Hello all,

This is my first post so just want to say hi to everyone.

Now to begin with I'd like to say I probably have an "average" or "limited" electronics knowledge. I'm not a "newbie" but I'm not advanced quite yet.

I was going to add LED's activated by, well at first I did LEDs activated in my Drum snare via a MIC and some other parts. But that had issues with interfering sounds etc. So I was thinking about the Rockband and Guitar hero drum sets. I knew they used Piezo sensors to register the hit. You know the circular gold and silver thin wafers?

Well I decided try that instead. I figure there must be some way to convert the use from that to lighting up an LED. Just as an FYI I will be using 4 Red 5mm LEDs with a forward V+ of Max 2.5, 20 mA. Now actually For this project I am building a drum pedal for Rockband with a real drum pedal, a practice pad, and another piezo sensor (just transfered from it's original housing to the practice pad, so that part's complete.) So what I'm saying it won't be for real drums so it won't have to dissipate quite as rapidly.

I have messed around with it most of the afternoon and got nowhere. So now I need some help. Any is appreciated!!

Thanks so much!

 

Anyone? I really need some help on this..

 

U said u got one working, then please post the schematic so I'll see what I can do.


Rifaa

 

No i mean I got it working using a MIC, but that had issues with other sounds setting it off etc. So I was going to try using piezo 'sensors'. I don't really have a schematic made as I was just trying different condemnations with my soldering iron and the parts. Haha..

I honestly am not sure where to start..

 

Take a look at the Door Knock Beeper at http://www.discovercircuits.com/DJ-Circuits/door-knock.htm -- it may give you some ideas.

--Rich

 

I think what you need is a tuned circuit which responds to that frequency you want.
You have to use a condenser mic probably a ADC too, might get complicated enough if the circuit is not built and tested by some one who knows what you exactly wants.

Please explain in every detail you can.

Rifaa

 

No no guys, I want to do with with a piezo sensor forget the MIC that's not what this is about.

 

Hello,

Those piezo parts give sharp high voltage low current pulses.
You can try to trigger a monoflop with the pulse to have the leds light up for a while.

Greetings,
Bertus

 

I don't really like the idea of using a monoflop as I was thinking more of something that lit of when the beater struck the pad, then immediately went off.

 

hello,

The pulses will be to short (the order of several microseconds).
You will have to strech then to something like 50 - 100 mSec.

Greetings,
Bertus

 

Piezoelectric devices can put out significant voltages with tiny amounts of current. If I was trying to do this, the first thing I would do would be to connect a scope to the piezoelectric device and see what it was putting out. Then it's almost certain that an op amp and a pulse stretcher would be necessary. If you don't have access to a scope, then a general approach would be to put an op amp with reasonable gain, a comparator to normalize the voltages, then a digital pulse stretcher. Lots of example circuits around the web for those tasks.

 

Good point,

Well now onto the circuits. As I said I'm not the *best* at these sort of project's where I don't know exactly what I'm doing hahaha..

I didn't see your post,

I do not have access to a scope, and did you mean 'capacitor'? or did you mean what you said, 'comparator'. Also is there a way I can make the Piezo element more/less sensitive using a variable capacitor?

 

Here is my schematic, How is it.. will this work?

 

Hello,

I think not.
There are a couple of things that need change.
The visual senstivity led will put a to high load on the piezo.
(there will be hardly any pulse on the gate of the fet).
The leds on the output should have their own series resistor.
(the way it is now connected the leds will die one afther another due to different currents in the leds).
The Fet is now connected to the powersupply, a N-gate fet is normaly connected with the source to ground and the load is connected between the drain and powersupply.
You can protect the fet against the high voltage peak of the piezo with a 10 Volts zener at the gate to source.

Greetings,
Bertus

 

Uhm It will take a few minutes to decipher what you said to fix my schematic haha. But about the LED's. They are all (will b) exactly the same, I just listed 3.2v-3.8 as that's the min through max of the LED's.

Also is there any way to have a visual indicator of how sensitive the piezo the piezo is. I wanted to have something like this as different people have different strength and one may not hit the beater very hard so nothing will happen, or the other way around. I wanted to have some way to adjust that.

Also I can't find the 2n7000 stocked at Mouser anymore. I really only like to shop there as I order new parts almost every day so I have like 12 orders to try and keep track of. So do you have any suggestions about that?

 

Hello,

Here is my idea for the piezo to led.

The diodes ai the input of the opamp protect the opamp against high voltage pulse when beaten very hard.

There is no pulse stretcher yet.

Greetings,
Bertus