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Home DIY DRUM TRIGGER PAD
ASSEMBLIES
(VARIOUS TECHNIQUES) - Original Article by John Green
From: jgreen@bogey.pd
Date: 31 Oct 1994 19:38:32 GMT
This is a description of my experience constructing a drum trigger
following instructions I got from some kind people here.
- Went to Radio Shack (Tandy) and bought 2 piezo speaker elements
($1.99 each).
- Connected the two wires to a 1/4 inch cable.
- Plugged the cable into my D4.
- Placed a mouse pad on the piezo.
It worked perfectly. I could play any of the 500 sounds, send MIDI data
out from the D4 and record it. No adjustment of the Trigger attributes on the D4 required.
Velocity sensitive.
Now I'm going to build an Octapad of sorts with 8 of these mounted on a
board, somehow isolated from each other. I'm also going to experiment with different
thickness' of pad, etc.
Mail if you want more info.
Note: the remaining entries on this page were collected together in
an archive and appear to have been garbled at some point. I've tried to reconstruct it
from two separate sources. Apologies for any remaining glitches. If anyone has a copy of
this material intact, please let me know.
From: alighton@dale.cts.com
Date: Wed Aug 12 08:47:11 1992
I have a Roland Octapad and wanted to build some triggers for the extra
inputs. I bought the radio shack piezo buzzers and built some pads that have worked real
well. I'm sure they would work equally well with the D4. For the Toms and snare, I bought
Remo practice pads. They are made of grey plastic, have a regular drum head on them and a
pseudo tensioning ring. They are about 2" thick and are filled with soft foam rubber.
I mounted the piezo buzzer to the underside of a .06 thick circular aluminium plate with a
slightly smaller diameter than the inside of the practice pad, and then cut away most of
the foam rubber in the drum pad so that the plate rests on a foam shelf around its
perimeter. The foam looks like a foam ring, with a cross section like this:
Sorry Diagram Missing!
With the aluminium plate cradled in the foam ring, there is very little
chance that hits on adjacent pads can trigger the sensor. I then fill the gap between the
plate and the underside of the drum head with a sheet of foam rubber (I used the pads that
are for muting drums, wet suit material would work GREAT, so would your basic mouse pad).
Drill a hole for the cable to come out, assemble the whole thing, and it works GREAT and
doesn't look bad either. They sell these pads in 6", 8", and 10" diameters.
They come with a mount on the underside, so they are easy to mount. The stick response is
very much like a real drum, and is a little adjustable for your liking. Total cost to
build one is between 27 and 35 dollars, depending which diameter pad you buy. For Cymbals,
I used Dog Frisbee's (made of rawhide)! I tried plastic Frisbees but they don't hold up. I
mounted one of the sensors to the underside of the Frisbee using silicone rubber (use the
stuff made for electronics, the other has acetic acid that will destroy electronics).
For the bass drum, I bought a regular pedal, but made it so the beater
was beating down against a horizontal surface instead of against a vertical surface. I
encapsulated a piezo buzzer in a rubber/steel motor mount from some kind of car, and made
a wood block to hold it where the beater on the pedal can hit it. Total cost was about 80
bucks including the Premier bass drum pedal. Any kind of bass drum pedal will work as long
as the beater attaches to the pivot shaft with a separate clamp from the chain or belt
that drives the shaft from the pedal. If it has an integral clamp for both the beater and
the drive attachment, it means you have to find a way to hold the sensor vertically in
front of the beater like a bass drum head, making matters far more complicated.
I built a space frame to hold all this shit out of PVC irrigation
tubing (use schedule 40, 1inch or larger). The entire frame cost less than 35 bucks, and
uses hose clamps and mounts made from PVC elbows with epoxied in bolts to hold the drum
pads/cymbals. I admit, it sounds hokey. But the whole thing works great and was WAY
cheaper than buying all this stuff. It seems to be taking the beating and holding up just
fine.
here is some more: I am using an Octapad I, not the later units. There
is all kinds of sensitivity adjustments, they generally need to be set fairly sensitive.
The key to no false triggering from adjacent hits is mechanical isolation. That's why the
metal plate is suspended in a foam cradle.
