Looking for a vibration switch/sensor attachable to a metal plate

[br22]

Guys, this is probably so simple for you, I have searched the forum but my problem has not been asked before.

I want a switch/sensor that I can attach to a metal plate so that when the plate is hit, it will either make or break a circuit to stop a timer.

br22

 

[FvM]

Re: vibration sensor

my problem has not been asked before

Even the rather thumb "Similar Threads" tool suggests different. The board search has much more hits. I remember some of the previous discussions, they are not actually far from your question.

 

[Nick C.]

Re: vibration sensor

There are many ways to do this. The easiest would probably be to use an off-the-shelf shock sensor used in burglar alarms.

One roll-your-own method is to use a piezo disc as a vibration sensor. Here is a sample circuit with more detailed information at the provided link. You can find more of these types of circuits in Forrest Mims' various books.

**broken link removed**​

The piezo speaker is connected to the input of an op amp operated as a comparator. This operation is achieved by eliminating the usual feedback resistor between the output (pin 6) and the inverting input (pin 2). In operation, subtle vibrations cause the piezo element to generate a small voltage. The LED glows when the voltage exceeds that applied to pin 3 of the op amp by sensitivity control R2.

 

[br22]

Re: vibration sensor

Thanks nick

br22

 

[TracyW]

Re: vibration sensor

Wow,it is great!

 

[pranam77]

Re: vibration sensor

The cicruit here in the link is a Shutter guard which is implinented to sense vibrations using a piezo element and sound a siren.
**broken link removed**
Cheers

 

[dr pepper]

Re: vibration sensor

I dont want to sound simple, but have you thought of a mechanical switch, you can get adjustable vibration mechanical switches for security systems, the older cheaper ones were mechanical, later ones are complex items with frequency spectral recognition.

 

[Nik_2213]

Re: vibration sensor

IIRC, window-guard sensors may only be sensitive to vibration in one plane and at high frequencies lest traffic rumble set them off. A piezo transducer's response may be tailored to sensitivity required.

FWIW, I've used a vibration sensor plus a digital timer to calibrate the run-back timers on lab shakers etc. I found that the lithium-cell powered timer needed a few uF across contacts but then started and stopped within a second...