Click on this link to see the LED Throwies in action in NYC thanks to resitor and fi5e!
Step 1: Materials List
Part: 10mm Diffused LED
Vendor: HB Electronic Components
Average cost: $0.20 avg per LED
Notes: Cost reductions for larger quantities. Comes in red, blue, amber, white in both diffused and clear. Diffused works better than water clear for the Throwie application. HB has even created a Throwies packs page with deals on 10mm LEDs and lithium batteries!
Part: CR2032 3V Lithium Batteries
Cost: $0.25 per battery
Notes: Cost reductions for larger quantities. With the 2032 Lithium batter, depending on the weather and the LED color, your Throwie should last around 1 -2 weeks.
Part: 1-inch wide Strapping Tape
Vendor: Your local hardware store
Cost: $2.00 for one roll
Notes: One roll will make many throwies
Part: 1/2" Dia x 1/8" Thick NdFeB Disc Magnet, Ni-Cu-Ni plated
Cost: $13.00 per 25 magnets
Notes: Cost reductions for larger quantities
Part: Conductive Epoxy
Vendor: Newark In One
Notes: The epoxy is optional.
Step 2: Test the LED
Note that the positive terminal on the battery has a larger contact surface than the negative terminal. The positive terminal extends around the sides of the battery. Don't let the cathode lead of the LED accidentally touch the positive terminal of the battery. This will create a short and cause the LED to function improperly.
For more information on LEDs click here.
For more information on batteries click here.
Step 3: Tape the LED to the Battery
The LED should not be flickering.
Step 4: Tape the Magnet to the Battery
If the magnet is stuck to a ferromagnetic surface, dont pull on the LED throwie. Apply a lateral force to the magnet and slide it off the surface while lifting it with a fingernail or tool.
Remember to keep the magnet away from conventional hardrives, credit cards and other data storage devices.
Step 5: Toss Your Throwie
Step 6: Plan a Campaign
Click on this link to see the LED Throwies in action!
Step 7: Other Applications and Upgrades
Other than tossing it, you can also use your LED throwie to write in the air with light while taking a long exposure flick. You can put them on your bike as an additional reflector. You can put the on surveillance cameras to make them more visible at night. You can use them to play a version of bocci ball on a magnetic surface in the dark.
You can make a better LED throwie by using shrink tubing on each lead to make sure they don't short to each other or the battery. This upgrade will allow you to bend the LED so it faces in the direction you choose. You can also dip the throwie in epoxy, silicon or potting compound to make an all-weather LED Throwie. A resistor in series would allow you to increase the throwie shelf-life. Bigger batteries = longer life. Stronger magnets = increased stick probability. You could add a solar panel, photocell, etc...Have fun.
Flickr instructional set for thowie on/off switch mod -- by A. Joyce, aka. EverythingDigital