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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
External Trigger with Piezos
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bloodniece



Joined: Jun 20, 2005
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PostPosted: Mon Jun 20, 2005 2:15 pm    Post subject: External Trigger with Piezos Reply with quote  Mark this post and the followings unread

Hi,
I'm new to the list and am diggin' the tips and ideas. I want to trigger the SoundLab externally via piezos as a drum trigger. Ray has a schematic for audio signal to gate. Would this work for piezos? I want to avoid building something I can't use. (well, it does sound like fun to play guitar to trigger the gate)
Thanks
Derek

See photos of my Sound Lab here --> http://www.tanasfuck.com/soundlab/
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Afro88



Joined: Jun 20, 2004
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PostPosted: Mon Jun 20, 2005 4:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Haha, nice design! Cool Love the knobs, and the palm tree near the mixer is a nice touch Laughing

Sorry, I can't help with the piezo triggers...
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bloodniece



Joined: Jun 20, 2005
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PostPosted: Mon Jun 20, 2005 7:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks.
i might build the audio to trigger anyway. I imagine it'll work for piezos just fine.
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mosc
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PostPosted: Mon Jun 20, 2005 7:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

welcome Great to have you here.

The pictures of your Sound Lab are great. I love the look you have achieved. Very nice.

There are some good topics here with links to great piezo resources here on the forum. Try the search feature.

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opg



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PostPosted: Tue Jun 21, 2005 5:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Sounds a little like the drum trigger module my friend is building- which should be done this week! There will be plenty of pictures and possibly source code/schematics.

-8 inputs for acoustic drum triggers
-No annoying factory preset sounds
-Load and assign your own sounds, just like a sampler
-Force sensitive
-No MIDI
-Currently set up for 8-bit sounds, but 16-bit 44100 sounds may be possible in the future
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bloodniece



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PostPosted: Tue Jun 21, 2005 4:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Keep us posted on that project. sounds def.
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bloodniece



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PostPosted: Tue Jun 21, 2005 5:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
welcome Great to have you here.

The pictures of your Sound Lab are great. I love the look you have achieved. Very nice.

There are some good topics here with links to great piezo resources here on the forum. Try the search feature.


Thanks, I'll search away. I'm working on getting a PCB layout for the Audio Signal to Gate circuit. Anyone every used Osmond Quartz for PCB design?
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Mike Walters



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PostPosted: Tue Jun 21, 2005 8:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Maybe the piezo could activate the v-trig input? That's a transistor that just switches the manual gate (I believe). The voltage from the piezo to the base pin might be enough to cause the transistor to switch??
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bloodniece



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PostPosted: Tue Jun 21, 2005 9:30 pm    Post subject: Piezos redux Reply with quote  Mark this post and the followings unread

I tried to no avail with a commercial piezo trigger robbed from a drum set.
Perhaps not enough voltage to make the tranny to switch? As soon as I finish the board layout for the audio signal to gate I'll post it here and with Ray at musicfromouterspace
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jksuperstar



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PostPosted: Tue Jun 21, 2005 10:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

The current out of a piezo is extrememly small, you might want to through it through a buffer (like an LM324 or any other generic op-amp). You can hang a cap & resistor on it also, if the pulse out of the piezo is to short for a reliable trigger. Google the PAIA website, and search there for the thumb drum schematics...they should help.
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opg



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PostPosted: Fri Jul 08, 2005 10:32 am    Post subject: Reply with quote  Mark this post and the followings unread

jksuperstar wrote:
The current out of a piezo is extrememly small, you might want to through it through a buffer (like an LM324 or any other generic op-amp). You can hang a cap & resistor on it also, if the pulse out of the piezo is to short for a reliable trigger. Google the PAIA website, and search there for the thumb drum schematics...they should help.


This is very true. You really need to amplify the signal from a piezo trigger. Why, I once took a cheap Radio Shack piezo transducer and a 1/4" jack and plugged it into a mixer. I could could only hear anything if the gain and volume was way up.

