If you’re looking for something to do this weekend, consider this PIR (passive infrared) Sensor Alarm project. Not only will the motion-sensing alarm ...

Our schematic consists on 3 elements which are: Photoresistor (LDR), Piezo Buzzer, 1 – 10 kΩ. The LDR can be connected any way you want because doesn’t have polarity. For resistance you can use from 1 ...