Rio Digital output - newbie help needed!

New to Rio and (relatively) new to electrical wiring – most of my world is once the I/O is in software – but loving it all so far.
I have a new Rio wired with channel 0 as a digital input on a push button, and channel 1 as an analog input on a simple pot. That works great – data’s publishing to my MQTT broker, my NodeRed is flowing, and all works as expected. However, I’m stuck on the output: I can’t make it work…

I started with an LED on channel 2, configured as digital output, but even though I see the channel change to ON (in the web UI and on my MQTT broker) nothing happens. I replaced the LED with a multimeter on Pins 7 and 8 (tried both ways), but when the Output turns on the multimeter reads no change.

Anyone have any tips for a newbie? I’ve attached a picture of how I think it should work.

Hi Jonathan. Welcome to the forums.

Glad to see you getting your hands on hardware. Im a bit the other way around, I tinker first with hardware, then get myself into trouble with the software and ask @torchard to come rescue me!

Ok I see what you are doing, but the trick is… the digital output does not supply the voltage, it switches the voltage.
So, to do what you are doing, you have two options…

  1. Get an LED power supply and wire it so the LED lights up, then break the +ve part of that circuit and put in pins 7 and 8.
  2. Change the output type of that channel in groov Manage to be a 0 to 10v analog output and wire the LED to pins 7 and 8 (Long leg on the LED is positive, or looking into the side of the LED, the large metal side is negative, or the flat side of the bottom of the led is negative). The negative leg goes to pin8.
    NOTE, if you go with option two, blasting 10v into the LED might burn it out, so you might want to scale the output in the RIO groov Manage to be something like 0 to 3v is 0 to 100%. Tip, depending on the LED you could put a currently limiting resistor in series and open up the scaling a bit, but just get it going gently at first and don’t let the magic smoke out!

That totally makes sense, I’ll try option 2 – thanks for the help!

Ben’s Option 2 idea should work on the RIO, but you will need to use channel 4-7. You might be better off using the current output verses the voltage output and sending 20mA out when you want the LED on. That is the typical max forward current for a red LED - if it is something else, then use that value.

If you use 0-10V and request 10V, it won’t actually happen - it will limit to the voltage drop of the LED (~2V) and you will see an overload message on the IO point (I think). The RIO limits the 10V output to 20mA. If using a separate voltage source and a digital output, then you will need to provide current limiting by providing a resister in series with the LED.