It depends on the optical sensors you use.
If you use just the optical sensor, that's a bit trickier, but to use something like this:
[www.ebay.com]
You can almost just plug them right in and work.
Some have the sensor and - wires reversed, but otherwise you can just plug them in. I didn't even have to change anything in firmware.
They should light up when nothing is in the beam, and the lights should go out when triggered. If not, the wiring is wrong.
If you use just the optical sensor, that's a bit trickier, but to use something like this:
[www.ebay.com]
You can almost just plug them right in and work.
Some have the sensor and - wires reversed, but otherwise you can just plug them in. I didn't even have to change anything in firmware.
They should light up when nothing is in the beam, and the lights should go out when triggered. If not, the wiring is wrong.