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Ever wondered how it is that elevator doors these days have the kindly
habit of not crushing people... well its all about laser tripwires.

We build a laser tripwire by using an LDR which is connected to an Arduino analog pin through a voltage divider. Thus the reading on the analog pin varies with the light. Next we point a laser at the LDR and write a bit of code that says if the value goes down then trip the Alarm!

Component List:

•Arduino Uno

•5mm LED

•Piezo Buzzer

•Laser Module

•Light Dependent Resistor

<p>I have been looking at all the laser tripwires and this is great for my first project, Could you please tell me how to repeat the buzzer for another 5 times please.</p>
<p>its ok i have figured it out!</p>
<p>Lost my laser module but found the setting sun worked great for testing</p>
<p>Thanks for this, great tutorial</p>
<p>Very cool! I've always wondered how elevator doors and stuff like that worked. I always just figured it was magic.</p>

About This Instructable

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Bio: I am robotics engineer and a teacher whose passion in life is breaking down the maths and academic jargon of programming and robotics into something ... More »
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