2Pcs PC817 8 Channel Optocoupler Isolation Board 3.6-30V Driver Photoelectric Isolated Module Voltage Converter Adapter Module

I often need to isolate circuits with different voltages. My last project interfaced 5VDC to 12VDC. These boards did the trick very well. I like the individual boards (instead of a single board with many optoisolators) , because I don't want to connect the Grounds of the inputs or outputs. The boards do contain jumpers for ground, but don't eliminate all the common grounding. Having multiple 2 channel boards allows me to do this fairly easily.The drawback is the multiple boards & wires laying on the desktop - but that's a minor issue. If you incorporate these boards into a final project, they take quite a bit of real estate. The optoisolators themselves are typical 817C IC's paired with a few 3K current limiting resistors and an LED that can be had for less that $2.00 total. Nevertheless, this card makes it easy to prototype, and construct simple isolation circuits.

A very compact PC817 PCB design. The jumper allows for isolation between in/out. See schematic I came up with for it.