Tilt/Vibration Sensor

[Demon]

A variant on the wire/spring idea; use the coiled spring from an old thermostat. Add a drop of lead on the tip to act as contact.

You might be able to have two axis by placing two springs perpendicular.

This of course is totally theoretical.

Robert

[Jerson]

A quick image search on google for 'mercury tilt switch' showed a lot of those bulbs and 'non-mercury tilt switches' are now the norm.

I found some commercial vibration sensors using the spring sensor here
http://www.aliexpress.com/store/grou...210931515.html

[Ioannis]

Mercury is not allowed anymore. So other solutions like the spring type or ball like the one I am using is prefered.

I have ordered a packet of 200 pcs spring type sensor and will see if it works as expected. Since this is a production design, I cannot experiment with diy coils or springs. Thanks all for the ideas, but a ready made solution is prefered.

I have a feeling that either sensor, the one I am using now (see the pdf on the #1 post), or the spring type, it will need some kind of filtering or integration. Maybe the idea of a resistor-capacitor will help as AvionincsMaster1 posted.

Ioannis

[AvionicsMaster1]

Woohoo! I might have gotten something right!

Have you thought about using something like this:ADXL345 3-axis Digital Tilt Sensor Acceleration Module. I know it's for Arduino but I'm sure a similar solution could be forund for PBP and they're fairly cheap but I was too lazy to look for one. They probably aren't as cheap as your vibration sensor though.

I did find some two axis tilt sensors but if you're doing an alarm you might want the three axis and I think an accel would work well. The math for it looks daunting http://www.freescale.com/files/senso...ote/AN3461.pdf. You could also use IOC with the accels which I think would be easier by just looking for a raw voltage change. I realize this system probably won't be used in the National Art Gallery but it could be made to be fairly sensitive using accelerometers.

Good luck.

[Ioannis]

I forgot to mention that the circuit will be battery powered with the need to work for a long time. Say for months. MCU will be in sleep and when shaked, an interrupt wakes it, does its magic and goes back to sleep as a good kid.

Thanks for the moduleidea, it is a good but is very expensive for this project. The target price per device is about 7-10 euros max.

So for now, I'll stick with the mechanical sensors.

Ioannis