I’m normally not impressed by the free toy inside kid’s meals at fast food restaurants. However, the Avatar Jake Sully McDonald’s Happy Meal toy caught my attention due to how it lit up. And, as you'll soon see, breaking open the toy revealed some useful electronic components.
Jake Sully toy head lights up (artistic emphasis added).
After lunch, my son immediately lost interest in the toy. Perhaps if the arms and legs were hinged, it could have joined his action figure legion in participating in an imaginary battle. But, all it did was light up. (There’s a toy design theory that states the best toys are those that the child directs in new unplanned ways, rather than a few specific actions intended by the manufacturer.)
As my wife and I were cleaning up, I noticed that the Avatar toy flickered off and on, even though no one was playing with it. At first, I assumed it was programmed to flash randomly, but it turned off when we stopped moving. Next, I hypothesized that the illumination was based on sound or touch, yet neither set of my test inputs seemed to correlate with the flashing.
Finally, I recognized that the flashing corresponded with vibration. Having opened up a pair of blinky shoes, I guessed that the Happy Meal toy contained a spring and metal tube. The only way to know for sure is open-heart surgery!
Breaking open the toy would also satisfy my curiosity about the light source. Years ago, blue LEDs were expensive enough that toys would often contain a red, orange-yellow, or off-green LED. Even though the Jake Sully toy is made of translucent blue plastic, which might normally tint a blander color LED, I suspected that it contained a true blue LED.
Given that this was my kid’s toy, I would have preferred to find a non-destructive way to look inside. However, these toys are usually well sealed to avoid harming a small child; else they swallow a small electronic part.
Toy back with speaker, power switch, and triangle screw.
The back of the toy includes a speaker with air-holes, a slide-switch for power, and a triangle screw. The speaker is odd, because the toy we received doesn’t make any noise. Perhaps a bad unit? Or perhaps a clue?
Unscrew triangle screw with triangle screwdriver bit.
To open up the toy, I started with the most obvious -- unscrewing the triangle screw. For a number of years, I used the tip of a triangle file, but now I use a set of four triangle power bits. Specifically, Jake seems to take a TA23 0.090″ (McMaster-Carr #5941A13 $2.87)
Unfortunately, removing a single screw was not enough to remove the back of the toy. Something more drastic needed to occur.
Detach toy arm with pliers.
A pair of pliers with serrated teeth gripped the slightly squishy arms enough to remove them. With enough effort, I suppose the arms could be reinserted, but, realistically, I think we’re past the point of no return.
Crack toy chest open with pliers.
The shoulder socket hole provides an access point to begin prying and nibbling away at the toy’s chest plate. Rather than coming off in a single piece, the plastic tended to rip away a chunk at a time. Still, a big enough crack formed at the join line between the major molded pieces to make separation fairly easy.
The toy’s cavity is hollow and fairly spacious. There are a number of surprises inside.
Inside McDonald’s avatar toy.
A standalone motherboard holds all of the electronics. I can’t wait to see what is underneath the big blue object in the center. Surely it is a spring and metal contact for sensing vibration!
Beneath Jake Sully’s mask (under the face) is a solid clear piece of plastic where the LED is aimed.
Acrylic light pipe inside toy face.
The solid clear plastic piece is made of acrylic. It is shaped to distribute the blue LED light more evenly. This is called a “light pipe”, which is used to provide designer-styling in a wide range of electrical devices. This is a really nice touch, but almost seems unnecessary in a plastic container that I would have expected to have fairly good light diffusion by itself.
The large blue cover on top of the circuit board has a couple of tabs holding it in place. A small screwdriver can release the tabs to pop off the cover.
Three coin cells.
I’m shocked to find three discrete coin cells. Wow! It is very unusual to find a true battery holder in a disposable toy.
Each coin cell is a 1.5 volt alkaline. That makes 4.5 volts total (a battery of three cells in series), which is necessary to provide enough voltage to light a blue LED.
The coin cell is of type L736H of 0.31″ diameter by 0.14″ thickness. This type is compatible with SR41, LR41, 192, V3GA, LR736, L736, L736F, AG3, 192, LR41, G3, V36A, L736H, G3A, and GP192. A popular online retailer sells a pack of ten for $3.79 (38 cents each). That means the batteries alone are worth a dollar.
Avatar toy circuit board with blue LED, coin cells, and speaker.
With a little desoldering, you can get a piezo speaker and a blue LED from the motherboard as well.
Avatar circuit board.
The PCB (printed circuit board) has surprisingly few passive components. There’s a 30000 ohm surface-mount resistor (marked 303) and a 52 nF capacitor (inexact measurement). The black blob in the center is epoxy covering a custom integrated circuit.
Nowhere do I see a vibration sensor. Scratching my head, my best guess was that a crude motion sensor (accelerometer) is built into the chip that is covered by the black epoxy. But, I was wrong!
Several loyal readers (Frank and Tristan) suggested that the speaker is wired as a piezoelectric sensor. That is, rather than the microcontroller providing power to the speaker to produce vibrations as sound, sound (or contact) vibrates the speaker to produce power at the microcontroller input.
Indeed. Even the slightest contact with the “speaker” causes the LED to flash. When I shorted out the “speaker”, the device no longer responded to vibration. Neat trick.
Another unusual aspect of this toy is the silk screened text on the PCB. Marks include:
There seems to be two very different groups at work in this toy. The people that made the standard low-grade no-joint throwaway body. And the people that included three non-soldered coin cells, a wired speaker/sensor, acrylic light pipe face, blue LED, and a & microcontroller.
Let this be a lesson to you junkbot enthusiasts. Next time, rather than discarding your Happy Meal toy to the trash, take a moment to crack it open to see if you can salvage a couple of useful parts!