Input optoisolated with PC817

[MATHEUS G]

Hi I'm developing a board to isolate external GPIO signals from a Nordic nRF52832 (Isolated input from 5VDC to 25VDC).

For this I am using a circuit with the PC817 optoisolator, like this:

my doubt is:

Knowing that my input can vary from 5 to 25VDC, how can I indicate the activation of this input with an LED? I would like that every time there was a pulse (HIGH) in the input, the led would light up.

What's the best way to do this?

[Kenneth]

Hello,

This forum is mainly for development on the nRF platform.

But my 5 cent, you can for instance place a LED in series with a small resistor (e.g. 10ohm), this can be placed in parallell with the 10k ohm pull up you see in your figure, then every time there is voltage on the input the LED will turn ON. Alternatively you can just control an LED (through a transistor) from a different pin of the nRF52, so every time IN_1 go low you also turn ON the LED from the MCU using this pin.

Kenneth

[MATHEUS G]

Thanks Kenneth, the transistor idea is great.