mounting homebrew contact mic

[Tom Polokonis]

A while back I bought a couple piezo buzzers with no intention of using
them.  They were 50 cents a piece and totally flat.  They have no casing to
cut away, which is a plus.  Anyway, I later bought a dean markley piezo
guitar pickup for SIXTY DOLLARS!  I have just found out with the help of
this discussion that I wasted a lot of cash.  The expensive pickup, if it
works better at all (I can't hear much difference), sure doesn't sound
fifty-nine dollars better. Warn your friends!
Also, this way, you can cover the instrument with the things.  They ought to
work for everything but a singer and of course, a synthesizer. Instructions
for mounting them on/in a guitar can be found at
http://www.harmonycentral.com/Guitar/piezo-pickups.txt  I personally intend
to buy a load of them and hot glue them to various objects. for example,
i've got a cheap electric bass which has a hollow body (no sound holes, it
looks normal on the outside).  I'm going to weigh it down with these things
to make up for its one pickup.  Well, have fun and may you never be ripped
off.
-Tom
-----Original Message-----
From: Barry L Klein <Barry.L.Klein at wdc.com>
To: synth-diy at mailhost.bpa.nl <synth-diy at mailhost.bpa.nl>
Date: Monday, September 13, 1999 9:54 PM
Subject: RE: Re: Re: mounting homebrew contact mic


>Another approach to this could be to use coaxial cable with a kynar
>insulation which has the piezo-electric properties to act as a contact
>pickup of sorts.  This material is commonly used as car sensors for
>traffic lights.  And I saw some of it being used as mics for violins and
>basses at the NAMM show.  I just haven't tried making something up on my
>own, other than a basic shock sensor hooked up to one of those in-shoe LED
>circuits.
>
>Barry
>
>----------
>From: CCartCat at aol.com[SMTP:CCartCat at aol.com]
>Sent: Sunday, September 12, 1999 10:30 AM
>To: synth-diy at mailhost.bpa.nl
>Subject: Re:  Re: mounting homebrew contact mic
>
>The $1.49 piezo has a deeper plastic case (I got both just in case or
>whatever).  So the wadcutter doesn't *just* protrude from the face of that
>
>piezo (as it does when glued into the other piezo).  It's too short to
>protrude at all.
>
>I tried gluing one wadcutter on top of the other.  Kinda tall--protrudes
>more
>(too much?).  Haven't glued the doubled wadcutter to the $1.49 piezo yet,
>so
>this is all guesswork and no experience ;-) , but you might try the
>doubled
>wadcutter.  Use the putty/blue goo/beeswax/adhesive to both hold the piezo
>to
>the object mic'd and to shim the difference.  Or glue something solid and
>appropriately sized onto the wadcutter to extend it about an 1/8" beyond
>the
>piezo case surface.  (After all, wadcutters come in a box of 250.  So you
>can
>experiment with them--or take up shooting.)
>
>And if you spring for the $1.79 piezo, you'll can build that and then
>compare
>& contrast the $1.49 options to the original design.  Or do an exchange
>for
>the $1.79 and remove all doubt. (I've opened the blister pack on mine, am
>curious, have approx. 240 wadcutter pellets on hand--thus, I'm committed.)
>
>Hope this OT blather helps,
>Kevin
>
>
>In a message dated 9/10/99 11:58:36 PM, Harry B. wrote:
>
><<Hell... give it a try...
>
>Essentially they are similar. The two wire unit is all you require... The
>three
>wire unit has a little "feedback" strip that is used with a single
>transistor
>to
>make an oscillator (the main element (speaker) vibrates and the little
>element
>picks it up (mic) and the transistor amplifies it... and because the piezo
>has
>mass and stiffness (and is mounted at the nodes) it has a natural resonant
>frequency and oscillates there...
>
>I've used both kinds...
>
>search for MuRata Erie (or someting like that) they manufacture all these
>devices...
>
>And it doesn't have to be a wadcurrer pellet, any small weight would do
>something... experiment... BB, lead shot... solder ball... whatever.
>
>"Hell its only money"   :^) Harry
>
>P.S. I got the 273-064 (just went downstairs and looked....)
>
>PPS. The pellets are Beeman H&N Match wadcutter pellets cat # 3011
>(but for heavens' sake use whatever you can find....)
>
>Christian Oncken wrote:
>
>> Well, I went to radioshack today... I forgot to take the part# with me,
>so
>> after much headscratching and deliberation, I came home with a different
>> model than the one described in your email.... its part# 273-073a,
>'piezo
>> transducer' $1.49.  it says 1500 to 3000hz...
>>
>> I think I did see the 273-064 part... it was $1.79 just like you said...
>but
>> it was labeled 'piezo buzzer' or something like that, I dont know if
>there's
>> a difference...
>>
>> Still havent got the wadcutter pellet yet...
>>
>> But anyway, since I got the wrong part, can you tell me if this one will
>> work?  Or would you suggest taking it back for an exchange on the right
>one?
>>
>> Any suggestions, ideas or advice you can give me would be greatly
>> appreciated.  I'm new to this stuff... Any web resources for this kind
>of
>> thing?
>>
>> thanks for all your help.
>>
>> Christian Oncken.
>>
>> >Yes... airrifle pellet... very light (as pellets go) and has a flat
>nose so
>> it
>> >is easy to glue reliably...
>> >
>> >The piezo as a driver will probably not have enough "balls" to drive a
>> spring,
>> >esp at low frequencies... I'd use a iron spring (or iron rod... pipe
>etc)
>> ir for
>> >a small spring, a ferrite bead... and drive with an electromagnet
>driven
>> from a
>> >stereo amp... Get enough turns so you don't fry it...
>> >
>> >Slinkies make good springs... if you put a magnetic pickup on a few
>> stretched
>> >slinkies, and then KICK it it makes a wonderful explosion...  "Yes"
>(the
>> band)
>> >shared that idea during a soundcheck during the "Relayer" tour... used
>in
>> "The
>> >Gates of Delirium"... Its like kicking a spring reverb but much BIGGER
>!!!
>> >
>> >Christian Oncken wrote:
>> >
>>>
>
>
>