NOYITO 1-Channel PC817 Optocoupler Isolation Module Optoelectronic Isolator Signal Isolation and Anti-Interference 3-5V 12V 24V (Pack of 2) (12V)

They work as expected and have an led light that glows when active, which is nice for debugging. I used it to convert a 12 volt sensor signal to 3.3v pico GPIO input

These are still being tested, but so far they do exactly what they were designed to do. The wire clamps are a little tight but I'm using solid core wire so it is not an issue for me. I did try it with multi strand 18 gauge wire and it fought me a little keeping the strands together. Could easily solve the issue with multi strand wire by using ferrule crimps.

Excellent quality overall. Worked as advertised. The 12V variant pulls 2.3 mA on the input side (the resistor is 4.7kOhm plus there is a red LED in the input path). The resister therefore has to burn 25 milliwatt which is fine. The other variants will probably also draw 2.3 mA und burn off less power. If the output is tied to an input that has an internal pull-up, one can just use the output pin and the output GND. The VCC can stay unconnected.

Perfect. Worked great for my project and kept it simple

I bought 20 of these to interface a Nayex credit card reader to a car wash. The card reader would output a 5V signal and the car wash required pulling a 12 volt line to ground. To make it reliable, I had to replace the input resistor with a smaller value. I think it was a 1k and I replaced it with a 220 ohm resistor. The resistor value needed depends on the output current required. I expected I'd need to modify it when I bought it. It was easy to modify and all 20 of them have been working perfectly for a year now.

both of them had rusted screw terminals right out of the box

Works well - as described

Datasheet for a PC817 doesn't match this optocoupler, which is for a TLP785.