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Electronic Drum Kit 

Makej Projects 

Electronic Drum Kit 

Written By: Tom Zimmerman 


Diagonal cutters (1) 
Drill (1) 
Eraser (1) 
Flat filed) 
Marker (1) 
Multimeter (1) 
Sandpaper (1) 
Screwdrivers (1) 
Soldering iron (1) 
Wire stripper (1) 


Vinyl tubing (1) 
Polyethylene tubing (1) 
Heat-shrink tubing (1) 
Foil tape (1) 
Bottle stoppers (4) 



Lag screws (6) 

Guitar strings (2) 

Guitar tuning pegs (2) 

insulated wrapping wire (1) 
Serial extension cables (2) 
Cable ties (12) 

Foam pipe insulation (1) 
PVC pipe (2) 
Wood (2) 
Bolts (2) 

Zoom MRT-3B Micro RhythmTrak drum 
machine (1) 

Dual general-purpose IC PC board (1) 
CD4066 quad CMOS switch (2) 
Socket (2) 

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Project enclosure (1) 

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Electronic Drum Kit 

Momentary push-button switch (1) 
Resistor (10) 
Capacitor (8) 
Silicone sealer (1) 


An electronic drum is basically a switch that triggers the playback of a digitally recorded 
drum. Here's how I built tubular drum controllers out of PVC pipe and connected them to a 
studio drum machine to create a professional-sounding electronic drum kit. Each controller 
has a guitar string suspended above 4 strips of aluminum tape. When you strike the string 
with a drumstick, it touches the tape and closes a circuit to trigger the corresponding sound 
from the drum machine. Foam covering the pipe softens the blow and provides a nice 
bounce. Underneath each controller, a pressure-sensitive piezoelectric device lifted out of 
the drum machine detects the force of the hit, to determine the relative volume. 

The brief contact between the struck string and the foil is too short for the drum machine to 
detect, so a pulse-stretching circuit lengthens the signal, by charging a capacitor. Two male- 
to-female serial cables let you unplug the controllers from the drum machine. I cut the 
cables in half and connected them to the controllers and the drum machine. To plug-and- 
play, you simply mate each connector to its former other half. 

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Electronic Drum Kit 

Step 1 — Build the controller bodies. 

• Note: Our Zoom MRT-3B drum machine has 7 trigger pads and 1 bank select 
switch. We'll make 2 controllers to drive it, each with 4 pads. For simplicity, I 
describe building 1 controller; just double each step to make both. The controllers are 
physically identical, but we'll wire them slightly differently later. 

• Draw a reference line straight down the PVC pipe; a doorjamb makes a good guide. Cut 
five 3" pieces each of vinyl and polyethylene tubing, then insert the polyethylene pieces 
into the vinyl pieces and thread a cable tie through each. These spacers will flank each 
drum pad. 

• Center a 30"x3" strip of foam over the pipe's reference line and secure it down with 5 
spacers, spaced 7" apart. Make sure the foam lies flat. Stick four 6" strips of foil tape to 
the foam, centering them between the spacers and avoiding wrinkles. 

• Orient the pipe left-to-right, the way you'll play it. Along the reference line at the left end, 
drill a 1/4" hole 1" from the end, and file a 1/16"-wide slot going 1/2" to the right. 


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Electronic Drum Kit 

Step 2 

• At the right end, drill a 1/4" hole 
along the line 1 1/2" from the end, 
and another 1/4" hole, for the 
tuning peg, on the far side of the 
pipe, 90° around from the line and 
3/4" from the end. Drill 1/16" pilot 
holes and install the tuning peg with 
the screws that came with it. Don't 
overtighten or you'll strip the 
threads. Drill a 1" hole near the 
upper left corner of each foil pad, 
outside the foam and next to its 
adjacent cable tie. 

• Mount the pipe to its base by 
turning it over and attaching the 
wood with 3 lag screws in 
countersunk holes. Solder a 6" wire 
to a guitar string's brass ring and 
slide the rubber stoppers, large 
ends pointing toward each other, 
onto the string. Pass the wire 
through the slotted hole in the pipe, 
and anchor it by sliding the brass 
ring under the slot. Feed the other 
end of the string down through the 
hole at the opposite end and thread 
it onto the tuning peg inside. Slide 1 
stopper to each end, and tighten 
the string so that it doesn't touch 
the foil. 

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Electronic Drum Kit 

Step 3 — Connect the pads. 

• Feed a wire through each of the 1/8" foil pad holes and out the left end of the pipe. Strip 3" 
of insulation off the pad-side wires, lay the bare copper along the edge of its foil pad, and 
tape it down with a 1/4"-wide strip of foil tape. 

• Note: The adhesive on the bottom of the foil is non-conductive, so the copper wire must 
touch the top surface of the pad foil. 

