With the thousands of Arduino ... the main code sporting a simple "if-else" logic. You can readily use the project developer's code as is or change the pin configuration and the LDR's threshold ...

Here is an ultra simple Arduino Night ... Here an LDR (Light Dependent Resistor) is used to measure the light level. The alarm system is triggered when a “Logic High (H)” level signal is detected at ...

The principle of this setup is somewhat simple ... proximity sensor drives an infrared emitter to illuminate an object, then looks for the reflectance from the object to detect its close proximity.