What You’ll Need



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• Water
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• Flour
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• Salt
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• Cream of Tartar
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• Vegetable Oil
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• Sugar
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• Alum
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• Distilled Water
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• Food Coloring
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• LEDs
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• A DC power supply, like four AA or AAA batteries encased in a pack with added terminals
• 



Making the Dough

You didn’t think we were using regular old store-bought Play-Doh did you? We’ve got to mix our own dough, and we need two kinds: conductive and insulating. Distilled water and sugar keep the insulating dough’s resistivity high, preventing electrons from flowing through, while salt and cream of tartar keep the conductive dough... well, electrically conductive. While you’re mixing, add food coloring to each batch so you can tell the difference between the two.

 
Insulating Dough

To make the insulating dough, mix 1 ½ cups of flour, ½ cup of sugar, 3 tbsp. of vegetable oil, ½ cup of distilled water, and 1 tsp alum (as a preservative) in a medium size pot or bowl. Stir it until it until it starts getting a doughy consistency, adding a little distilled water if your mixture is too dry, or extra flour if it’s too moist. Coat a flat surface with some flour and knead your dough into a ball.

 
Conductive Dough

For the conductive dough, mix 1 ½ cups of flour, ¼ cup salt, 1 tbsp of vegetable oil, 1 cup of water (tap is fine), and 3 tbsp cream of tartar, in a medium size pot. Heat it over medium heat, stirring constantly. It will start to dry out and thicken into a mound of dough as you continue to stir. Carefully remove the dough (it’s hot!) onto a flat, floured surface, rolling it out so it can cool faster. Once it’s cooled, you can knead it into a ball.
Basic LED Circuit

Now comes the fun part. Pinch off two pieces of conductive dough, rolling each into a ball. Pinch off one piece of insulating dough and roll it into a ball, then sandwich it between the two conductive pieces. Plug the power supply terminals into each conductive piece, with an LED connecting the two. Switch on the power supply to see the LED light up.
NOTE: The conductive dough is resistive enough that you shouldn’t need to add resistors to your circuits to reduce the voltage across the LED.
Parallel Circuit


In a parallel circuit, the current is split among multiple paths, rather than a single path. You can use the same setup from our Basic LED Circuit, but now stick multiple LEDs across the insulating dough. They should all light up, but as you add more, you may notice they all shine equally dimmer as less electrical current flows through the LEDs.
Series Circuit


A series circuit will end up looking a bit like a caterpillar, with alternating pieces of conductive and insulating dough chained together, capped on either end with a conductive piece. Chain multiple LEDs through the conductive dough, and you’ll notice the ones at the end are far dimmer than the first few. That’s because less current is making its way down the series; the current only has one path, and that’s through each LED.
More Ideas and Hints

Make sure, when you’re wiring up your circuits, that the long end of the LED is directed towards the positive side of the power supply. You’ll also want to wipe off your components and ledes when you’re done — since the conductive dough is salt based, it’s corrosive.

Tired of LEDs? Trying hooking up a motor, a buzzer, or any other electrical component you’d like with your playdough. Just be sure your power supply has enough voltage to juice it!
Original article by Christina Bonnington. Video and photos by Michael Lennon.