Uploaded October 2017 | Updated September 2026, 4 hours ago

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You can use Arduino ir proximity sensor for 1$ and make the rest of the alarm yourself. This is just a demonstration what can u make if you have a junkbox of electronic components lying around such as 1w LED, piezo buzzer,n-channel mosfet,3-pin connector, 5.5V regulated DC supply or 3.7 Li-on battery.