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Thread: Using a Piezo element to control Lasers

  1. #1
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    Lightbulb Using a Piezo element to control Lasers

    What I'm thinking is using a Piezo element, mounted to a drum head, in which when the drum is struck it'll cause the element to trigger. (a common use for Piezos in creating "drum triggers")

    http://www.allelectronics.com/make-a...EMENT/-/1.html

    Then run the signal from the Piezo element into a simple driver circuit that can create more voltage. (which I haven't figured out that circuit yet...help?)

    After the Piezo driver circuit......then what?.....maybe the modulation input of a Laser Driver? Like drlava's Fexmods?:

    http://hacylon.case.edu/ebay/laser_diode/FlexMod01.php

    These will be most likely simple TTL Lasers....how would I wire/setup the Flexmod to be TTL? (The manual doesn't say)

    Could I run the Piezo element's signal straight into the modulation input of the Laser Driver?

    The goal is to have one Laser per drum. When a drum is struck, it'll trigger it's respected Laser. (maybe around 5 drums = 5 lasers or so)

    The effect will probably be simple, maybe a single laser through a Single Fan Diffraction Grating per drum, maybe a motor with a mirror attached spinning for "The Tube" effect per drum, something simple not requiring software.

    Any help with any of the above is ALWAYS very appreciated.

  2. #2
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    Here: http://www.nerdkits.com/videos/sound_meter/

    That should generate a high enough voltage i belive.
    Im thinking about doing this with an arduino board so i can do other stuff like turn diffraction gratings and stuff.

  3. #3
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    DJDoublebass - The piezo you linked is meant to output sound. I'm not sure if it would work well(or even work) for the said application. IMO, you're better off using an optical sensor of some sort. If you play drums, you would know that any object attached on the drumskin would alter the sound or "feel".

    If you're really bent on using a piezo element, they can be found in dollar store lighters(The ones used to light candes). Be warned though; they can generate insane voltages(several hundered) with the slightest compression. I've found that some can generate voltages as high as 40V when tapped gently with a finger...

  4. #4
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    the piezo he linked to has reviews stating it worked for this purpose. It's a pretty cool idea, you will need an amp for the piezo before you connect it to a driver, but with a simple circuit it should work well. Combined with lasers, this could make a decent, sharp effect for drum solos. I'd definitely want to see it

  5. #5
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    use a high input impedance fet opamp in order to get reliable results, or a FET preamp followed by a classic 741 opamp

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    All you want to do is pick up the "hit" on the drum...

    Electret microphones are cheap and you can use a cheap
    microphone Preamp with amplitude control (a Pot) to amplify
    the signal...
    Then feed that into a schmitt trigger IC to grab any pulse over
    the level you set..
    to drown out most background noise... mount it solidly onto the
    drum..

    just my


    Jerry
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  7. #7
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    Arrow

    Quote Originally Posted by Snilton View Post
    Here: http://www.nerdkits.com/videos/sound_meter/

    That should generate a high enough voltage i belive.
    Im thinking about doing this with an arduino board so i can do other stuff like turn diffraction gratings and stuff.
    That's pretty close, but it's looking like it requires a computer to program the circuit board. I'm looking for something that's ready to go after assembly. Thanks for your input

    Quote Originally Posted by shrad View Post
    use a high input impedance fet opamp in order to get reliable results, or a FET preamp followed by a classic 741 opamp
    Interesting...it looks like that may work, but I'm not entirely familiar with op amps enough to know how to create a circuit with them from scratch.

    Know of a schematic or assembly off hand that you could point me to?

    Maybe something that can take a tiny signal, (from a Piezo) and generate 0-5 Volts, up to 9.4 Kilo ohms? (got the specs from the manual of Drlava's flexmods):

    http://hacylon.case.edu/ebay/laser_diode/FlexMod01.php

    Thanks for your input

    Quote Originally Posted by lasersbee View Post
    All you want to do is pick up the "hit" on the drum...

