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Basic Circuit Question?

I am making a box that when opened will sound an alarm.  When it is closed, the contacts are touching, thus completing the circuit.  When the box is open they are not touching.  How can I make a circuit that will realize when theyre not touching(without using an Arduino or other programmer)???


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lemonie6 years ago

You can do this without a microprocessor, but why not make a switch that works the other way?

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To further Lemonies sound answer, most microswitches (those little switches you'll see if you crack open a mouse that engage with very low travel) are configured as SPDT or single pole, double throw switches, meaning that they can be used either as a normally closed or normally open switch, allowing you to choose the mode per application.
Picture of two microswitches found inside an old computer mouse:
old-mouse-microswitches.jpg
Thanks Jackalopes. Exactly what I meant.
220px-Microswitch.jpg
crocboy (author) 6 years ago
Thanks lemonie! I just kind of had a brain fart and never really thought about that.