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What is Circuit Bending?
It's education through exploration. Circuit Bending is the art of modifying existing electronics, usually children's toys, guitar effects, inexpensive battery-powered musical instruments, etc. to create unique musical instruments. By adding additional electronic components, wire patches, switches, contact points, photo sensors, potentiometer... to control new connections within the device's pre-existing circuitry you can achieve higher interactive experimental levels of new voices.
 
Learning the Basics
Clock bending is a very common circuit bend that can be done to just about any battery operated toy. A clock bend involves finding the resistor that is in charge of keeping the speed for the clock constant, removing it and replacing it with a veritable resistor that you can control. You will then be able to adjust the speed of the clock hence changing the pitch of the sound lower or higher. A veritable resistor can be a potentiometer, photo sensor or body contacts (using the human body).
 
Dub Crusher Keyboard
Dub Crusher Keyboard Side View
 
Building the "Dub Crusher" Keyboard Circuit Bending Kit
Welcome to the wonderful wild world of circuit bending!
This kit will teach a beginning student the educational art of circuit bending.
 
Check Your Build Tools:
Batteries - 2 "AA" size
Soldering iron - 25-40 watt soldering pencil
Solder - rosin core 60/40 of .032 gauge
Desoldering braid, solder wick, or solder sucker
Wire stripper and clipper - sharp diagonal cutters
Drill and bits
Glue gun
Electrical tape or shrink wrap Screw drivers (small and medium), wrenches, pliers & safety glasses
 
Workspace Set Up:
Open table with lots of bright light or sunlight
Ventilation fan for nasty solder fumes
Remember to keep a wet sponge or cloth near by
 
Parts, Identifying the Kit Components, Time to Test, Problem:
Parts:
Toy keyboard
1M & 10M potentiometers
220K & 10ohm resistors
3 Miniature SPDT toggle switch
1/8" output jack
Two body contacts
2 knobs
LED (short lead is negative and the longer lead is positive) and holder
1M Photo sensor (short lead is negative and the longer lead is positive) and holder
Hook up wire
 
Identifying the Kit Components:
KeyboardKit Components
 
Time to Test, Problem?
Open the battery compartment by removing the screw/lid and place two "AA" size batteries inside the compartment. Re-screw down the lid and make sure the keyboard functions properly. Problem? before you continue, please contact me at contact@markdhoffman.com
Check This OutAfter testing REMOVE the batteries from the compartment.
 
 
 
STEP 1 Grab the Screwdriver:
1) Carefully remove the 5 screws holding the keyboard's back on and gently pry it off to open the casing.
2) Remove the speaker, circuit board and rubber contact keyboard trigger pad to separate the two halves. All the components should easily pull "UP" off and out of their housing and seating.
 
STEP 2 Explore the Circuit:
Here is how you become educated in the art of circuit bending. Look over the circuit and become familiar with it, time to set out and explore!
Start by searching the circuit to find electronic components that react to changes in their resistance. How you ask?
 
Gum Drop ICPitch ResistorFind the "BRAIN" for the circuit, usually a black blob. This blob is a cheap form of integrated circuit (IC). These are also called "gum drop" ICs. An IC is a collection of microscopic electrical components working together to perform complex functions... like making sound.
 
Once you've found the "BRAIN" on the circuit board, look for the resistor placed closest to it. Nine out of ten times this will be your pitch resistor. Test your theory by touching the leads of the resistor with your moist finger while the circuit is making sound. If you're right, the pitch should jump up or down. Yeah, you've found your 1st circuit bend!
The voltage from the two batteries is low enough to not give you a shock. Which brings up the highest rule in circuit bending, NEVER attempt to circuit bend a toy or electronic product that plugs into the wall or that uses a wall wart transformer, really anything that does not use batteries is off limits until you are more advanced!
 
