HI! Welcome to electrical projects channel In this video I’ll show you how to make simple “Tripwire” security alarm system There are two possible ways to make this type of alarm system Way number 1 using a relay and way number 2 using a transistor In this video I’ll use a relay Video using a transistor instead of relay you can find here: First you need to find a relay, for this project I use 12 volts relay you can use relay with different voltage. The only important thing about relay – it must have at least one set of normally closed contacts. For sound indication I use active buzzer if you don’t have a buzzer, you can make your own sound alarm device using a loudspeaker video you can find here: (link)
But better use a buzzer it is more reliable. Firs let’s check the buzzer it works and then check relay It works ok Then connect normally closed contacts of the relay to the buzzer sequentially Like this And you can check it Second step: connecting the coil of the relay to power source When you connect the coil to power source it should stop making noise, if so your device is working properly Now you can pull very thin wire and connect to this device and guard any territory Thin copper wire is very difficult to notice especially at night So if someone tears the wire you will know it. The advantage of this device is simplicity Disadvantage is that it always consumes some energy when it works, so better use power supply instead of battery If you need more energy efficient security device or you don’t have a relay than watch my second video, where I use transistor instead of relay Thanks for watching!