Facilitated bySharon CichelliPrincipal Technical LeadHeadspring in Austin, TexasWith thanks to Squishy Circuits University of St. Thomas http://www.stthomas.edu/squishycircuits/CircuitsIn Play Dough
Try this!If the blobs touch, the LED wont work.
Building a CircuitA circuit is an unbroken loop for electricity to flow through.Use the dough to connect each LED leg to a battery terminal. But dont let the two clumps of dough touch each other. Thats a short circuit.Not lighting? Flip the orientation of the LED.Nothing special about the dough; salt water conducts electricity. (See recipe next.)
Mix: cup water tablespoon vegetable oilfood coloringStir that into:1 cup flour cup saltMix it, then knead it with extra flour until it is the consistency of fun.Conductive Play Dough
Thats tin foil, not dough.
Motors and Buzzers9 volts is too much for these motors. They shut down to protect themselves.Each AAA battery is 1.5 volts, so two together gives 3 voltsjust right.Use foil instead of dough. The dough has a high resistance, so it starves the motor of enough current. The foil is more conductive. The buzzer motor is like the one in your phone.
Watch out for short circuits
Battery terminals connected directly to each other get hot!An LED connected directly to the battery ruins the LED.
Short CircuitsA short circuit happenswhen current flows through a different path than the one you wanted.In the LED + dough circuit, if the dough blobs touch, current will go there instead of through your LED. So the LED doesnt light.Foil has much less resistance than dough; foil lets more current through. LED + foil, the LED gets more current than it can handle. Permanently.
Did you fritz an LED during the workshop? Dont sweat it; they cost pennies. Now were learning about current!
Keep making circuits!The recipe is a few slides earlier.Batteries, battery holders, LEDs, motors, speakers, sensors can be found on Amazon, eBay, Adafruit.com, Sparkfun.com, and at Frys and Radio Shack. (Shush. I miss the Shack.)These LEDs are through-hole (not itty bitty surface mount), 10mm diameter (5mm is fine), and have a forward voltage (minimum volts to work) of about 2.7 volts.
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