Forgive me, I know this comes up often as I have tried searching both on the forum and on the web...
I am in need of isolating digital inputs, for example I want to use a photo sensor (break beam) which has 10-30V signal (I'll be powering at 12VDC). I know I can buy the components and figure something on my own but I'm looking for an off the shelf unit that is low cost with several isolated channels. There will also be some pretty high power near by (I think around 7,000 volts) so I need to protect from noise as well. I was surprised to not find a shield that could do this for me in the 12-24V range. Did I miss something? What are others doing? I found a DIN rail unit at automation direct that has 4 channels for $65 but that is too rich for my budget.
For a sensor whose output voltage is too high, a simple voltage divider is sufficient to drop the voltage to a usable level. Even at Rat Shack's retail prices, that's only 30 cents.
If the distance from the sensor to the Arduino is minimized, so will the potential for interference/noise.
I was hoping to find a prebuilt assembly that can handle a few channels of input rather than making my own circuit. Does such a device exist at relatively low cost?
If the inputs are 24V doorbell, HVAC or garage-door type signals, then you also have the option of using the signal to close a small relay and have the contacts wired up to a digital input.