Wiring LEDs into the control system/motor controllers

 With this year's game in mind, my team is looking at using small single LEDs to light up various components on our robot. We have had trouble running multiple functions on our Arduino at once (randomized led fading and led strip program). Since this has not been working we are looking into other methods or powering this LEDs. 
 With regard to rules in the past, would it be possible to wire individual LEDs to each motor controller output, with a motor attached as well? This way we should see a dimming effect when powering that motor. We are not sure if this rule (R53), or others prohibits this.

"R53 Each power regulating device may control electrical loads per Table 4-4. Unless otherwise noted, each power regulating device shall control one and only one electrical load. (2016 FRC Game Manual, firstinspires.org).

 Would it make more sense to use a relay? Also, where would we find/buy a relay and what type should we purchase, if necessary?

2nd part of R53:
*Multiple low-load, pneumatic solenoid valves, electric solenoids or CUSTOM CIRCUITS may be connected to a single relay module. This would allow one (1) relay module to drive multiple pneumatic actions or multiple CUSTOM CIRCUITS. No other electrical load can be connected to a
relay module used in this manner."
(2016 FRC Game Manual, firstinspires.org).

 If there are any other strategies that we should approach, or any comments/concerns please feel free to let us know.

    Thank you,
        FRC Team 2906
        President Walker Ward

First up it is illegal to run something such as LED’s in parallel from the Motor Controller Output. Even if it wasn’t they wouldn’t light up at all when Motor isn’t being drive and would be very dim most of the time depending on the Duty Cycle of the output. Also the LED’s would actually be the brightest when the motor is at fully power( 100% duty cycle) rather than the dimmest. They would also probably not appreciate the Pulse Width Modulation and die.

If you are using single LED’s rather than strips the LED’s are probably quite high in power( and thus draw a lot of current) so you will most likely need to use a Spike Relay.

You can use the Solenoid Outputs on the PCM as these are basically inbuilt little “relays”(solid state) which then control the main solenoid which shuts/opens the air flow. But you need to be careful and each port on the PCM can’t supply a lot of current and you risk blowing the fuse on the PCM which will mean no pneumatics.

If you really mean single **SMALL **LEDs, you may be able to power them directly from the DIO ports (check the current requirements of the LEDs and the current providing capacity of the ports), and you could program some duty cycle dimming in your periodic functions for them. If you have a higher current draw requirement but are willing to give up on the dimming, you could use small 5V or 12V relay modules, switched from DIO or relay ports.

The PCM is an option for powering 12V LEDs. Note the 500mA aggregate limit on current for the solenoid ports.

This is another way to wire leds on the robot. there are tutorials on their site how to wire and contol them. http://www.mindsensors.com/frc/181-canlight-led-strip-controller-kit-for-frc-robots

Robot rules do not allow LEDs to be attached at the output of the speed controllers, sorry. There are other issues that actually make this impractical. The output polarity of the controller changes with direction which would require either two LEDs (one for each polarity) or a bridge rectifier (difficult to do correctly) to allow the LED to respond to either direction. The LEDs will not be visible during normal competition and as others have said, the brightness of the LED will vary depending on the output PWM duty cycle. However, if you are intent on knowing the output of each controller, robot rules have allowed for low impedance current monitoring for many years. Many of the controllers actually provide this info on the CAN buss when you use it. That feedback can be used to control LED drivers through software and legal hardware.

In 2016, 548 planned on having Led strips in the DT controlled by an Arduino that received talon setpoint info over i2c to basically emulate the talon status light.