Piezo trigger circuit

[Neurotic]

The wires on the right are connected to a regular PC keyboard and if shorted they activate the letter "K" on the keyboard. The circle on the left is a piezo transducer (also known as pickup for guitars etc...) and I suppose you know what it does

The question is, how do I put this things together so when the piezo is active (in case of hitting, vibrations...) it closes the circuit and the key "K" is activated. I suppose I need some kind of amplifier cause the piezo alone generates very weak signals.

I am not skilled in electronics, besides basic soldering and understanding, so I guess I'm gonna need you to draw me a full scheme so I can build this.


Help would be much appreciated.

Neurotic

 

[Fish4Fun]

Hey Neurotic! Welcome to EP!

The biggest problem is that a PC key board is a "Matrix" that is constantly "scanned by Row & Column".....any given key's state is decoded based on it's "address" within the matrix.....in short, you aren't going to get this to work THIS way....If you truly want to achieve a "sound" when the "K" is pressed the best approach would be to write a "key logging program" that outputs a "beep" on the system speaker when the "K" is pressed.....if need be you could replace the system speaker with your piezo....or you could use a comm port it there is one available...if not, then you could use a USB to COM interface and simply connect the piezo to +3.3V or +5V and the IO_Out line...then your program could simply send a series of data packets to the Comm port when the "K" was pressed.....

Good Luck!

Fish

 

[Gryd3]

You could get something like this running pretty quickly through software with a very simple program that allows you to customize a 'hotkey'
Take a look at AutoHotkey, as this program allows you to make scripts or executables that run based on keyboard/mouse/joystick input. (Not suitable for 'key-logging' as it will only look for pre-determined key combinations and will not record keystrokes. This is a good thing!)

You could also put a little more brain into it and program a small microcontroller to sniff the USB transmissions from the keyboard for the 'K' key. This would operate on any OS, as the microcontroller would take care of it for you.

 

[KrisBlueNZ]

AFAIK he wants to simulate pressing the letter K when the piezo detects vibration. This could be done by hacking a reed relay contact across the pushbutton contacts for the K key on the keyboard. But the criteria for activating the relay are not clearly defined.

 

[Fish4Fun]

oh.....so my dyslexia has now crept into entire paragraphs....it is no longer just a dog/god problem :-(

Fish

 

[Neurotic]

I want the keyboard key "K" to be triggered as soon as the piezo detects vibration. A collaboration between the piezo transducer and a dismantled PC keyboard It is for a non-velocity drum machine using PC, regular pc keyboard and software. I think I'll be going with optocoupler, similar like below: