Scratching records is loads of fun, even if you're not a turntablist. Don't you wish you could drop phat beats and scratch wherever you go? Well now you can; be a DJ Hero with wristwatch turntables!

Using 2 recordable greeting cards and some potentiometers you can record your own song, beat or sample, then playback and distort the sound to make your own music. These turntables are so small that you can strap to your wrist, making you the life of the party no matter where you go!

This project will cover the steps I took to make these specific sound turntables. New sounds can be recorded, and alternate greeting card styles(boards) can be substituted easily.
Feel free to remix and modify any of the circuit bending shown in this project to create your own unique turntables.
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Step 1: Tools + Materials

tools:

soldering kit
hobby knife
sandpaper
glue gun
marker

materials:

recordable greeting cards / pre-recorded greeting card
hobby box
2 x potentiometers (value varies)
small plastic pucks (I used furniture movers)
old wristwatch

Step 2: Audio Greeting Card

The electronics inside the audio greeting cards are pretty awesome. There's a huge variety in just about every theme for every occasion you can imagine. From what I've gathered there's two types:

Recordable: The card will have a few buttons inside where you can leave your own message, each button corresponds to a separate audio recording. These cards have a small microphone soldered to the board, along with a 'record' button, and a small speaker (ohms vary, usually between 8-16Ω). Powered by one 3V button cell battery.
Pre-recorded: This card will have only one pre-recorded message, with no microphone and no record button. The recording on these types of cards varies based on theme, I had one with a quote from 'The Office'. Because this card has is much simplier than the recordable types the 3V button cell battery is typically mounted directly on the board. Speaker is similar to recordable type, 8-16Ω.

Opening the card we can see the small board inside. If you look close, each board has several small surface mounted resistors, denoted R1 for resistor 1 and so on. Since these resistors are too small for resistor colour code identification they have their value printed numerically on the resistor. The last digit (typically 3rd) is the multiplier, in the example shown here 512 = 51 x 10^2 ohms = 5100 kilohms. You'll need potentiometers of around the same value shown on each resistor in order to control volume and distortion of your turntables.

Here are the specifications for this project:

turntable 1 (recordable greeting card)

3 recordable butons
background beat (when buttons not pressed)
potentiometer (volume)
push-button power switch

turntable 2 (pre-recorded greeting card)

momentary switch to activate audio recording
potentiometer (sound alteration)

Step 3: Potentiometers

Potentiometers:
The potentiometers used are determined by the resistor rating on your circuit board. I used two different boards from two differnt greeting cards. The pre-recorded card circuit board had only 4 resistors, and only two of them produced a result I was looking for (augmented audio). The 5k potentiometer shown here corresponds with the 512 surface mount resistor mentioned in Step 2.

Wiring a potentiometer is easy. With the potentiometer knob facing us with the posts on the bottom, we can number the posts (from left to right) as 1, 2 and 3. The leading side of the resistor can be wired to post 1 on the potentiometer, and post 2 and 3 can be wired together an attached to the trailing side of the resistor.
What is happening is that the current is now being directed to the potentiometer where it can receive human control before being outputted to the speakers.

Decks:
to simulate the decks (surface records rest on while being played), any circular object which is non-pliable will work. I used small furniture mover pucks found at the dollar store. The pucks came apart easily, were the right diameter and had a round opening the perfect size for my potentiometer knobs.
Place your decks on the lid of the hobby box, my decks were slightly larger than the top. With the deck placement aligned, mark the center points of both decks, then create an opening in the box at each center point.

With potentiometers wired and openings in the hobby box lid, the potentiometer knobs can be pushed through the lid openings. Secure the body of the potentiometer to the underside of the hobby box lid so they don't rotate when the knob is turned.

Step 4: Deck Buttons (operation Buttons)

These audio greeting cards operate by a small tab slider on the inside of the card that completes the circuit when opened. When taking the circuit assembly out of the card the slider location is revealed. I wanted these turntables to operate at the touch of a button, so a switch was added to the slider location on both cards.

Since I used two different types of greeting card circuit boards I chose to have them operate independently, with two different power buttons. The pre-recorded circuit board had only one sound byte, so a momentary switch was added to one of the decks. This momentary switch corresponds with the potentiometer for the pre-recorded card. Secure the switch to the underside of one of the deck with hot glue, the top of the button should be operable from the top of the deck.

The recordable greeting card had more buttons to utilize, so a push-button switch was used for primary power. When the card is powered a background music sample is played and the user can then press any of the recordable buttons at will to drop recordable sound bytes. This button was mounted on the lid between the two decks. Each of the recordable buttons were mounted to the underside of the other deck, again with the buttons operable from the top side of the deck.

Step 5: Speaker

To allow your sounds to be heard create openings in the hobby box. I was able to fit both speakers between the potentiometers to let the sounds transmit through small openings in the lid, located under the decks.

Create openings in the lid near each potentiometer knob to pass wires from the underside of the deck through to the circuit board.

Step 6: Sandwich Components

To reduce space requirements I sandwiched the circuit board to the back of the speaker. The second circuit board and battery cell were then sandwiched onto these. Hot glue tacking everything together.

Step 7: Prepare Base + Close Assembly

Since this project is so small the entire project can fit into a small hobby box, making it wearable.
The bottom portion will house the watch strap and provide space for the remainder of the components which will be fixed to the underside of the lid.
Create slit openings on the bottom of the hobby box which will accommodate the watch straps. Feed watch straps through openings and secure the watch body to the bottom of the hobby box.

Place lid with components on to base of hobby box, some components may need to be repositioned to allow the box to close. The box was then sealed using small gobs of hot glue. Place decks with buttons onto potentiometers and you're ready to start dispensing your DJ beats to your friends.

Step 8: Drop Beats

Circuit bending isn't always an exact science and working the potentiometers requires some patience, especially when distortion is desired. I was able to complete this project successfully and am still finding neat sounds to make on the greeting card circuit board by experimenting with different resistors and potentiometers.

Did you make your own version of this project? Post your results in the comments below.
Have fun! Happy making :)