STEP 3 Desoldering Pitch Resistor:
Removed Pitch ResistorPut on your safety glasses. After you have located the pitch resistor desolder it from the circuit board. A desoldering braid, also called a desoldering wick, is a braided cord of very small gauge wire. It removes solder through capillary action, the same process that causes water to "climb" up a paper towel. Unspool some of the desoldering braid and pull the braid apart by holding it tight and pushing it together to make it wider, then pull it straight. Place the end of the braid over one of the pitch resistor's solder points you want to desolder, and hold it in place with the soldering iron so that the braid is sandwiched between the iron and the solder point. When the braid heats up, the solder will melt and flow into the braid through capillary action. Remove the braid and iron as soon as it has soaked up the solder. Again do this same procedure to the other solder point on the pitch resistor. The pitch resistor should now be free and can be removed from the circuit board. Again, clean the solder points with the desoldering braid.
 
 
STEP 4 Soldering Pitch Wires:
Solder In WiresSolder two wires, 5" in length where you have just removed the pitch resistor. Use a soldering iron that is in nice shape and has a well-maintained tip. Remember to keep the tip of your soldering iron clean (tinned) with a little melted solder and keep a wet sponge or cloth near by to wipe the tip with before you solder. When soldering heat the part and the joint at the same time then push the solder into the joint and it will flow to the heated points.
 
 
 
 
 
STEP 5 Installing Peak Buffering Trim Resistor:
Peak Buffer ResistorPeak Pitch Buffer ResistorIt is of utmost importance when installing a pitch adjustment bend that you install a peak buffering trim pot and or a resistor. A buffering trim resistor will limit how high and low the pitch can go. In some cases no buffer is needed at all, but this is very uncommon.
I usually use a potentiometer to find the correct high end buffering value, then replace the pot with a resistor or trim pot for fine-tuning.
 
Solder the 220K resistor to the middle terminal on the 10M potentiometer. It does not matter what end of the resistor you solder to the terminal.
 
 
Check This OutA peak buffer on the high end is most important. Turning the pitch too high for too long can burn out the circuit. Sometimes turning the pitch too high for just a second will fry it.
 
 
 
STEP 6 Drilling the Enclosure:
Examine the enclosure closely to determine where the most logical open areas are to add in additional electronics(I've already done this for you but check it out anyway you might want to make your's a bit more custom). In some toys there will not be enough room and perhaps a break-out box would be necessary to add on giving you that extra room you need.
Check This OutBe careful that when adding in the additional electronics that the enclosure can be properly screwed back together. Watch out for the battery box and where it sits in the toy. I've done this before where on one side of the enclosure there is a nice open area. But found out that when I attached the other side of the enclosure back together I was adding components where the battery box sits from the other side of the enclosure. Test this by placing the electronics in the enclosure before drilling the holes and seeing how they will fit with the other side in place.
 
 
You'll need to drill seven large holes and two small holes. 3-holes for the miniature SPDT toggle switchs, 2-holes for the potentiometers, 1-hole for the LED, 1-hole for the photo sensor and 2-holes for the body contacts.
 
Drilling the Enclosure
Drill in the bottom side of the enclosure three holes, one for the photo sensor holder, one for the 10M potentiometer and one for the output jack.
 
Mount the photo sensor in the middle of the top tip of the enclosure by glueing it in place
 
Mount the 10M potentiometer next to the side of the enclosure
 
Mount the output jack in the corner next to the side
 
 
 
 
 
Photo Sensor SwitchOn Off SwitchBody Contacts
 
Drilling the Enclosure
Drill in the top side of the enclosure three holes for the miniature SPDT toggle switches, one for the LED holder and one for the 1M potentiometer.
 
