# Piezo power!

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#### Impathy

##### New Member
Hey everyone!

I'm revisiting an old project that I abandoned due to lack of time and knowledge. I've looked everywhere but I assume what I'm trying to do is too advanced for a starter like me. So here's my problem: I have a piezo transducer. When deformed, it generates a small voltage. Roughly around 3v. That's the simple part. I've also got a powerful light on its own separate circuit. This light requires 125v to be fully powered. My question is this, how do I make the voltage of the light depend on the input voltage of a piezo. For example, the piezo is idle, no deformation is being applied. Therefore it outputs 0v. The light should have an input of 0v. Now say the piezo is being fully deformed and is putting out 3-5v. The light should now be at a full 125v input.

Is this possible? And if so, should I try and tackle this as a novice? I've been trying to teach myself electronics over a long time and must be missing something because I can't understand all of the technical jargon when attempting this project.

##### New Member
Essentially you want to transform 3-5V to 125V. You could, but you would Get nearly 0 amperage.

#### Impathy

##### New Member
That's no good... I need the amperage!

Is there perhaps a way to not necessarily transform the voltage, but use it as an input for a controller of some sort that outputs voltage? I'm not sure if that type of thing even exists.

#### weegee

##### New Member
I dont think the OP wants to step up the piezo, but rather use it as some kind of pressure sensor, that has a linear output based on the input.

#### Impathy

##### New Member
Exactly weegee!

Does that type of thing exist? Something that has a linear output based on input? Because that would be the perfect thing for what I'm doing.

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#### Andy1845c

##### Active Member
I assume the 125v for the light is AC? What kind of current does it draw? If you just want on and off, you could use somthing like a solid state relay and appropriate circuit to drive it. If you need a variable 0-125v, its going to be harder to do. Thats a bit out of my scope of knowledge. I can only assume you want to dim the bulb. Modern dimmer switches don't alter the voltage, but rather, rapidly pulse power to the bulb. The duty cycle determins the brightness of the bulb.

#### Impathy

##### New Member
Yes, it is AC. And I don't know the draw off of the top of my head... I'm trying to see if this is even possible before I get my components out again, Lol. As for the actual light. I was hoping for variable brightness from unlit to fully bright. However, I might have to settle for a simple on-off circuit driven by the piezo. Thanks Andy. Time to research solid state relays... Anyone else have any ideas of how to drive a 125v light with my piezo?

Edit: Instead of a SSR, what about a Triac? I'm not very familiar with them but read something that says "...TRIAC a very convenient switch for AC circuits, allowing the control of very large power flows with milliampere-scale control currents." And says that they have common uses for dimmer switches or fan speed controls. Couldn't this be adapted to work with a piezo input for quick pulses of light when the disc is deformed?

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#### weegee

##### New Member
piezo > pic.ADC > pic.PWM > triac > light

that should give you a pressure sensitive lamp dimmer, but i would imagine you would need some protection circitry to protect the pic making sure the input from the piezo doesnt go to high, as if you strike the piezo you can get enourmos voltage from it.

#### Andy1845c

##### Active Member
Impathy said:
Edit: Instead of a SSR, what about a Triac? I'm not very familiar with them but read something that says "...TRIAC a very convenient switch for AC circuits, allowing the control of very large power flows with milliampere-scale control currents." And says that they have common uses for dimmer switches or fan speed controls. Couldn't this be adapted to work with a piezo input for quick pulses of light when the disc is deformed?

Well, I have never played with a piezo this way before, but I would imagine it only makes a voltage as it is being deformed, or pressed on, and not as it is held down?

What exactly are you trying to do? Do you want to be able to switch a light on and off, rapidly tap it to blink a light, make it respond to loud music? I'm a bit confused the more thought I give this. Is there somthing more appropriate to use then a piezo?

#### Impathy

##### New Member
Lol, just as I added that edit you responded weegee...

Sorry for my lack of knowledge, but could you please better explain "piezo > pic.ADC > pic.PWM > triac > light"? I'm just not familiar with the acronyms. I hope I don't sound to silly asking what pic.ADC and pic.PWM stand for. I can only guess that those are two types of programmable pics? Or I could be completely wrong.

#### Impathy

##### New Member
Andy1845c said:
What exactly are you trying to do? Do you want to be able to switch a light on and off, rapidly tap it to blink a light, make it respond to loud music? I'm a bit confused the more thought I give this. Is there somthing more appropriate to use then a piezo?

Good question!

I'm a drummer. I would simply like a cost-effective method for building a bright light that is triggered by striking the surface of a drum. Currently I only care about my bass drum (The big one that sits on the floor.) So by gluing a piezo to a larger metal disc to give it more surface area, I can make the piezo deform every time the base drum beater hits the drum skin. This technique is used by lots of drummers to make an electric set from acoustic drums. The output from the piezo can be input into a midi controller to play audio/midi patches for example. I simply want a light to be triggered instead of a midi patch. Without having to deal with a big controller box. I want to try and keep it simple. Any better suggestions?

#### weegee

##### New Member
the pic.adc is an analog to digital convertor, so the pic can process the voltage it has recieved, and the pic.pwm is the pulse width modulation output to control the triac.

basically read a value on an adc pin on a pic processor, convert it as neccessary and send it out as a pulse width modulated output to the triac. the pulse width controls how bright the light will be

#### Impathy

##### New Member
Awesome, thanks weegee!

I'll have to do some more research on those before I actually try and implement them. I've never used either of them before. Any suggestions for where to get a good start on ADC, or PWM?

#### Nigel Goodwin

##### Super Moderator
Well now you've told us actually what you're doing, have a look at this, a PIC based MIDI drum kit, it should be easy to extract the parts you want.

#### Hero999

##### Banned
PWM isn't any good for AC as the frequency would need to be lower than the mains which would cause the lamp to flicker; phase control is normally how it's done.

A potentiometer controlled dimmer is easy but voltage controll is much harder. You can use a PIC but I designed this circuit awhile ago.

#### Impathy

##### New Member
Thanks for the help so far all. I'm definitely going to have to do a lot of learning and experimenting before I conquer this project. The more and more research I do, the less and less confident I am with how much I thought I knew.

Hero999, what do you think would be the simplest and most cost effective way of setting it up?

I'm starting to consider that I can live without pressure sensitivity. So would a SSR be the answer? Thanks.

#### krazatchu

##### Member
Hey~~

As someone mentioned previously... the piezo will only output AS it's being deformed...
It can be used to sense movement... but not force....
This should be suitable for your application....

Check this link, you will find the first half of what you need (the sensor)...
http://www.discovercircuits.com/DJ-Circuits/vibrationalarm.htm

Then you jsut need something to switch the light...

#### krazatchu

##### Member
You may also want to swap the invertor for one with a schmitt trigger...
Otherwise you may see some of the aftershock...

#### Hero999

##### Banned
If it doesn't need to be pressure sensitive then it makes things much easier. All you need a comparator and a flip-flop to controll a small relay. Tap the piezo once to turn it on and again to turn it off.

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