@dc42 said in Drive standard LEDs. What is the max current rating of IO pins?:
@o_lampe @Ralms the MCU pins that drive the IO_OUT pins on the 6HC are each rated to 4mA or more. There is a 470 ohm resistor between the MCU pin and the IO_OUT pin on the connector. So it's OK to connect an LED directly between an IO_OUT in and ground, because given the volage drop of the LED you won't get more than 4mA flowing. However, you may not get enough current to light the LED sufficiently.
When wired like this (or with the LEDs connected directly t the Duet in any other way), a short circuit between the LED pins and the 230V pins on the switch would destroy the Duet immediately.
Thank you for the clarification.
Yes, I'm perfectly aware that 230V would kill the duet, hence trying to be really careful
After some research, I've decided that I will use a daughter PCB just to deal with the switch, where the relay will be activated using something like a TRIAC Optocoupler, completely isolating AC out of the switch.
The reason I was trying to avoid this approach, was to be able to have the switch control the main power relay, without needing a second lower power DC power supply (mostly to lower standby consumption), but it would just be too risky.