In this experiment we are going to work with a sensor which is ... Photoresistor (LDR), Piezo Buzzer, 1 – 10 kΩ. The LDR can be connected any way you want because doesn’t have polarity. For resistance ...

Powered by an Arduino Uno, this laser tripwire alarm ... 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 ...

[Gord Payne] has one with an elegant sensor ... 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.