    Electret microphones are cheap and you can use a cheap
    microphone Preamp with amplitude control (a Pot) to amplify
    the signal...
    Then feed that into a schmitt trigger IC to grab any pulse over
    the level you set..
    to drown out most background noise... mount it solidly onto the
    drum..

    just my


    Jerry
    That's definitely a thought. I understand the electret mics, then the preamp, (a potentiometer) but I'm not very knowledgable on schmitt trigger IC's. One thing though, is that Piezos are more accurate, and I wouldn't have to worry about tuning out background noise. (there will be a TON of stage noise)

    I do however have a set of drum mics now, and a respectable sound board with direct outs per channel. "impedance balanced: <75 ohm, 0dBu, +21dBu max....." so I don't think that the direct outs will be enough juice.

    I'd have to change whatever sensor that I use every time I change heads on my drums...3 tom heads about once every few weeks, and the snare head more frequently. (kick drum the least frequent) Piezos are very cheap. It would only cost another $0.75 per head to change the Piezos.

    Would something like a relay work? Something like this?:

    http://www.allelectronics.com/make-a...RELAY/-/1.html

    Or would a Piezo create just not enough voltage?

    Thanks for everybody's efforts. I very much appreciate it.

  8. #8
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    this circuit would do the trick:

    http://www.sonelec-musique.com/image...n_meca_001.gif

    you might drop the Q1 stage and directly take the output of the second opamp to drive your trigger input... there are sensitivity and level pots

  9. #9
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    something like this velleman sound-to-light kit is already designed for you and runs off a 9v battery that has an electret microphone in it.
    you could perhaps run the power to the LED's to the modulation of the laser driver..

    The only potential problem is that you might have to put the microphone in a tube of some sort so that it only 'listens' to the diaphragm of the one drum

    http://www.vellemanusa.com/us/enu/pr...iew/?id=350678

    you can probably buy the kits more locally through radioshack or even ebay

    the bass drum would be easier to do, all you'd need is a little microswitch on the foot pedal

    Interesting project though!

  10. #10
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    the schematic I linked is relatively easy to wire on a piece of proto board and has sensitivity and level settings, so it would be applicable to any instrument, even trumpets or harmonicas

  11. #11
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    Lightbulb

    Quote Originally Posted by T0mmm View Post
    something like this velleman sound-to-light kit is already designed for you and runs off a 9v battery that has an electret microphone in it.
    you could perhaps run the power to the LED's to the modulation of the laser driver..

    The only potential problem is that you might have to put the microphone in a tube of some sort so that it only 'listens' to the diaphragm of the one drum

    http://www.vellemanusa.com/us/enu/pr...iew/?id=350678

    you can probably buy the kits more locally through radioshack or even ebay

    the bass drum would be easier to do, all you'd need is a little microswitch on the foot pedal

    Interesting project though!
    Hmmm...I wonder if the Microphone on that kit could be swapped for a piezo? Since the mic has 3 connections, one probably being power, it might not work.

    Thanks for everyones help on this, I'm really looking forward to figuring this out.

    I started to search for kits after realizing that they existed and found this color organ circuit:

    http://www.kitsusa.net/phpstore/html...g-kit-551.html

    This mic used is a "crystal microphone"....or really a Piezo....so I know that I could just swap it for a Piezo. The LEDs used could be the signal to the laser driver. I'd have to see how the circuit reacts and which LEDs light up when etc etc.

    I found this preamp too:

    http://www.kitsusa.net/phpstore/html...LIFIER-28.html

    I wish that they had more specs on it, so then I wouldn't have to assume that it would put out enough juice to trigger the laser driver's modulation input.

    Any opinions? Or ideas?

    Thanks again for everyone's help.