Mount the photo sensor on/off switch in the middle of the side of the enclosure
 
Mount the unit's on/off switch in the middle of the side of the angle of the enclosure, near the lower section
 
Mount the bit crusher on/off switch close to the edge & close to the 1M potentiometer on the angle of the enclosure
 
Mount the LED holder & LED under the unit's on/off switch next to the speaker housing by glueing it in place
 
Mount the 1M potentiometer next to the side of the enclosure and next to the screw support
 
Mount the body contacts by glueing them to the enclosure
 
Photo Sensor SwitchOn Off SwitchBody ContactsLED Holder SwitchBit Crusher Switch
 
Aditional Photos of the Outside:
Bit Crusher SwitchBody ContactsBody ContactsPhoto Sensor Switch
 
STEP 7 Wiring the Circuit:
Photo of the insides to reference the wiring
Inside Wiring
1) Starting with the photo sensor find the short lead (negitive lead) and solder a wire to it and wrap this connection in electrical tape or shrink wrap it. This wire then is soldered to the middle terminal of the 10M potentiometer the same place where you soldered the pitch buffer resistor (white wire in photo).
 
Solder a wire to the long lead (positive lead) on the photo sensor and wrap this connection in electrical tape or shrink wrap it. This wire is soldered to the end terminal of the photo sensor on/off switch (white wire in photo).
 
2) Moving on to the photo sensor switch, solder a wire to the other end terminal and run that connection to the end terminal on the 10M potentiometer (purple wire in photo).
 
Solder the wire that was added to the circuit board in place of the resistor we removed to the middle terminal of the switch (purple wire in photo).
 
3) Moving on to the 10M potentiometer, solder a wire to the end terminal and run that connection to the end terminal of the 1M potentiometer (purple wire in photo).
 
Solder the wire that was added to the circuit board in place of the resistor we removed to the pitch buffer resistor (red wire in photo).
 
4) Moving on to the battery box, desolder the black and red wire. Solder a wire to the negative side of the battery box and run this connection to the end termainal of the bit crusher switch (black wire in photo). There will be three wires attached to the terminal so leave room enough for all three (black wires in photo).
 
Solder the black wire you desoldered from the battery box to this same end terminal (black wire in photo).
 
Solder another black wire to this same end terminal and run it to the short end of the LED (negative lead) (black wire in photo). Wrap this connection in electrical tape or shrink wrap it.
 
Solder a wire from the positive side of the battery box to the end terminal of the Dub Crusher on/off switch (red wire in photo).
 
5) Moving on to the Dub Crusher on/off switch, solder the long lead of the LED to the middle terminal of the switch (red wire in photo).
 
Solder another wire to the middle terminal and run this connection to the red wire that was removed from the battery box (red wire in photo). Wrap this connection in electrical tape or shrink wrap it.
 
6) Moving on to the bit crusher switch, solder a wire to the middle terminal and run this connection to the middle terminal of the 1M potentiometer (white wire in photo).
 
 
7) Moving on to the body contacts, solder a wire to each contact (white wires in photo).
 
Solder one wire from a contact to the end terminal of the 1M potentiometer (white wire in photo).
 
Solder the other wire from the contact to the middle terminal of the 1M potentiometer (white wire in photo).
 
8) Moving on the output jack, desolder the two blue wires from the speaker and solder a black and red wire 3" in length to the speaker (black and red wires in photo). Use this photo below as a wiring diagram to complete the circuit.
 
Wiring the Output Jack
 
STEP 8 Packing it Back into the Enclosure:
Be extra careful when bending the wires! Place the speaker back into it's holder, place the rubber contact strip back into it's holder and position the circuit board over the top of it. Then screw on the back and start Dub Crushing!!
 
STEP 9 Crushing the Tones, Not Working? De-Bug Testing:
Crushing the Tones:
1) Push the trigger buttons on the "Dub Crusher" keyboard
2) Crank the pitch bend knob - make sure the high pitch buffer is functioning perfect and the low pitch can crush the tone to bit level
3) Flip the switch and test the body contacts
4) Test the output jack with an external battery amplifier
 
Not Working? De-bug Testing:
Batteries in the compartment
Check the wires crossing over going to the battery pack
Did the testing go OK until you screwed the back on? Check for a pinched wire or a loose wire not completely soldered to a connection point
 
If you still have a problem, please contact me at contact@markdhoffman.com
 
 
Copyright 2010-2014 Mark D. Hoffman. All rights reserved.