How to Make Easy and Extreme LED Throwies

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An LED throwie is a small glow-dot made from an LED, a coin-cell battery, tape and a disc magnet. Press the LED leads to the battery, wrap the connection tightly, add the magnet on the positive side, and it will cling to a ferromagnetic (iron-containing) surface.

What you need

• One coin-cell battery per throwie (the basic instructions do not specify a single cell model; the lantern variant uses a CR2032)
• One LED per throwie
• One small disc magnet per throwie
• About 7 inches of electrical or strapping tape

For an enclosed lantern, also gather a PVC pipe cap and plug, thread-sealing tape, a binder clip, a 10mm LED, a drill with a 3/8-inch bit, a drill vise, a hot-glue gun, pliers and wire cutters as needed.

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Make a basic LED throwie

1. Check polarity. Hold the LED’s longer lead (the anode) against the coin cell’s positive (+) face and the shorter lead (the cathode) against the negative (–) face. The LED should light.
2. Secure the circuit. Cut approximately 7 inches of tape. Wrap the LED leads tightly around the battery so pressure stays constant and the light does not flicker.
3. Add the magnet. Place the disc magnet on the battery’s positive side and continue wrapping the tape tightly around the assembly.
4. Prevent a short. Keep the cathode from touching the battery’s positive edge. That contact shorts the circuit.
5. Attach it. Place the finished throwie on a ferromagnetic surface. To remove it, slide the magnet sideways while lifting it with a fingernail or tool instead of pulling straight outward.

How long does an LED throwie last?

Make: estimated 15–30 minutes to build a throwie in its 2012 project, and its 2012/2015 page describes roughly 1–2 weeks of glow. That is an experience-based estimate, not a controlled battery-life test: weather and LED color affect the result.

Ways to make an “extreme” throwie

Sliding on/off switch

Sandwich the LED’s longer lead between cardstock tabs. A sliding tab then makes or breaks contact, giving you a simple manual switch without adding a separate component.

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• Overview: 5 mm Frosted Foggy Round Small Lens (Viewing Angle: 20 degrees) 2 leads, 5 colors x 20pcs = 100pcs Mixed Leddiode, 20 for Each Single Color (White Red Green Blue Yellow)
• White: 6000K-9000K(7000K 8000K) Red: 620nm-625nm Green: 515nm-520nm Blue: 455-465nm Yellow: 588-592nm(590nm 591nm)
• Shipping Weight: 0.04kg, (Pack of 100) (5 Colours, Each Color 20pcs / Through Hole DIP 2pins 5mmled LEDs Set)
• Compatible with: Indicator Lights, DIY PCB Circuit, Arduino, Raspberry Pi, hobby, Science Experiments, Colorful Throwies Project, Breadboard, T1 T-1 Bulb, Bulk 3.2v 3.3v Parts Replacement,Invisible Black Light
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Throwie bugs

Chain several throwies together for a larger pattern or insect-like form. Long chains may not hold to a metal surface as well as individual units because the combined weight and leverage reduce the grip at the attachment point.

Indestructible LED Lantern

Enclose a CR2032 and 10mm LED in a PVC cap-and-plug assembly, using thread-sealing tape and hot glue where appropriate. The Make: project reports that its lanterns survived a week submerged, freezing and laundering, and says they glow for days. Those are reported project results rather than a standardized durability rating.

LED Jellies

Shape the throwie into a glowing jellyfish form for a soft, suspended display. The adaptation changes the enclosure and appearance while retaining the LED-and-cell light source.

Floaties and Swimmies

Remove the magnet before placing a throwie in a helium balloon or a plastic fish toy. Without the magnet, the light can float or move with the toy instead of attaching to metal.

Programmable and motion-sensing versions

Add an ATtiny microcontroller to send Morse-code messages. A guitar-string intermittent switch can create a flickering, motion-sensitive effect. These versions require electronics assembly and programming beyond the taped basic build.

Choosing a variant

Practical checks and fixes

• LED stays dark: reverse the LED so the longer lead contacts + and the shorter lead contacts –.
• LED flickers: unwrap and retape the leads with firmer, even pressure.
• Battery gets shorted: move the cathode away from the positive rim before tightening the tape.
• Throwie will not stay attached: use a clean ferromagnetic surface, inspect the magnet and reduce the length or weight of any chain.
• Removal is difficult: slide the magnet sideways, then lift; do not pull straight away from the metal.

What makes the simple build useful

The basic throwie is fast, inexpensive and easy to multiply: Make: estimated 15–30 minutes for the project, and a 2012/2015 materials note listed 25 disc magnets for about $13 at the time. That price is historical, not a current quote. Start with the taped version, then choose an enclosure, switch or controller only when your display needs more weather resistance, control or movement.

Quick Recap

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100 pcs(5 colors x 20 pcs) 5mm LED Diode Lights Assortment Kit Pack (Diffused Round Lens DC 3V 20mA) Lighting Bulb Lamp Assorted Variety Color Electronics Components Light Emitting Diodes Parts

Forward Voltage: R/Y 2.0-2.2V; B/G/W 3.0-3.2V

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