I am building a circuit to read atleast 22 input channels (24 vdc) using an Arduino board which essentially works on 3.3 vdc or 5 vdc.
My current setup makes use of 22 PC817 optocoupler. I am sharing the most basic circuit diagram below with only one channel reading capability to keep it simple to understand.
To drop the voltage and keep the optocoupler safe, I've used a voltage divider with a 68K and 1.5K Resistance (±5%/±10% tolerance) that would drop the voltage to around 3.3 vdc, that I think would be safe for PC817 (please correct if I'm wrong).
Now since there are 22 channels to read, using 22 x PC817, 22 x 68K and 22 x 1.5K resistance adds a lot of complexity to the circuit, I wanted to know if there's a better way to do it.
I read about 8 channels Digital Isolators like Si838x, and have following questions:
- From what I understand I can feed 24 vdc directly to this IC and will be able to handle?
- If not, is there any other alternative to this digital isolator were I can handle preferably more channels on one IC?
- If it is a no for both 1 and 2 above, what are the best options I have for a multi-channel Opto-coupler?
- Any other suggestions to keep the final circuit small?