This is an optical end stop for a CNC project I am working on. It uses an OPB615 and has no moving parts. The OPB615 is active low, so the output pin is high until there is an obstical in between the emitter and the sensor and it goes low when an obstical blocks the beam. This version of the project has indicator LED for both power and signal. This project can be used for all sorts of things other than CNC end stops. I will also be using it to replace contact switches that currently tell my home made home automation system if the garage doors are open or closed. There is a 390 ohm resitor doing current regulation on for the emitter diode. That value provides ~10 miliamps at 5 volts. Although you may wish to use a higher current for the emmiter diode as it is rated up 50ma. If you use this with other voltages please be sure to atjust the resitor. Also please note that R1 is a R1210 and this is to accomidate a .5 watt resistor if you are using a higher supply voltage. I have four of these running at 12 volts for me CNC limit switches and at 12 volts with 40ma for the LED it requires an .5 watt resistor. You can use a R1206 for smaller wattage resitor if necessary. Important note, this detector as mentioned is optical. That means it can be affected by the sun or other bright IR sources. The OPB615 can operate up to 18 volts so it can be used in all sorts of applications.