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Use of Led's as Indicators

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  • Use of Led's as Indicators

    My team would like to utilize led's as indicators to help with alignment on the field. They wouldn't be anything special, just on or off and they would not be focused in any way which would make them legal by rule RE12.
    Light Sources - Light sources (including LEDs) are allowed; these may not be focused or directed in any way (for example: lasers and mirrors are not allowed).
    Given that this is legal provided that we use a legal power source, is it possible to utilize the analog or digital ports on the REV Expansion Hub to operate the lights and if so, what kind of hardware would be needed to connect the lights to the hubs? I know it is possible to achieve this using the motor controller ports, but I would like to stay away from that (we have a lot of motors already).

    Thanks, Ben

  • #2
    For non-competition (practice/debugging) purposes you can connect a Adafruit LED Sequin (available in several colors) directly to one of the 8 digital ports of the Rev Expansion Hub (connect negative to ground and positive to signal). These LEDs are designed to be controlled by the 3.3V GPIO pins of an SBC, so they are compatible with the digital [output] ports of the expansion hub.

    For competition purposes, I think the Adafruit LED Sequin could be classified as a sensor (the LED sequin illuminates when it senses 3.3V on the signal line) or otherwise classified as "null" sensor. Note that the MR touch sensor has an LED that is powered by a digital port, so it should be legal to power compatible LEDs via a digital port. Seek an offical ruling from the Game Q and A Forum if you want to connect an Adafruit LED Sequin to a digital port for competition purposes.


    • #3
      Okay thanks, I've been trying to ask some questions over there about this kind of stuff, but I haven't been able to post anything on there and haven't seen any new questions being posted which seems odd to me? Does anyone know if there is a reason for this? Or maybe I'm trying to do it wrong?


      • #4
        You cannot ask 'official' questions on your personal account, the 'team' account must be used See here for more details:


        • #5
          I believe there is an error in <RE12>. <RE12> fails to take into consideration that <RE11> allows any compatible sensor from any manufacurer to be powered and controlled by digital and I2C ports. Sensors are allowed to have light sources that are powered and controlled by digital and I2C ports.

          It is legal to use the LED on the REV, MR, and Adafruit color sensors as a status indicator during a competition. If you connect the REV, MR or Adafruit color sensors to the Adafruit I2C Multiplexer then you will not need a level shifter. Several teams have written drivers for the Adafruit I2C Multiplexer.


          • #6
            According to

            the LED on the sensor cannot be controlled by the digital pins on the hub. The example code is illegal.


            • #7
              <RE12> is nonsense... Most color sensors that teams use during competitions have a light source that is powered and controlled by a I2C port or digital port. Moreover, the MR Touch Sensor has an LED that is powered by a digital port, the MR Optical Distance Sensor has an LED that is powered by an analog port, and the MR Range Sensor has an LED that is powered by a I2C port. I doubt that a robot has ever failed inspection for using a sensor that has an LED that is powered by a digital, analog, or I2C port.