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Cheap R2 Sound Generator

This Suggestion comes from Steven Otte

Steven is a is a professional newspaper editor from Florida. He is also as a steam-era model railroader, and a member of the moderating team of SimWatch, a 2-year-old Yahoo group for players of the computer game The Sims

The following his tutorials on creating a sound voice box for R2 from a 3 ½ figure.

 

The Idea:

Mattel's 3-1/2" AOTC R2D2 figure plays a variety of typical R2 noises when a panel on his front is pressed. It has a "vocabulary" of 8-10 distinct sounds ("words") which, when the button is pressed, the toy strings together in a random order, producing a wide variety of different-sounding "sentences." Attaching the sound chip in this toy to a set of battery-powered amplified speakers, like one would plug into a Walkman or a computer, would make these sounds loud enough to use as a sound generator inside a full-sized R2. (see pictures of finished product at the end of the tutorial.)

 

Parts Needed:

 

Tools Needed:

 

Step 1:

Usually, these speakers will come in a set of two. One will have a place to insert batteries, a power button, a volume control, and an audio cable that plugs into the mini-stereo or computer. Some models also have a bass adjustment knob. We'll call this one the "main" speaker. The other "satellite" speaker usually has only a cord, which plugs into a jack in the back of the main speaker. Set the satellite speaker aside for now.

Cut the stereo mini-plug from the audio cable attached to the main speaker, leaving about 5cm of wire attached to the plug, and set the plug aside for possible use in some future project. Returning to the cable attached to the main speaker, remove about 2cm of the outer insulation from the end of this cord and SAVE THIS INSULATION. Inside are three conductors. One will be the right-channel positive, one the left-channel positive, and the third is the common negative (ground).

Remove about 5mm of the insulation from the ends of each of these conductors.

 

Step 2:

Pull the rubber legs off the R2 figure. (They don't actually hold the halves of the figure together or anything, so if you like, use the hobby knife to cut them off at the top of the shoulder.) Then, grip the dome of the R2 figure in the pliers so that the seam of the two halves runs straight across (in other words, hold it so you are squeezing both ends of the seam, not squeezing the two halves together).

Then, using firm but careful pressure, squeeze just until you crack the glue seam. Do the same with the bottom of the body. AVOID squeezing the middle of the body, which encloses the delicate circuit board. Once both ends are cracked, slip a hobby knife into the seams and carefully separate the halves of the main body, being careful the knife blade does not stick far enough inside to cut any wires. Remove the top half of the body, being careful to watch where the front panel "vent" button goes when it flies off, which it will.

 

Step 3:

Inside, you'll see a small circuit board with a black dot in the middle (that's where the sound chip is) and a rubbery button below the dot. If  you're worried the button could fall off and get lost in the handling of the unit, you can pull it off the circuit board and set it aside until it's time to test the unit. Inside the figure's dome are a yellow LED and a small black speaker, which is attached to the circuit board by red and black wires. Touch a hot soldering iron to the contacts on the speaker to pull it free of the wires; those wires are short enough already, and you don't need to lose any more length by cutting them off.

Discard the micro-speaker or save it for another project. (You can see this speaker above the R2 in the assembly photo below.) The black wire is the ground; the red one is the positive.

 

Step 4:

Load the batteries in your stereo speakers, hook up the satellite speaker, and turn on the power. Use your alligator clips, tweezers or fingers to hold two speaker wires at a time to the red and black wires in the R2 unit and press the activation button to make R2 make sounds. If the yellow LED blinks, R2 is making sounds, whether you can hear them or not. Keep switching the wires around and testing the sound until you can figure out which wires in the speaker are which. In mine, the black was the ground, and the red and white were the left and right channel positive wires. I imagine this is a fairly common color scheme. But if your speaker has only two insulated wires inside its cord and the third wire is uninsulated, it's likely the uninsulated one is the ground.

 

Step 5:

Tie a knot in the speaker cord just above where the insulation starts. This is for strain relief.