The key to increasing the sensitivity of the piezo thing is to have it
in intimate contact with a larger metal plate. The metal plate will conduct vibrations
from a considerable distance to the crystal. You ARE removing the piezo thing from the
housing, aren't you? You HAVE to at least remove the bottom cover of the housing (which is
the back side of the little circuit card, DON'T break it!!) and flip the sensor upside
down in the housing, and pot it flush with 5 minute epoxy. You MUST have vibration through
a solid medium transmitted directly to the little brass plate that the sensor is mounted
on, and the more "solid" the medium is the better. For instance, 5 minute epoxy
works better than 24 hour epoxy because it is more brittle and has a lower damping
constant. Except for on the "cymbals" (dog Frisbees), I always remove the entire
piezo assembly from the black plastic housing and glue the whole shabang to an aluminium
plate. WAY increases the sensitivity.
The way false triggering from adjacent pads is achieved inside the
Octapad is through some active sensing circuitry. A couple extra piezo sensors are
attached to the metal frame of the Octapad. When you hit a pad, it only transmits the
difference signals between the hit pad and the frame sensors. I guess that assumes that
vibrations on an adjacent pad and the frame would be approximately the same, so no signal
would be transmitted from the adjacent pad. But the hit pad would have a way larger
amplitude hit, so a trigger would occur. The Alesis D4 actually has variable parameters
for controlling the sensitivities of the difference signals.
If you are using a bass drum pedal, take a toilet paper tube, cut it in
half so it is only about 2 inches long or so. Tape up the bottom hole. Attach more rugged
wires to the very fine leads on the piezo buzzer. Fill the tube halfway with epoxy. Drop
in the sensor, make sure the wire joint is down in the tube somewhat. Continue filling the
tube almost to the top. 5 minute epoxy will probably be too exothermic for this, you
better use 30 minute epoxy. Let the whole thing cure. Build a block of wood that will hold
this tube of epoxy. I suggest wiring a 1/4" phono jack and mounting it to the piece
of wood. I used a Stratocaster jack plate for this. Design the block of wood so that the
bass drum clamp can clamp on to the piece of wood in such a position that the bass drum
beater will beat on the end of the tube of epoxy. This will be easier if you have a bass
drum pedal that allows the beater to be rotated on the pivot shaft relative to the pedal,
so that the pedal is not beating against a vertical bass drum.
Al Lighton
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From: js0998%future@uunet.UU.NET (Cam Spillman)
Date: Fri Aug 14 11:05:44 1992
I built mine using quarter-sized flat piezo buzzers. I made a trigger
pad substrate of 1/4" particle board, then put a layer of closed-cell foam (like
mouse pads or wetsuit mat'l) about 1/4" thick, then rubber strike-surface I got from
a friend who works in a belt-rubber factory, about 1/4" thick also. I made a hole in
the closed-cell layer as big as the trigger and mounted it with rubber cement about
halfway in. These seem to work well, and false-triggering is kept to a minimum by
isolating the piezo from both the strike surface and the base surface. So if I hit other
pads on the stand it doesn't propagate vibrations through to the other units, and when I
hit the strike surface I have some dampening in the foam layer to keep it from
overloading. This may not be the only way to do it, but it was the way that worked given
information I got from Electronic Musician mag, circa 1989 (?) and the materials I had on
hand.
For what it's worth, I made a really funky hi-hat assembly with one pad
mounted on a hi-hat stand, one pad sandwiched between foam underneath the pedal. The top
pad is *open* and the bottom trigger is *close*. Oddly enough, it seems to work OK and
doesn't overly offend my drummer friends (they are a little shocked but appreciate the
insipid simplicity of the design). Good Luck!
Cam
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And now for some of my own experiences: I used several different kinds
of buzzers. The best ones were model number 23-073. Cheap ($1.49) and simple to break out
of the plastic case. Avoid all three wire piezos. The third wire is connected to a
separate element, which is used to provide a feedback signal for your basic
oscillator/speaker circuit. This third element was definitely the cause of the false
triggers in my original set-up - using two wire piezos cured the problem. I glued the
triggers to aluminium plates (found in the trash) using epoxy - this trick really improved
the signal level and overall response (thanx Al!).
For a bass drum, I made a right angle out of wood and purchased a bass
drum pedal (39$, used) I covered the metal plate with some foam, put some softer foam
behind it and screwed it to the wood. The original wood piece was too resonant and caused
some false triggers, so I nailed a second piece of wood to the back of the first, which
increased the mass enough to stop the vibrations. The other triggers are currently resting
on top of blocks of foam on a table. Next step is to build a PVC rig to hold them. I need
better stuff for the impact surfaces, as the foam I have is not bouncy enough, but I have
located a big warehouse distributor, and I'm sure it will be no problem. So I now have a
12-note Octapad instead of an 8-note. Makes life much happier. hope this helps.
cliffw
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