Looking for the simplest, cheapest and most useful LED project? Look no further than the Squeeze Flashlight!

Supplies

5 mm LED bulb

CR2032 3V coin cell battery

8.5' x 4" block of craft foam

a few inches of electrical tape

Step 1: Prepare the LED

The LED bulb has 2 leads, an anode (+ lead) and a cathod (- lead). The annode is the shorter of the two leads, take it and bend it out an inch. Take the non-bent lead and tape it to the center of your craft foam as shown in the picture. Please note the anode has no tape on it.

Step 2: Add the Battery

Now take the CR2032 battery and place it on the cathode (+ side of the battery down) and secure it to the craft foam by taping it as shown in the picture. Please note that the anode is still tape free.

Step 3: Close It All Up

Now fold your craft foam edges to the center, overlapping the CR2032 coin cell as shown in the picture and secure with tape to close the package. That's it, to turn the flashlight on, simply squeeze the craft foam. The flashlight will turn off when pressure is released.

Ok, now some theory. How does it work? The LED is a simple semiconductor which will light up when approximately 2.1 volts at 20ma is applied between the anode and cathode. The coin cell is the perfect device to provide this voltage because it cannot provide enough current or voltage to damage the LED. Basically any 3 volt coin cell can be used. I selected the CR2032 because it is the most commonly used coin cell so it will be the cheapest one you can find. The LED was ordered in bulk from eBay. LEDs can also be harvested from dead toys or LED Christmas lights. Enjoy!