Tilt/Vibration Sensor

[Ioannis]

Cant you use an interupt that will start a timer when the circuit opens.. and then you use an interups to stop the timer when the circuit closes and reload timer.

Then you set up the timer to overflow at a suitable time. If the box is tilted the timer will overflow and give you a timer interupt. If the box is just shaked the time between sensor toggle is so small so you will not get an overflow.

maybe ;-)

Yes, it is a good idea to try. But the main issue is that the sensor gives a series of pulses when triggered. Is not like the mercury tilt switch. Either shaked or tilted.

You could put a capacitor across the sensor to "average" the oscillations. Better yet, a RC network tuned to give you the desired time you want.

I'm curious though, there is nothing in the datasheet says this will work as a "tilt" sensor. Only says it's a "vibration" sensor yet doesn't give you any specs on minimum movement required to trip the sensor. If someone moved the sensor very slowly would the sensor sense that? If not, it won't work as a tilt sensor as those trip when something is tilted no matter how slowly it's moved.

Since we have a microcontroler, why make an integrator with RC net? As for the kind of sensor, yes it is more a vibration that tilt sensor, though very sensitive and can be used I guess as such.

The last time I did something like this I used a mercury bulb switch. Yes, those were still available some years back; not sure about now. A slight tilt would cause the mercury blob to move thus breaking the circuit. For a vibration sensor, a cheap chinese toy was inspiration. Just needed a straight wire soldered perpendicular to a pcb surrounded by a spring (also soldered to pcb) with a blob of solder on its end to make its end heavy. Movement causes the blob to oscillate leading to multiple closures of the contact between spring and wire.

If this kind of sensor is commercially available, please give a link. This is going to be used in a relative low production.

Thanks all for the contribution.

Ioannis

[aratti]

RS components has a lot of tilt switches, see this link: http://uk.rs-online.com/web/c/?searc...es&sra=oss&r=t

Cheers

Al.

[AvionicsMaster1]

For me simple is better. If I can put a capacitor or resistor/capacitor on something rather than write many lines of code that's better than taking the time to make the code work.

Your location says Greece so any link in the U.S. might not be viable but mercury tilt switches are fairly common here. If you have an old thermostat, the ones with the slide for setting temperature not digital, they have a mercury switch in them.

[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.