drums and piezo sensors

[David Lee]

Martin,

I have used the latter piezo disks you describe with great success with
acoustic drums and a D4 drum module. The ones I get are about .5 inch
around disk with 2 leads already attached (cost...$0.10 US). 

To prepare the sensor for use I did the following:

(1) solder a 1/4 closed frame jack to the piezo's leads. 
(2) mount the sensor under the drum's impact head (i.e. the top one) with
some adhesive.
(3) mount the newly installed jack to the shell of the drum with some
velcro.
(4) Attach the trigger to the D4 with a standard guitar cable.

Some sensetivity tuning was needed on the trigger interface (...in my case
a D4) to get the inputs to fire correctly without any false triggers. Once
the trigger interface was tuned everything worked well and was inexpensive
to setup.

  I have often thought that a piezo would be good for making a trigger for
noiseless cymbals. This could be done by mounting a flat metal plate on the
cybal stands instead real cybals. With a trigger installed on the underside
of the plate this would now serve as a trigger for crash and ride samples.
Metal is a excelent trigger surface as it conducts impact vibration well,
but must be dampend when in use so it can't free ring (...like a marimba).
Unfortunately many drummers don't like playing tomm lines on metal plates.
But metal for triggering cybals would be acceptible as the real instrument
is made of metal. Each stand will hold only one trigger plate so the chance
of false triggers isn't realy a problem. The only possible problem I can
see is that the plate needs to be pretty rigid so it doesn't vibrate like a
cybal. I figure that the plate could be installed on a standard cymbal boom
and would simply need to be affixed well with the overhead mounting bolt so
it doesn't move around when struck. Basically we want the trigger to create
a quick spike (i.e. a "clink" or "ping") so we can accurately trigger the
sound device. 

If you wan't to order some piezo disk's for triggering check out the
following place:

http://www.goldmine-elec.com/

They sell a variety of piezo buzzers useful in making triggers.

----------
From: Martin Czech <martin.czech at intermetall.de>
To: synth-diy at mailhost.bpa.nl
Subject: drums and piezo sensors
Date: Thursday, June 25, 1998 10:38 AM

Someone wrote a nice mail about margarine containers as
diy-electro-drum trigger, and someone came up with the idea to use
rubber pads instead (mouse pads). Now, beeing in the little local
electronics shop, I saw a piezo sound transducer, a little black disk
with an opening on one side. I tryed it today with a sampling scope,
you can easily get voltages > 10V out of it. If you hit it with soft
material (rubber screw driver handle) the amplitude is low, but if you
hit it hard with a piece of metal... I think this is because the
resonant frequency of the piezo disk inside is about 2 kHz and it takes
a hard punch on the piezo plastic encapsulation to get sufficient
energy into this frequency band. This could help to separate different
sensors mounted on the same piece of wood etc. If they are damped with
rubber no "body" waves from the wood should have the necessary energy
in this frequency band, so crosstalk could be minimised. But the
plastic containment is still 4 mm thick, too much to simply mount it
between two mouse pads and the like. But beside this type of
soundtransducer I found the naked piezo element, looking like a very
thin (0.7mm) brass disk, about 4 cm diameter. One side is shiny brass,
on the other there is the silver electrodes, one can solder two wires
to them (not too hot, max 290C!). This piezo is even cheaper ($0.5) and
gives also a lot of amplitude. Maybe it is necessary to add some diode
clamping in order to protect the trigger inputs. However, these flat
piezos seem to be quite usefull as a trigger device.

m.c.

------------------------------------------------------------------------
m.c. has made it finally:  3 CDs out now; 72 min. minimum; "1"
(1994-1995),"2" (95-96),"three" (96-97); experimental stuff; mostly
Eimert/Stockhausen style; but also modern popular style