Vibration sensor for photography.

This ultra sensitive vibration sensor works with the universal detector for DSLR.
It is able to detect a simple shock of a fingernail on table.

This sensor is very simple to perform, it has only 4 resistors and a capacitor.
No active electronic component is required only passive components.
The principle is very simple, using a piezoelectric wafer with a rod and a weight.
Each vibration picked up by the weight and the rod is transmitted to the piezoelectric wafer
that generates a very small voltage.
To amplify the very small voltage, I simply used two resistors from very high value in series
with the piezoelectric wafer. This avoids having an amplification by an active electronic component.
The electronic circuit has a very high impedance.
The Arduino who is integrated into the universal detector is capable of handling
sensors with very high impedance.

The voltage is low, it is between 10 mV (millivolts) and 1 Volt.
This voltage is alternative (positive and negative).
The entry "AUX" of the universal detector for DSLR reflex does not support negative voltage.
We must therefore create a bridge voltage divider with two resistors of 10 KOhms and a capacitor of 10 uF.
The bridge voltage divider provides a voltage between 1.5 volts and 3.5 volts maximum.
The entry "AUX" is made to operate with voltages between 0 and 5 volts.
So there is no problem.

To realize this vibration sensor, you need a piezo disc as the Photo01 and photo02.
The one I used, is an old piezoelectric disk that I recovered from a watch.
If you do not have an older watch, you can buy this type of piezo wafer in electronics store or
on the internet for 2 Dollards.
For example, on the website http://www.E44.com, under references HBE or HBE2.

On the photo03, the block diagram of the vibration sensor.
A piezo wafer connected to two resistance of 6.8 MOhms (mega Ohms) in series.
The bridge voltage divider consisting of two resistors 10 KOhms (Kilo Ohms) and a
capacitor of 10 uF / 16 V (you can put a capacitor of 10 volts or 25 volts).
The stereo jack that connects the assembly to the universal sensor for DSLR.

On the photo04, the drawing board layout on a printed circuit pre-drilled (PCB diagram).
On Photo05 and photo06, the complete assembly achieved.
The rod is a rigid wire 2 inches (5 cms).
The weight is a screw of ten grams.
As you increase weight, the sensor is more sensitive.
As you increase the length of the stem, the sensor is more sensitive.

On the photo07 and the Photo08, the assembly placed in a small box.
To use this vibration sensor for photography, you just putting the box on the surface
hat will receive the vibrations and adjust the UNIVERSAL SENSOR FOR DSLR on "AUX",
select "MANUAL VALUE", set "550" such as a value for exemple and select "ON UPPER".







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Copyright 2011-2012 ThierryD - http://rienquepourlesyeux.free.fr
Last update 05/01/2012
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