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Step 5Select a spring for the vibration sensor.
I had seen a spring-around-a-wire kind of vibration sensor in a car alarm once so I thought I'd show one off. I took apart the car alarm I had and realized two things: they were using a piezoelectric crystal to detect vibration, and it was broken which explained why the car alarm didn't work anymore.
I played with that for a bit. Basically it was a stiff piece of metal with a weight on the end. If the car was bumped or knocked, it would vibrate and the piezoelectric crystal would convert that vibration to a voltage. I played with it a little and found it would resonate around 80Hz or so which is roughly the same pitch as knocking on the side of a car. Neat.
Anyway, I was looking for a spring that would offer little resistance to being bent. To demonstrate the force, I used an business card with a couple springs I had in my collection. One was too stiff and the index card would bend, but the other was very fine and would easily yield to the force of the business card.
I played with that for a bit. Basically it was a stiff piece of metal with a weight on the end. If the car was bumped or knocked, it would vibrate and the piezoelectric crystal would convert that vibration to a voltage. I played with it a little and found it would resonate around 80Hz or so which is roughly the same pitch as knocking on the side of a car. Neat.
Anyway, I was looking for a spring that would offer little resistance to being bent. To demonstrate the force, I used an business card with a couple springs I had in my collection. One was too stiff and the index card would bend, but the other was very fine and would easily yield to the force of the business card.
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