DIY Laser Trip Wire Alarm – The Learning Circuit

Now that we know how laser diodes work, it’s time to use one in a project! Karen uses a laser diode and an LDR sensor to create a “trip wire”. When the “wire” is “tripped”, meaning the laser beam is interrupted, lights will flash and an alarm will sound! To create the alarm siren, Karen couples together two 555 timer circuits. The entire project is triggered using a third 555 timer circuit used in bi-stable mode. And a relay circuit is used to control the motor and LED of the flashing alarm light: http://bit.ly/3ni865F

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