In the microcontroller era today, Arduino is ... 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 ...

[Gord Payne] has one with an elegant sensor ... of light reaching the LDR from the LED decreases as the pipe is bent, and with a simple divider circuit a voltage can be read by an Arduino.

The on-board 1-MΩ pull-up resistor calls for a very high-resistance LDR, but the most common ... The code is an Arduino project for the Digispark Attiny85 to turn on a light source when the PIR sensor ...