My friend had a baby around the same time as me so I decided to prank him. I bought the same Elmo toy they had and took it apart. I added my own WiFi chip so I could control it over the internet. Now I can make the new “WiFi-enabled, IoT” elmo talk when ever I want, remotely!
First I added some tiny wires to each side of the button pad. This one had to be directly on the pad because the other end of the trace was under the potted chip. The other side of the switch was ground so we could pull that from the black wire on top of the board.
I made a small board with the Proton wifi chip from: particle.io. Then I used an optocoupler to simulate the button press. Because this switch is a “pull to ground” switch and I am already using a shared ground (because I power the Proton with the same batteries) I could have use a transistor, but I had these laying around. The optocoupler is super simple. When one side gets power and ground the other side completes a circuit, or in this case “pushes” the button. I connected to D0, and set it to digital write. Now from the particle API I can bring that pin “HIGH”, trigger optocoupler, which will simulate the button press.
I drilled a small hole in the case. I made the wires come out of the front so that they would be hidden if you opened up the toy to change the batteries. I wrapped the PCB in cardboard and tape and tucked it back in to elmo.
I gave elmo web interface that uses the particle.io API https://maustin.net/hax/elmo/. Now I have a mobile remote control.
Step 5 The Swap!
My friends are hosting the Super Bowl party this year. This will be the perfect opportunity to swap them out. I will pre-connect elmo to the their wifi from outside, then we wait…