Hi, I'm a physics student from Nigeria and I'm interested in doing a project involving piezoelectric transducers.
The project will deal with how a piezoelectric material can produce voltage from the mechanical stress of a human footstep,
so my first question would be how and where can I find (buy) a piezoelectric transducer (plate) that can withstand the weight
of a footstep and is not so sensitive to vibration that any little disturbance will produce voltage. Or how can I dampen the
voltage response produced from ordinary vibrations/sounds/disturbances?

Please suggest which of the following products on Aliexpress.com will be best suitable for this purpose (that's basically
the only place I can easily get these piezoelectric materials shipped to Nigeria)

http://www.aliexpress.com/item/High...c-Transducer-Cleaner-45mm-Dia/1740089597.html

http://www.aliexpress.com/item/Genu...ceramic-humidifier-accessories/907653251.html

http://www.aliexpress.com/item/Free...c-chip-piezoelectric-ceramics/1981491165.html

http://www.aliexpress.com/item/Ultr...ric-ceramic-ultrasonic-sensor/1758147590.html

http://www.aliexpress.com/item/5pcs...ent-Ceramic-Ring-freeshipping/1353867677.html

If none of these piezoelectric products can do the job, can you please suggest where I can get the right materials.

Secondly, I need the piezoelectric transducer to act as a sort of trigger/sensor such that the voltage is maintained for as long
as the foot is on the device, as soon as the foot is removed, the voltage should be cut-off. Can the circuit described in this
thread (using IC 555) be used for this specific purpose?

http://forum.allaboutcircuits.com/showthread.php?t=80497

Can you give me any TESTED circuit where a piezo trigger (or sensor) is made to produce constant voltage when pressed (or strained
in one direction) and voltage is cut-off when pressure is released.

Will be expecting your informative replies. Thanks.

 

Hey,
This seems to be the one piezoelectric material suitable for such a application. But i do not know if they will ship to Nigeria. But maybe you can get someone to buy and send it to you.
http://www.faceinternational.com/
Goodluck.

 

A piezeo disc will not maintain a voltage but when flexed in one direction will produce a + pulse, when reversed, produces a - pulse. Using a piezeo speaker element, 2 cm dia disc, maybe like second ref, /Genu/ , made a sandwich of 1/8 cork sheet; cork , disc, cork, 1/2 plywood top cover. On stepping on it, a 30 V neg. pulse, 40 ms fall tine 60 ms recovery; on release, 25 V + pulse produced with same rise & fall times. About 5 V P-P noise present.
To detect, I think comparators would work by biasing one disc to about 9 V to det. _ pulses, other set to det. + pulses. Arrange outputs so that pressure produces a neg. pulse to trigger a 555; release of pressure to reset 555.

 

I made a simple 12" square "footstep sensing plate" by attaching the piezo disk from a large beeper to a piece of 1/2" acrylic with some double faced tape.
The output went to a simple high impedance amp. it worked pretty well considering the simplicity.

The key is mounting the disk with a semi flexible adhesive, to control the stress on the piezo disk. I mounted the sensor underneath in the center.
Support the edges of the plastic, so it flexes from the load.