Wire Color Woes

FIRST General Forum
#1

So last year <R41> stated:
All active PD Board branch circuit wiring with a constant polarity (i.e., except for relay module, speed controller, or sensor outputs) shall be color-coded as follows:
A. Use red, white, brown, or black with stripe wire for +24 Vdc, +12 Vdc and +5 Vdc connections.
B. Use black or blue wire for common (-) connections.

Can someone explain to me why they care? Our team just got offered a large quantity of purple and teal automotive wire, and while ugly, it would be free, thankfully our electrical lead informed me of this rule, and I have to say I am rather frustrated at this… Help please? Would your robot be disqualified for incorrect color wiring?!?:yikes:

#2

There are several reasons why this is important, but I think the biggest is that it makes the Inspection process move as quickly as possible.

It’s best to assume that it would.

#3

Your robot would not be disqualified if these wires were in place. However, you would simply not pass inspection until the wires were replaced with wires that adhered to inspection rules. So, the inspectors would inform you of this and then pass you once the wires were replaced.

Andy B.

#4

It’s a sad thing indeed. We were given a couple spools of purple wire, and given our team color it would have been cool to use… Alas, not legal.

I understand completely why, though. Having to inspect these kitbashed monstrosities we call robots is an arduous task. The more standardization you can make, the easier it becomes.

#5

Don’t lose faith. This wire can absolutely be used for prototyping, offseason activities, a practice robot, or restraining hyperactive freshmen.

What gauge is the wire?

#6

nn,
The wire related sections used in the Robot rules is meant to follow the NEC (National Electrical Code) and IEC (International Electrotechnical Commission) specifications for wiring. We adhere to these standards to allow our students to learn conventions used in industry while also simplifying the inspection process and making it easier to diagnose problems.

#7

Also note that the wire color guidelines for the robots aren’t arbitrary - they didn’t just pick random colors for + and -. Those colors are standardized, and you’ll find them like that in everything from your house (typically white/black) to your stereo (typically black/black stripe) to the innards of your computer. Yes, FIRST is focused on inspiration, but that doesn’t mean we ignore education. By introducing these wire guidelines while working on the robot, you are better prepared to recognize and use them for the rest of your life, whether you’re wiring some speakers, installing a new lighting fixture, or actually working as an electrical engineer.

#8

Thank you all for your input, I was frustrated in that moment, but I now see the value. Still think that black and purple wiring would have been cool, and easy to follow… But alas the rules.
Thanks again for the input,
Nathan

#9

You might note that those color requirements only apply to wiring with constant polarity (e.g. between the PD and a jag), so you are free to use purple wire to your heart’s content on the output of jags and relays, which has the added benefit of acting as a quick reminder that the wires are not constant polarity.

#10

Exactly what I was going to propose.

We’ve debated doing something similar for a while (red/black for constant polarity power distribution, and something else to the motors). We decided not to so we don’t have to stock more wire.

However, if you have the wire and want to use it, it’s a great choice.

#11

That is certainly legal. I would strongly recommend, however, maintaining some sort of standard on the outputs of your relays and speed controllers. Every relay and speed controller has a labeled positive and negative, even though the polarity may change. Likewise, most of the motors we use have indicated positive and negative terminals. The combination of the two allows for easy wiring of motors that have to work together.

For example, if you have 2 CIM’s going into a Tough Box, hooking the red’s to the positive output of two Jaguars, and the blacks to the negative, you know that setting the Jaguars to the same value will spin the CIM motors the same - there’s no trial and error where you don’t know which way each motor will spin.

By maintaining some standard (for example, purple is always attached to the negative output from a speed controller, and teal always to the positive), you can possibly save your team some headaches if you burn out a motor and need to do a fast replacement between matches.

#12

This is a good point that I should have mentioned in my first post. We do something similar, we only use red/black wire for our robot (less stock to maintain), but we use red/black powerpoles for constant polarity connections (including devices that we always want to run the same way and compressors) and white/blue powerpoles for connections with non-constant polarity.

#13