Need help regarding competition legality

[SpaceKake]

I was at a game just yesterday and I was using the motor controller 29 parts to just turn on 2 led strip lights on my robot(there are 3 controllers and a strip light on the bottom and top)

The lights are just set to turn to a specific color when started and they do nothing else but act as decoration. When me and my team where getting our bot inspected one of the inspectors said that it was fine but some judges might tell us to take them off. I was concerned about this because in the inspection checklist it states that you can use non vex parts for non functional decoration.

He never made it fully clear if it was allowed or not. Any help on the subject is appreciated

[jpearman]

Not sure if a Q&A has been asked this year, but last year use of MC29 was ruled illegal.
https://www.robotevents.com/VRC/2021-2022/QA/942

MC29 is also not on the list of allowed electronics from the cortex system.

[turbodog]

Isn’t the 393 controller needed for the flashlight accessory? Or are both of these illegal now?

[SpaceKake]

So would it be perfectly fine if used them without the motor controllers and directly to the three wired port to just use them as the led object

[teresajude]

Actually, the MC29 is on the list of specifically prohibited electronics from the cortex system.

If you look in the Game Manual, specifically under <R6> (page 41 in revision 2.3):

@Spin-Up Game Manual (v2.3) <R6>

b. The following electronics from the VEX Cortex control system are not permitted:

(additional line items omitted)

SKU: 276-2193
Description: Motor Controller 29

Sorry, but I don’t think that is legal.

[technik3k]

@SpaceKake, regardless of the legality of the MC29 controllers as the part of non-functional decoration, you may want to change you connections to make it safer.

By connecting negative outputs of MC29 controllers together you make it one programming error away from shorting 3-wire power rail to the ground and damaging either MC29s, V5 power rail, or both.

Please, take a look at the alternative (safer) schematics discussed a few years ago here:

[Tutorial] Programmable RGB Lights With VEX V5

Thanks @technik3k. Jpearman did say “there is current limiting on the 5V output” (of the brain), so I think the hardware would forgive a non-prolonged short while testing. I totally agree, however, that shorting should be avoided by using a circuit where software cannot cause one especially since this tutorial is aimed towards the wider vex student group who are probably less careful and knowledgeable about the risks. My previous comments had a few errors. One of those is my assumption that th…

[teresajude]

@technik3k

@SpaceKake, regardless of the legality of the MC29 controllers as the part of non-functional decoration, you may want to change you connections to make it safer.

By connecting negative outputs of MC29 controllers together you make it one programming error away from shorting 3-wire power rail to the ground and damaging either MC29s, V5 power rail, or both.

Please, take a look at the alternative (safer) schematics discussed a few years ago here:

[Tutorial] Programmable RGB Lights With VEX V5 - #19 by matthewb

VERY good point.

Remember, the MC29 controller is designed to be able to run a 393 motor forwards AND BACKWARDS.

As a result, it almost certainly uses an H-Bridge controller.

I would never recommend wiring multiple MC29 controllers in parallel. If you set one to run forwards and the other to run backwards you have effectively shorted 5V to ground (as mentioned).