K ohms, between the case and electrical ground) and enough of them in parallel could cause false positives, so the resistance limit was relaxed to reduce false positives.

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I don’t think this requirement is for safety. I believe it is to reduce the likelihood that a robot sits dead on the field or does “unexplained things”. There is usually several threads each year where someone is having a problem, the wiring and program looks good and it is eventually found that some component was shorting to its case and to the chassis.

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I suppose, one might be able to ask Q&A something along the lines of, “Is it a violation of R611 to intentionally use the robot frame to carry current, as long as there is always at least 120 ohms between any point on the frame and the APP connector?”

But it may be a better use of one’s time to just design your robot to not use the frame as a conductor, rather than trying to find how close to this rule one can push. :slight_smile:

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I’ll agree with half of this. Having the chassis carrying current is a safety thing, and 120 ohms is going to keep the current to less than 100mA, which isn’t likely to be an unsafe condition. On the other hand, when I was mentoring a team, we would continue to trouble shoot this until we were over 1Mohm, for “not moving and other unexplained things”

I am coming from the perspective of safety of the people. The various electrical safety standards allow the equipment being test/evaluated to be destroyed as long as no unsafe conditions are created (greater than 50V on the enclosure, emissions of flame, flying debris etc.)

Limiting the fault current may save the equipment (robot) but only if the fault impedance does not decrease. Since this impedance is due to some fault in a component, one cannot expect it to stay constant. It may “burn open” or it may become a dead-short.

Q182 doesn’t address this. It confirms the testing criterion, but doesn’t offer any additional insight.