LED Throwies

by Q-Branch

10.9M3.8K1.5K

Intro: LED Throwies

Developed by the Graffiti Research Lab a division of the Eyebeam R&D OpenLab, LED Throwies are an inexpensive way to add color to any ferromagnetic surface in your neighborhood. A Throwie consists of a lithium battery, a 10mm diffused LED and a rare-earth magnet taped together. Throw it up high and in quantity to impress your friends and city officials.

Click on this link to see the LED Throwies in action in NYC thanks to resitor and fi5e!

STEP 1: Materials List

LED throwies consist of only a few inexpensive parts and can be made for ~$1.00 per Throwie. You can reference the parts list below or download the attached spreadsheet for more info on parts, part's numbers, vendors and application notes.

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
Vendor: CheapBatteries.com
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
Vendor:Amazing Magnets
Cost: $13.00 per 25 magnets
Notes: Cost reductions for larger quantities

Part: Conductive Epoxy
Vendor: Newark In One
Cost: $32.00
Notes: The epoxy is optional.

STEP 2: Test the LED

Test your LED to determine color, brightness and functionality. Pinch the LED legs, or leads, to the battery terminals. The longer LED lead, called the anode, should be touching the positive terminal (+) of the battery and the shorter LED lead, called the cathode, should be touching the negative terminal (-) of the battery.

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

Cut off a piece of 1-inch wide strapping tape approximately 7-inches long. Tape the LED leads to the battery by wrapping tape 2-3 times around both sides of the battery. Keep the tape very tight as you wrap.

The LED should not be flickering.

STEP 4: Tape the Magnet to the Battery

Now, place the magnet on the positive terminal of the battery and continue to tightly wrap the tape. The magnet should be held firmly 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

The LED throwie is ready to be tossed onto a ferromagnetic surface. Practice tossing your throwies. Work on your accuracy and your own personal technique. Every throwie wont stick every time, but if you toss them gently, they will stick eventually. Get them up high and in large quantities for greatest enjoyment.

STEP 6: Plan a Campaign

Now, find a building or structure that will attract the magnets, form a crew, wait until night, and get some throwies up. If you do it around a crowd of people, they will probably try to get into the act. It can quickly dissend into chaotic fun. Give a hand-full of throwies to a stranger and let them get up too. Remember, Throwies are only a temporary alteration of your local environment. Depending on the color, Throwies can last upto two weeks, but you arent going to cause any permanent damage, so most property owners wont mind. And The NYPD loves throwies!

Click on this link to see the LED Throwies in action!

STEP 7: Other Applications and Upgrades

Other applications:

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.

Upgrades:

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.

User Upgrades:

Flickr instructional set for thowie on/off switch mod -- by A. Joyce, aka. EverythingDigital

1425 Comments

everythingdigital 18 years ago

I have posted a how-to on making throwies with removable tabs where you can pull it out to turn the LED on and slide it back in to turn it bad off. It's not very hard to implement, and is quite useful for conserving battery power.

Here's the link: http://flickr.com/photos/everythingdigital/sets/72057594069888500/

I'm also working on throwies that automatically turn on upon sticking to something and off when they are removed (as suggested above), and I have a few prototypes working but there are still some bugs to work out.

Q-Branch 18 years ago

I have included your how-to on the G.R.L. Throwies site and in the upgrade section of the throwies instructables post. Thanks so much for the mods and looking forward to the next rev!

JulieHenriksen 9 years ago

Best quote: "Throw it up high and in quantity to impress your friends and city officials."

How long do they last?

njreyn 9 years ago

Unknowable. Friends can be fickle, and city officials often disappear once installed.

jamesbrosuk 9 years ago

not sure city officials would be that impressed.

BastidgeC 6 years ago

Throwing hazardous batteries around shouldn't be promoted. This instructable is awful.

Peregrine05 5 years ago

I made it and threw them on concrete. There was nothing exploding.

BastidgeC 5 years ago

The a*holes above throw these things onto buildings and the battery chemicals leach out in to the environment.

Mad4400 2 years ago

What do you think happens when they are disposed of in with general waste?

Peregrine05 5 years ago

I guess if the batteries die, they will leak waste materials. And that wouldn't be good.

devicemodder 2 years ago

I have made a throwie 3 months ago... still glowing on the same cr2032

VegaNadir 8 years ago

I appreciate the very informative article.

I have several 3mm LEDs that would work with the 3V CR2032 batteries. However, I know of some smaller 3V lithium cell batteries and would rather use the tiniest ones possible. I'm going to use them for something I've been working on and want the battery to be as invisible as possible.

If you please, what is the smallest sized battery you know of that would work for these? Also, I wouldn't mind if they were a little dimmer, so ought I to use less than 3V? Thank you very much.

davecolmenero 3 years ago

Try a resistor between battery + and lead. 4.7k should reduce current drain. Experiment with different sizes as light output will diminish with increased resistance.

jeff.verive 4 years ago

The smaller batteries contain less energy, so they won't last as long. However they might be a better option for red LEDs whose lower forward voltage can result in destructive current from larger cells. Smaller cells have higher internal resistance, and this serve to reduce the current to less-destructive levels.

Peregrine05 5 years ago

Very small batteries wouldn't last long.

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