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MoofTronic Mini Synth 

Make] Projects 

MoofTronic Mini Synth 

Written By: Brian McNamara 



Diagonal pliers (1) 

Resistor (1) 

Hot glue gun (1) 

Voltage regulator (1) 


70-92 package 

Needlenose pliers M) 

Picaxe-08M 8-pin microcontroller (1) 

Soldering iron (1) 

SparkFun Electronics part . 

IC socket (1) 

Battery (1) 

• Battery clip (1) 

RadioShack #270-324 

Mini speaker (1) 

removed from a pair of headphones 

Stereo jack (1) 

Insulated wire (2-3') 

Heat-shrink tubinq (1) 

Cable ties (1) 

aka zip ties 

Picaxe serial programming cable (1) 

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Pagel of 9 

MoofTronic Mini Synth 


I was playing around with a Picaxe microcontroller one day, trying to make a little keyboard. 
I wanted to build an absolutely minimal hardware frame that I could put together quickly 
without a circuit board. The result was the MoofTronic — a small electronic instrument built 
on a 24-pin IC socket. To play 8 different notes (1 octave in the key of C) against a fast- 
modulation drone, you touch a stylus to 8 legs of the socket. It also has a small antenna that 
you can touch to add an effect to the note being played. The 8-pin Picaxe microcontroller 
that runs the software and generates the sounds sits in one end of the socket and has a 
small speaker mounted on top. A programming port allows you to easily debug and test new 
sound-making programs. 

Step 1 — Fit the 8 resistors to the IC socket bottom. 

• The 8 resistors form a ladder of 
increasing resistance that allows 
the socket pins to play different 
notes. Start the ladder by bending 
the legs of the 1 K resistor around 
pins 12 and 13, leaving enough 
wire on one end to join pin 13 to pin 

• Trim excess wire and repeat down 
the socket, joining pin pairs with 
the 2.2K, 3.3K, 4.7K, 12K, 22K, 
33K, and 39K resistors, in order. 
No jumper is needed between pins 
20 and 21. Finally, solder the 
resistors in place. Download the 
schematics PDF under Files 

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MoofTronic Mini Synth 
Step 2 — Add the voltage regulator. 

• Trim pin 3 of the 78L05 voltage 
regulator to about 1/8", then solder 
it to the red wire of the battery clip 
and cover the joint with heat-shrink 

• With the 78L05 facing up, bend 
pins 1 and 2 out at right angles, pin 
1 to the left and pin 2 to the right. 
Positioning the regulator flat within 
the socket, bend pin 1 around the 
IC socket's pin 1 and bend the 
regulator's pin 2 around the 
socket's pin 24. Trim the wires, but 
don't solder yet. 

Step 3 — Wire the link and 10K resistor. 

• Solder a wire diagonally from pin 1 to pin 20 of the IC socket. Connect pin 22 to pin 24 with 
a 10K resistor. Wrap the legs around the pins, but don't solder yet. 

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MoofTronic Mini Synth 

Step 4 — Add the stylus and antenna. 

• To make the stylus, strip and tin a 
5" length of wire and fit some heat- 
shrink over one end, leaving a bit 
of metal exposed. Solder the other 
end to pin 22 on the socket. 

• For the antenna, solder some 
leftover wire from a resistor leg to 
pin 3 of the socket, and bend it 
around to the top. 

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MoofTronic Mini Synth 

Step 5 — Add the program port. 

• Cut three 4" lengths of wire and 
solder 1 wire each to socket pins 2, 
23, and 24. Cut the wire from pin 2 
in half, and solder-splice a 22K 
resistor in the middle. Cover the 
resistor with heat-shrink. 

• Solder the wire from the 22K 
resistor to the ring (middle) contact 
of the 3.5mm audio jack, solder the 
pin 24 wire to the jack's tip contact, 
and solder the pin 23 lead to the 
sleeve (inner) contact. 

• Solder a 10K resistor between the 
tip and ring contacts of the audio 
jack, and reinforce the connections 
with 3/8" heat-shrink. Finally, 
bundle the programming port and 
battery clip leads together with 2 
cable ties. 

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MoofTronic Mini Synth 

Step 6 — Fit the Picaxe microcontroller. 

• Fit the Picaxe-08M into the 24-pin 
IC socket. Pin 1 on the Picaxe 
goes to pin 1 of the IC socket. 

• Note: I used a 12.7mm 
(0.5") wide socket, so I had 

to bend the Picaxe pins slightly. If 
you use a 10.16mm (0.4") wide IC 
socket, you don't have to bend the 
IC socket pins, but it's a bit harder 
to fit the resistors. 

Step 7 — Add the speaker. 

• I used an old in-ear headphone 
speaker, so the first thing was to 
disengage it from the surrounding 
plastic. Glue the speaker onto the 
Picaxe, and add a bit more glue 
where its delicate little wires attach 
to the speaker coil. 

• Cut the speaker wires to about 1" 
and solder one to socket pin 24 and 
the other to pin 21 . Solder the black 
(-) battery wire to socket pin 24, 
and reinforce the socket ends of 
the headphone wires with more 

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MoofTronic Mini Synth 

Step 8 — Program the microcontroller. 

• Download and install the Picaxe Programming Editor software, free from http://www.rev- . 

• Then download the mooftronic.bas program file from . 

• Connect the serial cable from the computer to the programming port on the MoofTronic. 
Launch the Picaxe Programming Editor. Select File — > Open, then open the file 
mooftronic.bas from the folder you downloaded it into. 

• Power up the MoofTronic by connecting the 9V battery. Now load the program onto the 
MoofTronic by clicking Picaxe — > Run. You'll see a dialog box with a progress bar while 
the program is loading. This takes only a few seconds. Then a second dialog box will tell 
you that you have successfully programmed the Picaxe. 

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MoofTronic Mini Synth 

Step 9 — Test and glue. 

• Fit the 9V battery into the battery 
clip, and test that the device works. 
Start making noise with the 
MoofTronic by touching any pin 
from 5 to 12 of the IC socket with 
the stylus. If you also touch the 
small antenna with your finger, the 
pitch of the sound changes, and 
quickly goes up and down. 

• Once it's all working correctly, fill 
the bottom section of the IC socket 
with glue from the hot glue gun. 
This stabilizes all the little wires 
and keeps them from breaking off. 

Step 10 — Go nuts. 


-f-r .., 

' . 1 



^^^^ ^r^ 

• One of the best things about the 
MoofTronic is that the software can 
easily be changed, reprogrammed, 
and tested on the hardware in a 
matter of minutes. So once you've 
built the hardware, go crazy 
hacking some new sounds! 

This project originally appeared in MAKE Magazine Volume 15 . 

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MoofTronic Mini Synth 
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Weekend Project: MoofTronic Mini Synth 

http:/ / 

last generated on 2012-11-03 04:22:35 AM. 

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