Vibration sensor

[dsesmg]

Hi, I am trying to study on using a vibration sensor like this one.
http://www.flickr.com/photos/34955071@N02/3892827302/#sizes/l/
http://www.flickr.com/photos/34955071@N02/3892827306/#sizes/l/
http://www.flickr.com/photos/34955071@N02/3892827314/#sizes/o/
http://www.flickr.com/photos/34955071@N02/3892827320/#sizes/o/
http://www.flickr.com/photos/34955071@N02/3892827322/#sizes/o/
Sorry, I couldn't link the PDF. So, I just posted it seperately.
My goal is to use this sensor to break a circuit of a motor when it gets to receive a certain vibration threshold so that the whole system of a machine can be safely stopped, therefore, preventing any phisical damage of a machine when it goes wrong, by sensing the vibration of a machine.
http://www.flickr.com/photos/34955071@N02/3694441534/#sizes/o/

[Soeren]

Hi,

Hi, I am trying to study on using a vibration sensor like this one.
[Snip]
Sorry, I couldn't link the PDF. So, I just posted it seperately.

Here's the page for the sensor
http://www.meas-spec.com/product/t_product.aspx?id=2484
And this might get you the datasheet (otherwise get it from the page linked above).
http://www.meas-spec.com/register.aspx?id=2030#
Else, there's these:
http://www.makingthings.com/resources/datasheets/acc_piez_001.pdf
http://www.ehag.ch/PDF-Files/MSI/ldt0.pdf

My goal is to use this sensor to break a circuit of a motor when it gets to receive a certain vibration threshold so that the whole system of a machine can be safely stopped, therefore, preventing any phisical damage of a machine when it goes wrong, by sensing the vibration of a machine.

The LDTx is a piezo-sensor and could be likened with eg. a crystal microphone (a thing of the past, but you may have come upon them).
They cannot switch anything, just give an output which could then control a switch circuit.

Here's an example of a circuit that would work, giving a short timed output which could control a relay (which it was designed for).
It was designed for a regular piezo disk glued to a steel plate, to detect GOLF ball hits (for "target" practice), but the working principle is the same.

To use it for vibration sensing, it should be changed to react, only to a certain amount of vibration and the mechanical setup should be tailored to the resonance frequency of the vibrations, which should be known beforehand.

For a vibration sensor, a cheap piezo disc could be used as a Guinea Pig to save the LDT0.

[dsesmg]

Hi, thank you very much for such a wonderful guidance.
I will get the parts shown in the drawing and I will do it.
I've been thinking about how to use this vibration sensor to break AC motor power supply.
This is what I came up with.
http://www.flickr.com/photos/34955071@N02/3895893820/#sizes/o/
The relay shown in the drawing is this.
http://pdf1.alldatasheet.com/datasheet-pdf/view/95519/ETC/JZX-18FF/ADC4Z3QD.html
So basically, I need to break the AC power connection when the vibration sensor triggers the N-Channel MOSFET, as a result, converting the normal close to normal open.
Is this method workable?
Will this breaking method stop the motor only for a moment when the vibration sensor gets the maximum threshold?

[Soeren]

Hi,

I've been thinking about how to use this vibration sensor to break AC motor power supply.
This is what I came up with.
http://www.flickr.com/photos/34955071@N02/3895893820/#sizes/o/

That won't do it.
First off, The sensor should be isolated from DC.
The output from the sensor, on a steady vibration, will be close to a sine wave. so if there's no vibration, there's no output. Since it's an AC wave, it would have to be rectified and integrated as the very least, to avoid just amplifying the pulses/waveform.

The relay shown in the drawing is this.
http://pdf1.alldatasheet.com/datasheet-pdf/view/95519/ETC/JZX-18FF/ADC4Z3QD.html
So basically, I need to break the AC power connection when the vibration sensor triggers the N-Channel MOSFET, as a result, converting the normal close to normal open.
Is this method workable?
Will this breaking method stop the motor only for a moment when the vibration sensor gets the maximum threshold?

As mentioned above, it won't quite cut it and it would be momentary.

This circuit http://That.Homepage.dk/PDF/Vibration_Kill_Switch.pdf could be used - R1, VR1 and C3 will need to be adapted to the sensor and the amount of vibration you'll allow before it shuts down.
The terminals PB_START is for a pushbutton to reset the circuit (starting the motor). IC1A and IC1B makes up a flip-flop that makes sure the motor keeps off when triggered by vibration. The relay you selected will work with this circuit.
The rest should be self explanatory, but do ask if something puzzles you.

[dsesmg]

Oh... thank you very much for helping me out. I will try that schematics for this vibration sensor.
I was wondering on determining the amount of vibration I allow.
The application is for the conveyor project I am proceeding at the moment.
This conveyor structure is comprised of 4 rollers(5m per each). Those rollers creates some moderate vibration when the conveyor is running.
The idea of using the vibration sensor is to protect the conveyor when something breaks or loosened in the internal assembly of the conveyor causing severe damage during the conveyor running.
Because, this conveyor is only for a hobby. Unlike the commercial sorting machines, this thing is very very flimsy.
It seems that the table 1(LDT0 as vibration sensor) shown in the specification of LDT0, shows the example thresholds(please correct me if I am wrong) and I want to try out those all 4 criteria so that I can get the idea on how much vibration does it require to trigger the stoppage of the motor.
But, please please advise me if such idea is not the right way to determe the certain allowable vibration amount.
If it is ok, then, could you tell me what VR1, ZPD12 is, and how R1, VR1, C3 should be adopted for the 4 criteria shown in the table 1 of the LDT0 specification?

[Soeren]

It seems that the table 1(LDT0 as vibration sensor) shown in the specification of LDT0, shows the example thresholds(please correct me if I am wrong) and I want to try out those all 4 criteria so that I can get the idea on how much vibration does it require to trigger the stoppage of the motor.
But, please please advise me if such idea is not the right way to determe the certain allowable vibration amount.

The examples are for a sensor loaded with different amounts of weight, which of course changes the sensors frequency of resonance.
The best way for you to find the point of stopping, will probably be to first loosen a screw or two - just enough to increase the vibrations above normal running and then adjust the circuit to trigger a stop. Then re-tighten the screws and check that it's running normally without interruptions (might take a couple of tries to get it right).

[...] could you tell me what VR1, ZPD12 is, and how R1, VR1, C3 should be adopted for the 4 criteria shown in the table 1 of the LDT0 specification?

It will involve a bit of trial and error, but for initial values, try 100k for R1 and VR1 and 100nF for C3.
ZPD12 is a 12V zener diode (use any 12V zener of at least 1/3W).

When you know the approximate position of VR1, you can refine the values.

[dsesmg]

Thank you.
I will try to test and face some tries and errors.