• Cut a serial cable in half. Take the female half and tie a knot 6" from the cut end. Use 
solder and heat-shrink tubing to connect the pad wires to the wires for serial pins 1 , 2, 3, 
and 4, as specified in the schematic diagram, available at 

http://www.makezine.eom/1 5/electronicdru... . Pads are numbered from left to right. Use a 
multimeter to associate the wires in the cable with the corresponding pins on the 

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Electronic Drum Kit 

Step 4 — Connect the piezo elements. 

• The Zoom MRT-3B drum machine has 2 pressure-sensitive piezoelectric elements that 
detect the force of pushes on its drum pad buttons. We'll remove them and put 1 
underneath each pipe, so that they'll perform the same function there. 

• Pry the volume knob off the drum machine and unscrew and remove the back of the case. 
Remove the 4 screws inside that hold the battery case and the 2 screws on the MIDI 
connector. Write down where they go, and save them in a cup. 

• The piezo elements are the disks behind the circuit board from the drum pad buttons. 
Unsolder both and gently remove them. Solder and heat-shrink two 36" wires to each, and 
thread the wires through the side pad hole near the middle of each pipe. Slip the piezo 
element between the pipe and the wood, but don't force it, or it will crack. Encase the 
entire piezo element and its wires in silicone sealer and let it set overnight. 

• Following the schematic, connect the piezo's red wire to serial cable pin 7 and its black 
wire to pin 8. Also connect the string wire to pin 9. This completes the controller's serial 
cable connections. Drill two 1/4" holes, one above the other, about 1/2" from the end of 
the pipe, and cable-tie the serial cable knot to the inside of the pipe. 

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Electronic Drum Kit 

Step 5 — Wire up the drum machine. 

i Push the power switch into the case to dislodge the top circuit board, then unfold it to 
expose the board underneath. Remove the remaining screws, lift the boards from the case, 
and remove the white silicone pad membrane from the board along with the buttons, pads, 
and display. Gently sand the carbon coating off the top right corner dot of the switch pad 
contacts to reveal copper pads. 

t Caution: Don't rub too hard or you'll scrape away the pads themselves. 


i Solder 12" lengths of 30-gauge wire to the right contact of each drum pad, and pairs of 
wires to the Pad Bank and Function switches. Replace the circuit boards in the case and 
thread the wires out the pad holes in front. Solder wire pairs to the power pads and to each 
of the piezo element pads on the back of the circuit boards and thread those out the front 
as well. Reassemble the drum machine in its case. 

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Electronic Drum Kit 

Step 6 — Build the pulse-stretching circuits. 

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Dnimi Pad 2 


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• Trim the mini PC board to fit in the project box. Clean its copper pads with a pencil eraser 
and solder a socket into the middle of each half. 

• Follow the schematic to build the rest: connect the controller wires from the serial cable to 
the quad switch's control pins (pins 5, 6, 12, and 13), hanging a grounded 470kQ resistor 
and 0.1 |jF capacitor off of each. Connect the quad switch's V+ (pin 14) to the controller's 
string (serial cable pin 9) through a 1kQ resistor. 

• Ground the specified quad switch pins. Finally, install both 4066 chips in the sockets. 

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Electronic Drum Kit 

Step 7 — Connect the drum machine. 

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Electronic Drum Kit 

• Bolt the project box to the drum 
machine, pass the male serial 
cables through 1/4" holes drilled 
in the sides, and strain-relieve 
them with cable ties. Mount the 
push-button switch on the side of 
the project box and solder it to the 
pair of wires from the drum 
machine's Function switch. 

• Follow the online schematic to 
connect the rest: solder the +V (pin 
14) and Ground (pin 7) of one of 
the 4066 chips to the V+ Power and 
Ground of the drum machine circuit 
board. Connect the pad button 
leads to the quad switches' signal 
pins. Connect the Pad Bank leads 
to pins 1 and 2 of controller #2. 

• Plug the 2 drum controllers into the 
circuit, and you're ready to play. 
The circuit gets its power from the 
drum machine, so you should see 
its LEDs light up when you hit each 
pad. If they don't, swap controller 
cables to determine whether the 
problem is with the controller or the 
circuit. Since we wired directly to 
the pads, all the functions of the 
drum machine will still work. Pad 5 
controls the Bank select. Strike it 
to select an alternate drum set. 

• Enjoy your electronic drum set. 
Bust out some beats and start a 

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Electronic Drum Kit 

This project originally appeared in MAKE Magazine Volume 15 . 

Related Posts on Make: Online: 

Red Rig Electronic Drumkit of Boldness 
DIY Electronic Drumkit System 
http://blog.makezine.eom/archive/2008/1 1 ... 

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