Instructables

Indestructable LED lanterns

Picture of Indestructable LED lanterns
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After seeing the article "the eternal flame" in MAKE: Magazine, my first thought upos seeing the project was that it's not really "eternal" because you can't change the battery if it's glued shut!  After reading, I saw that it used teflon tape to make it watertight and re-openable, but not before a project idea came about. 

Several days later, I completed my new wirelessly charged, rechargable indestructable LED lantern.   While it's not nearly as cheap or easy as the version in make, this one can stand some pretty tough abuse, as well as costing less after a few uses, depending on where you buy batteries. Don't forget to vote for me in the lamps and lighting and UP! Contests. If I win the UP! I will update with an even tougher 3d printed lamp, and more tests. 

For a video and alternative guide, go to http://www.designnews.com/author.asp?section_id=1362&doc_id=245321  where this project is also published, along with a video. 
 
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Step 1: Materials

Picture of Materials
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To make this you will need:
1- rechargable AA battery (per lantern)
1-1k resistor (per lantern)
1-High-power white LED (per lantern)
3-other-colored low power LED (3 per lantern)
1-AA battery case (per lantern)
1-4401 transistor (per lantern)
1-low inductance, center-tapped inductor (per lantern), (watch a youtube video on a "joule theif, this uses a similar circuit)
OR
1-3.6V rechargable battery
1-low-power LED
1-High-power white LED
The first option usually lasts much longer or is cheaper (depending on the battery).  But, it is more complex.  Both options need:
2-1” PVC slip cap
1-1” diameter pipe, 3” long (cut from longer piece)

Charger circuit:
1-555
1 -470 ohm resistor
1-0.01uf capacitor
~20 x 2n3906 transistors (exact number depends on primary coil) (Jameco.com, part# 38375)
15 x feet magnet wire (7.5 or so per lantern)
1 x 12V power supply
Do you have a switch on it? How do you turn it on and off?
jduffy54 (author)  basementhacker1 year ago
It actually doesn't have a switch, but it doesn't really need one. The battery last several days, and the main light turns off while it's charging (thats what the far-right indicator LED is for, the one connected to the mylar capacitor). This brings the transistor base low, and turns off the circuit for charging,
DIY-Guy1 year ago
"What other crazy electronics-tortures should be attempted?"
Microwave it if you dare!
jduffy54 (author)  DIY-Guy1 year ago
I would, but the only microwave I would be able to use is my parents, and I doubt they need melted PVC and battery acid in their microwave.
Would the water proof glue support a direct impact of the light? Would the glass of the LED take any abuse? Impressive wireless charging though.
jduffy54 (author)  IR0NxLEGEND1 year ago
If by direct impact you mean throwing it at a wall led first, probably not without epoxy. With enough epoxy on the inside to cover past the bottom of the led, it's virtually unbreakable. The led dome does scratch, but that doesn't do much to the light itself. It's not actually glass, it's a clear resin, or plastic.
And thanks, but it's really not all my idea, it was just inspired from RFID, but without the communication, and with a lot more power.
How does the wireless charging work?
jduffy54 (author)  basementhacker1 year ago
I'll edit the explanation into the guide, but until I do, I'll leave an explanation here.

The sender circuit rapidly changes the power going to the coil, pulsing it thousands of times a second. This causes a strong, varying magnetic field to surround the coil, which also rapidly pulses. When the receiver enters this magnetic field, it pulls on the electrons in the coil, causing them to move into the rest of the circuit. (A permanent magnet will not do this unless physically moved about the coil, which is how generators make power.

Once the electrons are moving, current is flowing through the circuit, and once it is limited to a single direction and evened out with a capacitor, it charges the battery and powers the lights. This basic principle is actually how almost all wireless transfers work (though most use a single wire instead of a coil). The coil method is most commonly used in from-ac power supplies, which use two coils and a magnetic medium between the two to increase the efficiency of the transfer.
so just like transformer but without core?
jduffy54 (author)  tutdude981 year ago
Precisely, but this is at a much higher frequency than the normal 60hz
Awesome! Thanks!
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