Hack Your Toy

Introduction

You’ve learned how to turn different things on and off with varying methods - magnets, touching, and tilting. Things you’ve turned on so far have been parts of your Maker Kit, such as LEDs and motors. But what if you wanted to turn on some external device, such as an electronic toy? In this project, we’ll do just that!

Electronic devices usually have their own power supply, e.g., a battery. That’s why we’ll sort of divide the circuit in two. Arduino will use its power supply, and the toy its own. You’ll need a transistor for that.

For this exercise, you’ll need an electronic toy. The toy has to work, and you must be able to take it apart so that you can get your hands on the two wires (ground and voltage wires) coming from its power supply. Below is a video of the Mehackit Dino, which is turned on with the help of a microphone by clapping your hands! What kind of mechanism would you like to use to turn your toy on?

Toy hacking - Dino

Parts

In addition to Arduino, the USB cable, breadboard, and wires, you’ll need:

Part	Image	Description
NPN transistor		You have three of these in your Maker Kit. Make sure that the component has MP5 written on it, not TMP (like in the temperature sensor) or FT66T (like in the melody generator).
Diode		In this exercise, the diode is used to make sure that possible surges don't move from the toy's power supply to Arduino. The diode allows current to flow toward the striped end, but not the other way
An electronic toy to hack		The toy must work and be relatively easy to take apart so that you can find the two wires going into the power supply.
Wire cutters		For cutting and peeling the toy's wires.
Soldering iron		This is not essential, but it will make your job easier! Ask your instructor if they could arrange you one for some of the classes.
Screwdriver		For taking the toy apart. You can find a small Phillips screwdriver with a black handle in your Maker Kit. If there are other screws in the toy, ask your instructor for help!
Resistor 1 kΩ		The resistor resists the flow of electric current. The value of the resistor is measured in ohms (Ω) and announced in the component in stripes of different colors (in this case brown, black, red and gold)
Reed switch		Closes the circuit when a magnet is brought close to it
Resistor 330 Ω
LED		The longer leg (the one with the bend in the picture), i.e., anode to the + -terminal, i.e., to Arduino's pin. The shorter leg, i.e., cathode to minus-terminal, i.e., ground.

Circuit

The first aim is to turn on the LED with a transistor. Later, we’ll replace the LED with an electronic toy, which you can turn on with the same logic.

Note, that the LED isn’t connected to Arduino’s digital pin, so you can’t directly use it through Arduino! This time, you’ll control the LED through the transistor.

• Connect the longer leg of the LED through a 330-ohm resistor to Arduino’s 5V voltage and the shorter leg to the transistor’s leg that is on the right side.
• Connect the middle leg of the transistor through a 1000-ohm resistor to pin 6.
• Connect the left leg of the transistor to ground.

The Aim of the Program

When the switch is closed, the middle leg of the transistor receives voltage from pin 6. Now, the transistor connects the other two legs and the LED’s (and later the toy’s) circuit closes. When the switch is not closed, the transistor receives no voltage, the LED’s circuit disconnects and the LED isn’t on.

Necessary Commands

• pinMode(port, setting)
• digitalWrite(port, value)
• digitalRead(port)
• delay(time)

Programming 1/2 - Testing with the LED

The aim is to first try if you can use the LED through the transistor. Later, we’ll replace the LED with the electronic toy!

void setup() {
  pinMode(6, OUTPUT);
}

void loop() {
  digitalWrite(6, HIGH);
  delay(4000);
  digitalWrite(6, LOW);
  delay(4000);
}

Finding the Toy’s Power Supply

With the instructions above, you turned the LED on and off by using Arduino. Next, you’ll turn on the toy instead of the LED. The legs of the LED are simply replaced by the two wires of the toy!

1. Make sure your toy works! If the toy is old, the batteries may have run out. In that case, change the batteries and check again. When you’re done, remove the batteries.
2. You should get your hands on the two wires coming from the toy’s power supply running inside the toy. The power supply is often under or at the back of the toy, which is why you’ll need to take the toy apart a bit reach them. Start the disassembly by removing the outer casing of the toy (this may require some unscrewing). This way you’ll get a look inside the toy.
3. Open the other screws as much as you need to find the wires going to the toy’s power supply. If you’re hacking a plush toy, you may need to pull out the toy’s stuffing to find the wires.
4. Use the wire cutters to cut the grounding wire (it’s often black) approximately in half.
5. Put the batteries back in. The toy won’t start because the circuit is not closed. Connect the ends of the grounding wire. The toy should start.
6. Now you can move to the next tab, where we’ll replace the LED with the toy!

Connecting the Toy

Just like before, applying voltage to the middle leg of the transistor connects the other two legs. Connect the two ends of the grounding wire you cut to the left and right leg of the transistor.

• Connect the reed switch to pin 5 and to ground.
• Connect the middle leg of the transistor through a 1000-ohm resistor to pin 6.
• Connect the grounding wire of the toy’s power supply to the left leg of the transistor. Connect this leg to Arduino’s ground as well.
• Connect the grounding wire going to the toy to the right leg of the transistor. Also, connect the right leg through the diode to Arduino’s ground. Make sure that the stripe in the transistor is pointing towards the transistor! That way, current flows to the transistor, but not the other way round.

Programming 2/2 - Controlling the Toy

void setup() {
 //Set the state of the reed switch to INPUT_PULLUP
 //Set the pin of the transistor to  OUTPUT
}

void loop() {
  //If the reed switch closes, apply voltage to the transistor and start the toy
}

Further Development

When you’re able to start the toy with the transistor, you can develop your project further in many ways. Here are two options!

Testing different switches and building chain reactions

Previously, you turned on the toy with a magnet using a reed switch. How else could you start the toy? Could a magnet tied to a string swing next to the reed switch, which starts the toy, which topples a glass of water, which closes the next switch and starts something else… Use your imagination!

Circuit bending

Circuit bending means modifying the toy’s circuit. So far the only alteration you’ve made was cutting one wire. You could, for example, modify the toy’s sounds by adding a variable resistor in a convenient place in the circuit. Below is a video introducing you to the world of circuit bending!

chewy01234: Basic circuit bending tutorial