R61 or R63?

A question has come up to the legality of a switch used to momentarily disconnect a motor, to make it easier to push an arm into starting position. It would serve the same function as unplugging/plugging a connector.

Would this be allowed under R61, or forbidden under R63?

R61. Branch circuits may include intermediate elements such as COTS connectors, splices, COTS
flexible/rolling/sliding contacts, and COTS slip rings, as long as the entire electrical pathway is via
appropriately gauged/rated elements.

R63. CUSTOM CIRCUITS shall not directly alter the power pathways between the ROBOT battery, PDP,
motor controllers, relays (per R36-B), motors and actuators (per R34), pneumatic solenoid valves,
or other elements of the ROBOT control system (items explicitly mentioned in R73). Custom high
impedance voltage monitoring or low impedance current monitoring circuitry connected to the
ROBOT’S electrical system is acceptable, if the effect on the ROBOT outputs is inconsequential.

Thanks!

It seems like that would be forbidden under R63 as you’re “altering the power pathways.” However, if disconnecting your motor makes it easier to push an arm, it might be easier to turn off brake mode on your motor controller from robot code for a brief period.

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A manual switch is likely to be considered a custom circuit, and thus illegal in this application. However, connectors are legal - just put a connector in a place where it is easy to disconnect and reconnect before/after the match.

Why don’t you just unplug the motor?

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I imagine because unplugging the motor leaves the possibility that someone forgets to plug the motor back in before the match, whereas with a momentary NC switch the person has to actively be pressing the switch to disconnect the motor.

That being said, by my reading of the rules this isn’t legal. If the switch were to get pushed during the match (a non-zero possibility), you’d be altering the power pathway, not just adding a connector or monitoring device. It might be worth a Q&A, though.

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The examples given in R61 are all passive electrical items. They transmit power, but in no way alter it (aside from the obvious affects of resistance). A switch is not passive.

R63 calls out the only exceptions allowed on motor power pathways, and specifically states that the effect on the robot must be inconsequential - a switch would not have an inconsequential effect.

Connectors, like Anderson PowerPoles, are a good solution for temporarily unplugging a motor and then reconnecting it. If you would prefer not to go that route, try changing from brake to coast on the controller. If that works, some of the older speed controllers (still legal!) have that setting available using external pins and a jumper. You could hook your limit switch up to those pins in order to temporarily switch from one mode to the other.

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Thanks Jon for the rules explanation, and a possible alternative!

Also note that some of the modern motor controllers default to neutral mode once the power is turned off at the main breaker. If using one of those controllers, you may be able to work with no additional circuits required to do what you wish; hitting the main breaker will take you to neutral. (In particular, the original SPARK, but likely some others.)

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Thanks GeeTwo… I will pass this information along too!

Definitely a Q&A issue. Word the question skillfully.

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Wait, does this mean that power relays are illegal? We’re using a relay to turn on and off a light we’re using for vision tracking (not the limelight but an LED strip)

Yes, relay for LEDs is legal. We’re specfically talking about motors.

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