 

Step 6:

See the photo below for reference. Twist the uninsulated ends of the two + wires from the speaker cable together and hold them in place with an alligator clip so you can "tin" the wires. This means using a soldering iron to melt a small amount of solder on the ends of the wires, so you don't have to apply solder while actually attaching the wires. Then tin the speaker's ground wire. Then, twist the speaker + wires and the R2's red wire together, secure them with an alligator clip and touch them with the soldering iron; since all three are already tinned, they should join together without applying more solder. Then do the same with the speaker ground and the black R2 wire. Push the button for one more test.

 

Step 7: Assuming the unit still works, cut the insulation you saved from Step 1 in half and push a piece on each of the soldered-together ends of the wires to prevent shorting (this job is much too small for wire nuts or electrician's tape). Pack one of the splices into the bottom of the dome, feed the cord through the notch at the top of the dome so the knot is inside, and push the other splice on top of it. (This way, the knot is in between the two splices, just in case the insulation works its way loose later on.) Replace the buttons and the top half of the body. Only the cord should emerge from the top of the dome; the knot inside will keep the cord from being accidentally pulled loose. Use rubber bands to hold the body halves together if they don't stay that way themselves.

 

Activation Options:

There are a few ways you could approach installing this into your full-size R2. The simpler way would be to use a radio-controlled servo to mechanically push the button when you wanted the sound activated.  (Since the figure's shell is styrene, you could easily use structural styrene shapes available at any hobby store to make a bracket to hold this servo in position.)

 

The more elegant, but more difficult, solution is to replace the activation button with an R/C switch. The figure's activation button is a simple rubber cap containing a carbon conductor which, when pushed onto the circuit board, bridges two contacts. If you use very fine, solid-core wire (like telephone wire), have a very steady hand, and tin the wire ends first rather than risking globs of solder on your circuit board, you could probably attach leads to these contacts, allowing you to wire in the R/C switch of your choice.

 

If you're thinking of permanently bridging the activation contacts with a drop of solder and wiring a switch into the battery contacts found behind the screw-attached door in the back of the figure instead, forget it. Activating the sounds requires only an intermittent contact; holding the button down (the same as soldering the  contacts together) does not produce continuous sounds. Another sound requires another contact. You'd end up with an R2 that would beep once, and never again.

 

Options:

Attaching the R2 unit's wires to a modular speaker jack (available from Radio Shack, part No. 274-249, $1.99 for 2) rather than hard-wiring it into the speaker would allow you to plug R2 into whatever sound system you wanted later on, and remove the need for mangling the speaker wires. Just remember that since the jack is stereo and R2 is mono, you'll have to bridge the + contacts inside the jack to make sound come out of both speakers.

The sound chip inside the R2 also activates an LED that blinks along with the sounds. You could remove this LED and extend the wires to automate some other action to synchronize with the sounds, such as changing a status display on the dome.

Pictures:

You can see the original button speaker at the top of the first picture.

 

 

Steven Otte

flagator@gate.net

 

 

 

FOLLOWUP

Thanks for telling us about wiring your speakers into the R2 figure. When I saw the amount of space in the head I realized that it would be easy to install an 1/8 inch phono jack in the head. This allows the figure to be connected to speakers easily with a common headphone cable so that I don't have to dedicate a set of speakers to the sound device.

I used pretty much the same method to open the figure but I drilled the hole out to accommodate a jack I bought at Radio Shack (Part Number 274-249, $1.99 for 2). After removed the speaker I used an Exacto knife to cut away much of the plastic that was used to hold the speaker in place because the housing for the jack is slightly larger and rectangular. I also removed a little of the plastic at the top of the head to allow the nut that comes with the jack to be screwed onto the top. I soldered the black wire to the common lead on the jack and bent it against the body so it would fit into R2. Then I bent both of the red leads towards the center and soldered them together with the red lead so that the sounds would play on both channels. Then I simply reassembled the figure and tightened the nut on the jack.

I hope this is useful,
Barry