Breath triggered LED light with piezo sensor

[arielleandreotti]

Hi everyone,
I am a graduating student of the Design Academy Eindhoven and I guess I have a very simple question : I made this circuit with an LED that turns on when you blow on the piezo, but I have two questions about it :

- how to integrate the circuit into an actual lamp? replacing the one single LED by LEDs trips and connect the whole circuit to main supply (not the computer), around 12V
- This piezo is not very sensitive because of its plastic shell around, does anyone know where precisely I can find an uncovered piezo sensor, with a bigger reacting metallic surface?

Thank you a lot!

[polymorph]

Using a piezo without a case won't necessarily make it more sensitive.

What you need is a preamplifier. Even an LM386 amplifier should work for this.

[arielleandreotti]

The thing with the case is that it prevents most of the breath to even reach the sensitive surface

I found a lot of these flat shaped piezo transducers, most of the time it is used in electrical instruments, do you think that would be suitable for my purpose?

thanks!:)

[polymorph]

You keep saying "breath sensor", but it really is a "noise of blowing sensor". It isn't detecting the moisture in your breath. Just making sure you know that.

As I said, simply removing a piezo from a case may actually make it less sensitive at picking up sound. There is a reason that microphones and speakers come in cases, to separate the front from the back to avoid having the sound partially cancel is the primary reason.

Seriously, just add an amplifier. A simple Op Amp circuit, or an LM386 audio amplifier.

[arielleandreotti]

I say breath sensor because I am actually using the pressure it applies on the piezo, so it's not reacting on sound but on pressure, that is why it would work better if the accessible surface was wider
I in fact also working when you press something on it

[polymorph]

Are you sealing your lips over the hole in the piezo case and blowing? If not, then it is responding to the sound of your breath blowing by the hole.

Yes, I'm sure it also works when you press on it. It still isn't the same thing. Put your oscilloscope on it, or connect it to an amplifier and listen to it.

[Boardburner2]

I would think its responding to sound also.

Afaik piezos only respond when moving.
Constant pressure does not gererate a charge

[vanakaru]

http://www.ebay.co.uk/itm/10-x-27mm-Piezo-Elements-Sounder-Sensor-Trigger-Drum-Disc/121419571205?



and try preamp, but be aware that you get reaction from loud sound before you blowing. But there is a MIDI-wind-instuments made with piezo pickup

https://www.youtube.com/watch?v=mGHIJaN5q6c

For practical application in light fixture search for non mechanical switches.

http://hack.lenotta.com/arduino-raspberry-pi-switching-light-with-nrf24l01/