By Super Awesome Sylvia and her dad, James
Are you curious about experimenting with electronics, but the fear of electric shock or soldering iron burns keep you away?
Why not try squishy circuits! With a special recipe of food-safe, kitchen-made, pliable dough developed at the University of St. Thomas, kids of all ages can easily use their hands to mold their very own simple circuits right before their eyes! Lets go!
For this build, we’ll be mixing up two different types of dough, and then experimenting. For both types of dough, we’ll need:
- Deionized or distilled water (Tap water is OK if you don’t have any)
- Vegetable oil
- Cream of tartar (or lemon juice to substitute if you can’t find the stuff)
- Food coloring
- And last but not least, some measuring cups and a medium sized pot to mix it all up in
For basic experimentation, you’ll need:
- 6 volt battery pack (or 9 volt battery)
- Toy motor
- Or head over to the Maker Shed and get the Squishy Circuits kit, perfect for classrooms, it’s got everything you need to start experimenting with your conductive dough.
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First, lets make the conductive dough: Get out your medium sized pot and add in the following ingredients:
- 1/2 cup tap water
- 1/2 cup flour
- 2 tablespoons salt
- 1 ½ tablespoons Cream of tartar (or 4 ½ tablespoons lemon juice to substitute) ,
- ½ teaspoons of vegetable oil
- and last but not least, some food coloring!
Coloring the dough isn’t required, but it really helps ensure it doesn’t get confused with our insulator dough. Once that’s all in the pot, mix it right up.
Once mixed cold, put the pot on the stove over medium heat (adults should help!), constantly stirring. It won’t be long before it gets thicker and thicker (and much harder to stir), eventually turning into a big lumpy ball. Turn off the heat, and get yourself a big flat surface sprinkled with about 1/4 cup of flour, then empty out your big lumpy ball onto it. Start carefully rolling and kneading the dough around in the flour until it’s the right consistency (careful, it’s hot!). And that’s it, now you’ve got your very own conductive dough!
Now for the insulating dough: Get out a large bowl and pour in:
- 1/2 cup flour
- 1/4 cup sugar
- 1 1/2 tablespoons vegetable oil
Mix it all together, then pour in the distilled water 1 tablespoon at a time, mixing it in fully before adding another one. Keep adding until your mix looks sticky and doughey like the picture below, then take it out, and like before, roll it around on a flour coated surface until it’s the right consistency.
Now to experiment! But.. what is a circuit? and what is.. electricity?
Electricity is all around us, all because of Atoms and their charges. An atom is the simplest form of any element, and they’re super important. Atoms are made up of protons and neutrons in the nucleus, surrounded by whizzing whirring shells of negatively charged electrons. With most metals, like our friend copper (commonly used for wires), their outer electrons are loose and easily shared between each other, these “free” electrons make them great electrical conductors, passing a charge from one atom to the next.
With other elements, like old curmudgeon oxygen, they don’t like to share their electrons much, making them great electric insulators, keeping any charge from moving freely to other atoms very easily.
To make the passage of electrical charge do some work for us, we use a circuit. First, we need a battery. The electron charge wants to flow from the negative to the positive terminal, but the charge has no way to do it on its own through the air. Once we add long strings of conductive elements (wires, or our salty conductive dough), we can help them get there. Include a resistor and an LED, and our circuit is complete!
In every circuit, you have three basic things at play:
- Voltage (measured in volts), is like the pressure for the electrons to move out of the battery.
- Resistance (measured in ohms Ω) is whatever impedes (slows down) the flow of electricity through something, lowering the effective voltage.
- Current (measured in amps) is a measurement of the actual power moving through a circuit in a given time, to see it, you need both voltage and resistance in a complete circuit.
Their relationship in a circuit is called Ohms Law, something we’ll have to talk more about in another show.
Now to experiment!
First, a few rules: Never touch your batteries’ leads directly to each other, that would cause a short and could damage the battery. Also, never hook an LED directly up to the battery, it will go “pop” and never work again!
First try just rolling up two bits of dough and attaching the battery leads to them, then connect an LED, as long as the polarity is correct, you should get light! Try a buzzer and a motor too. Notice if the dough touches the other piece of dough, the light will go out (or at least get very dim). Electricity is “lazy,” and will always take the path of least resistance, if it can get where it wants to go without turning on the light or doing extra work, it will.
Now try making a big doughnut of conductive dough, then a smaller doughnut of insulating dough, then one center squidge of conductive dough in the middle. With your battery hooked up to the center and the outside, you can hook up your LEDs in a circle, or experiment with series vs parallel circuits.
Once you’ve got the hang of that, try using the conductive and the insulating dough as your own squishy potentiometer! Put a large resistor between analog 0 and ground on an Arduino, hook one side to 5 volts, and the other side to Analog pin 0 with our RIFF sketch, and try to make some squishy music! As the length of dough changes, so does the resistance.
For more awesome experiments to try out, check the awesome and comprehensive St. Thomas Squishy Circuits Building page.
When you’re done, clean off any contacts with warm water, and store your dough in air tight plastic baggies to keep for up to two weeks.
That’s all we’ve got for this episode, remember to have fun, never stop learning, and get out there and MAKE something!
Check out more episodes of Sylvia’s Mini Maker Show.