Limit switch wiring question

**I am trying to find the ruling on the wire used for limit switches. **

I have some cable that contains red both & black 22 AWG wires that I would like to use but
I am not sure if this is allowed because of how the following 2 rules could be interpreted.

Can I get a consensus on this?

  1. Per R59, Do limit switches fall under the category of SIGNAL LEVEL circuits?

  2. Per R61, If these limit switches are considered non-SIGNAL LEVEL wiring, and there really
    isn’t a constant polarity for these, do I need to have individual colored wires the total length
    or can I use my grey cable?

  3. Anything else in the rules that would limit the use of this cable?


Under R59:
SIGNAL LEVEL circuits (i.e. circuits which draw ≤1A continuous and have a source incapable
of delivering >1A, including but not limited to roboRIO non-PWM outputs, CAN signals, PCM
Solenoid outputs, VRM 500mA outputs and Arduino outputs) 28 AWG (29 SWG or .08 mm2)

Under R61:
All non-SIGNAL LEVEL wiring with a constant polarity (i.e., except for outputs of relay modules,
motor controllers, or sensors) shall be color-coded along their entire length from the
manufacturer as follow:

A. Red, yellow, white, brown, or black-with-stripe on the positive (e.g. +24VDC, +12VDC, +5VDC, etc.)
connections B. Black or blue for the common or negative side (-) of the connections.

It’s SIGNAL LEVEL wiring, so doesn’t matter what color it is. The roborio doesn’t deliver 1A across its signalling lines (according to the specs, it can only deliver a total of 1A across all the +5V lines. In reality, you’ll get a few milliamps.) If you’re plugging directly into a motor controller, you’d have to look at the specs for that controller, but I’d be REALLY surprised if any of them pumped more than an amp of current through a limit switch.

That said, using red and black cable for something other than power might confuse a robot inspector. If it were me, I’d use something else.

If you’re connecting the limit switches to the DIO ports or the limit switch terminals on a motor controller, then yes, it’s signal level wiring. The signal wire is not “constant polarity”, but the ground line (and 5V line if used) are. Even though the color code isn’t mandatory for signal level, it makes things much easier to identify and understand. We usually use PWM wires in appropriate colors for our limit switches.

We use a 24-2 stranded cable for our limit switch wiring, something like this. It has two conductors in a grey sheath. No one is confused by it.

Stranded is highly preferred over solid for reliability reasons.

Thank you MrRoboSteve

That is what I have and wanted to use.

So you have used this for limit switches that connect to the DIO and have not had any problems with the inspections?

Hasn’t been a problem for us.

Thanks CEF

I usually place a wire wrap label on each end of my cables to save headaches down the road…

We use this

thanks for the tip

I have access to a cable label printer so I can place descriptive info on the labels like “to DIO-0” or “From Arm top limit switch” or actual signal names…

As long as the outer sheaf is marked with the gauge wire, that should be good.