As found in the schematic of the ... comfortably see ambient light through the Fresnel lens. To be frank, using a microcontroller is probably overkill for most motion detector safety light circuits ...

With just a Wemos D1 Mini, a standard PIR sensor, and some open source code, you can create a practical self-contained motion sensor module that ... and provided a wiring diagram so there ...

Because of the affordability and seeming ubiquity of the Arduino platform, they have been hard at work this last month trying to get their Geiger counter sensor board for an Arduino out the door.