  12. #12
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    After looking at the YouTube video that "Snilton" linked to...
    I saw another video that shows the raw output of a Piezo
    disk driving a Green LED.

    http://www.youtube.com/watch?v=Xuw9f...eature=related

    I now agree that perhaps the Piezo route would be easier than a
    Microphone and preamp to get a usable signal..
    Very simply... you could take the output of the Piezo and run the
    input LED of an Opto Isolator like a 4N26 or even a Triac output
    Opto Isolator like MOC3011... then control what you want with
    the output of the Opto Isolator of your choice...


    Jerry
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  13. #13
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    a piezzo will not power a LED which will easily consume 25mA, as the piezzo only outputs some microamps at max... true that you will perhaps reach some tens of volts, but that will not work

    trust that one, the circuit I've given will do the trick with a small alarm clock or toy piezzo, which you can tape under your membranes

    you just have to find someone to engrave the board for you if it's not possible for you to do it

    I can draw you a board on eagle if you want, it's quite easy, SMD or through hole, as you wish

  14. #14
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    Quote Originally Posted by shrad View Post
    a piezzo will not power a LED which will easily consume 25mA, as the piezzo only outputs some microamps at max... true that you will perhaps reach some tens of volts, but that will not work

    trust that one, the circuit I've given will do the trick with a small alarm clock or toy piezzo, which you can tape under your membranes

    you just have to find someone to engrave the board for you if it's not possible for you to do it

    I can draw you a board on eagle if you want, it's quite easy, SMD or through hole, as you wish
    Hey shrad...

    Did you not see the Video I linked to... It clearly shows 1 Green LED flashing
    in time with the tapping on a Piezo buzzer disk... I see no other
    components...
    The OP wants to detect the beats of the drum... and this idea seems to work...
    Am I missing something...

    BTW... your circuit looks like it will pick up all sound in the piezo's range with
    a lot more circuitry... to produce the same single shot response..

    The 1st stage is an amplifier and the 2nd stage is an average peak detector
    comparator..

    But I suppose either circuit will give you some results...


    Jerry
    Last edited by lasersbee; 10-12-2009 at 02:20.
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  15. #15
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    I'm not an expert with diode drivers or anything, but wouldn't you need some sort of voltage/current limiting circuitry before feeding a piezo straight into the +mod of the driver? surely if you really slammed that piezo it would make more than 5v, which some drivers might not be designed to cope with.
    Just a thought

  16. #16
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    Lightbulb

    What about a relay like this? :::

    http://www.allelectronics.com/make-a...RELAY/-/1.html

    That way the relay would deliver consistent voltage each time it's triggered.

  17. #17
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    A relay is very slow to react and output a signal compared to an electronic switch like a transistor...


    Jerry
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  18. #18
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    plus you'd need quite a big piezo to power up the solenoid insode it, they draw a relatively large amount of current

  19. #19
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    yup, sorry for the assumption that a piezzo couldn't drive a LED, I missed the word "correctly" in the sentence

    in fact the circuit I mentioned picks all the noise from the piezzo, amplifies it by a scalable factor, and then triggers on a scalable level

    the output being 0V or 5V low current from the opamp, it is best suited to attack the input of a modulation input or DMX input board without damaging it, and the scalable gain and treshold will allow to adapt it to any instrument, be it a trumpet or a giant tam-tam

  20. #20
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    Quote Originally Posted by lasersbee View Post
    I now agree that perhaps the Piezo route would be easier than a
    Microphone and preamp to get a usable signal..
    Very simply... you could take the output of the Piezo and run the
    input LED of an Opto Isolator like a 4N26 or even a Triac output
    Opto Isolator like MOC3011... then control what you want with
    the output of the Opto Isolator of your choice...


    Jerry

    So would the wiring diagram look something like this?

    (please correct me if it's wrong)
    Attached Images Attached Images

  21. #21
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    Yeah... that would be a starting point...
    You will of course need to experiment with it...

    If you are just driving TTL level circuits you would not need a Triac
    output Opto Isolator a Transistor Outpot OI would be better like a
    4N26 or similar...


    Jerry
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