I can check to see what went into the drum module...
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adhdboy



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PostPosted: Sat Jul 09, 2005 7:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi All

This sounds cool and I will try some experiments with this too. The round piezo elements that are about an inch across with a square crystal mounted on one side and two wires coming off would work great for this. Believe it or not they have the potential to emit hundreds of volts when they are struck but as has been stated here at extremely low currents. I suggest that you use a high impedance JFET op amp in a non-inverting voltage follower configuration and that you attenuate the output from the piezo with a resistor network so as not to damage the fet inputs on the op amp. The image gives a starting point for experimentation.

Cheers All


drum_trigger.gif
 Description:
A starting point for a drum trigger circuit using a piezo. I have not tried this but I will get out the breadboard and see what happens.
 Filesize:  7.52 KB
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drum_trigger.gif



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adhdboy



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PostPosted: Sat Jul 09, 2005 4:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have posted a drum trigger circuit that I got working today here:
http://www.musicfromouterspace.com/analogsynth/SOUNDLABMINISYNTH/drum_trigger.html

Enjoy

ADHDBOY

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Wild Zebra



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PostPosted: Mon Jul 11, 2005 7:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks thats pretty darn cool.
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Macaba



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PostPosted: Sun Jul 17, 2005 1:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

I was wondering, seeing as I have TL084's around here, if i could use that as the op-amp in the drum circuit?
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adhdboy



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PostPosted: Sun Jul 17, 2005 2:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sure they should work fine. The LF444 is just the standard op amp I breadboard with. Its just a low current version of a quad JFET op amp.
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Macaba



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PostPosted: Mon Jul 18, 2005 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks alot.

I'm starting AS level electronics this september, so by this time next year, hopefully i'll be designing my own synth circuits! Smile
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v-un-v
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PostPosted: Mon Jul 18, 2005 2:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Macaba wrote:
I'm starting AS level electronics this september, so by this time next year, hopefully i'll be designing my own synth circuits! :)


Well lets hope the extremely stale and dry lecturers don't dash your dreams to quickly ;) When I studied electronics- the teachers didn't know what to make of me, and especially didn't know what to make of electronic music.

An old friend of mine from Bristol had a really good time and his main tutor was very sympathetic. So I suppose it's luck of the draw.

best of luck anyhow :) I too am hoping to start a degree in 3D product design and Computer-aided product design in September- as a mature student- looks like a lot of fun :)
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Macaba



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PostPosted: Thu Jul 21, 2005 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

I have just breadboarded the final circuit on ray's page:

http://www.musicfromouterspace.com/analogsynth/SOUNDLABMINISYNTH/drum_trigger.html

And I'm so pleased! This is the first time a breadboard successfully worked first time, and so well too! (It is simple enough!).

Its beautiful! On my VCO, if I plug the cv into the exponental CV, then I can have any pitch dependant on strike impact, if i plug into the linear CV, i get a much more controlled impact change, you actually have to manual adjust the VCO to a start pitch and the piezo makes it jump slightly, a cool sound.

I want to learn about OP amps, and this circuit looks like a good example, so i'm gonna go though how i think it works and someone knowledgable can correct me.

1. The resistors accross the piezo are to reduce the voltage from hundreds of volts to something more managable.

2. The first op-amp simply amplifies the current as much as it can. (Not sure of the gain on the TL084 i used, anyone know?)

3. D1 is to stop C1 from discharging in the wrong direction.

4. The R5 and C1 combo is to provide a Release ramp, so to speak.

5. Then op amp B is to amplify this signal again.

6. Going to the trigger section, R7 and C2 is to make the pulse last a minimum interval so that the trigger can be detected by the circuitry in a synth? - This is a bit iffy, not sure about this.

7. Op amp C amplifies again (why all this amplification?)

8. Not sure why C3 and R8 are there.

9. The 2 resistor and cap arrangment attached to pin 13 is to only switch on the OP amp for a slight amount of time to make a proper trigger pulse?

EDIT: I've just read ray's description more carefully. Seems i'm wrong on most counts.

Thanks for anyone who helps.
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