by geekrex @instructables
I am such a guy who loves his thing very much and specially i don't like any one coming to my work space without my prior knowledge,mostly if the persons are my sibling or young kids.I need a way to make an alarm to help me protect my space and guard it properly.
But buzzer are too low in volume to implement.Until i got this . A freaking loud siren from DNA technology.
It was so loud that i had to wear plugs before i had to turn it on.
I just loved it but also needed to decrease the volume of the siren , which i achieved by using a pwm ,which i will explain later.
I coded a simple sketch in arduino to input from a ultrasonic sensor and if their is somebody near 100 cm of my workplace it ativates the alarm and stays on still the person is present.