Make: Projects

LED Throwies

Add color to any ferromagnetic surface in your neighborhood.

LED Throwies

Make and toss a bunch of these inexpensive little lights to add color to any ferromagnetic surface in your neighborhood.



Step #1: Test the LED.

LED Throwies
  • Pinch the LED’s leads to the battery terminals, with the longer lead (the anode) touching the positive terminal (+) of the battery, and the shorter lead (the cathode) touching negative (-).
  • Confirm that the LED lights up.
  • Tape the LED leads to the battery by cutting off a 7" piece of strapping tape and wrapping it once around both sides of the battery. Keep the tape very tight as you wrap. The LED should not flicker.
  • Place the magnet on the positive terminal of the battery, and continue to wrap the tape tightly until it’s all done. The magnet should hold firmly to the battery.
  • The battery’s positive contact surface extends around the sides of the battery. Don’t let the LED’s cathode touch the positive terminal, or you’ll short the circuit.
  • That’s it — you’re ready to throw (or make a few dozen more). Throw it up high and in quantity to impress your friends and city officials.

Step #2:

LED Throwies
  • A throwie will shine for about 1-2 weeks, depending on the weather and the LED color. To get one off a ferro-magnetic surface, don’t pull it, or it may come apart. Instead, apply a lateral force to the magnet base, and slide it off the surface while lifting it with a fingernail or tool.
  • Throwies naturally chain together in your pocket, making multi-segmented throwie bugs, which will also stick to metal surfaces if they aren’t too long.


This project originally appeared in MAKE Volume 6, page 116.