"Dead" Battery Lamp




When batteries don't give enough juice to gadgets, you think that they are completely dead. But, all of them still have plenty of volts, and with a simple circuit you can unlock all of that power. This instructable makes an LED lamp which will suck all of the juice out of those batteries. If i had rechargeable batteries, such as sanyo's eneloop, I would never need to do this.

This is whats called a "joule thief" and it is an adaptation of those.

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Step 1: Parts

You will need:
1 3904 transistor
Some 3 volt Super-bright LED's
1 1000 ohm Resistor
1 Ferrite Torroid
2 Different Colors Of Wire
1 AA Battery Holder
Shrink Wrap Tubing
8 in. of Heavy gauge wire
Altoids Tin
Cheap Wire
Soldering Iron & Solder
Wire Strippers and Cutters

Step 2: Wiring the Toroid

Take 2 same lengths of wire and fold them over together to find a center point. Put the wire through the toroid and start winding equally until you have a whole layer surrounded by the wire which should be around 10 winds. Now take 2 of the different colored wires, and cut them shorter so they're not so long. Strip them, twist them together and solder them.

Step 3: Solder It

First, strip and twist 2 of the opposite colored wires together. Slip some shrink wrap onto the positive battery holder wire, and then twist the positive wire onto the other 2 wires. Solder those wires, and then shrink wrap them. Take another wire (the green wire for me) and strip it. Solder the wire onto the resistor, and shrink wrap it. Then, fold the transistor wire back, and solder the resistor to it. Take the last unsoldered wire from the coil (my red wire, not from the battery holder) and solder it to the right pin of the transistor. You should bend the pin out a bit so it doesn't short out. For the last pin, solder the ground wire (black) from the battery holder to the left pin. For the 2nd to last soldering step, measure 2 wires approx. 3 in. longer than your heavy gauge wire. Strip the ends of both, and solder 1 to the left transistor pin (the one with my black ground wire from my battery holder) and the other one to the right transistor pin (the one with my red coil wire). My red wire is + for the LED's and the black wire is ground for the LED's.

Step 4: Constructing the Lamp

Take the altoids tin, and mark out where you want the "stem" to be. Then poke some slits to allow for the heavy gauge wire and 2 wires to go through. Place the circuit in the tin and make sure it fits. Put the heavy gauge wire through the whole, along with the other 2 wires form the circuit. My heavy gauge wire had 3 internal strands, so i bent them out so its stable. Once you have your circuit placed correctly, hot glue it down, and cover the whole transistor, soldered part as strain relief and to prevent shorting. Then, pull a bit of wire back out of the hole in the lid so when you open the lid, it doesn't pull the wires. Push down the "flaps" from the hole around the wire to secure it, and then hot glue it. Now, close the lid and glue the "base" of the wires on the outside of the lid. Take your 2 thin wires, and hot glue them approx. every 1 in. along the heavy gauge wire (man it is getting old writing heavy gauge wire every time!) until you're at the top. The last soldering part is to twist your 2 LED's together, and trim and strip your 2 wires at the top of the heavy gauge wire. Solder the positive LED lead to the wire that was connected to the right side of the transistor (my red wire). Sloder the ground LED lead to the wire that was connected to the left side of the transistor, and the battery ground (my black wire). Then, wrap some electrical tape or heat shrink tubing around each lead and around the whole top part there, leaving the LED's exposed.

Step 5: Wrap the Flexi "Neck"

Take 2 colors of your cheap wire and take a long length of it. Glue the 2 wires at the base where the heavy gauge wire or flexi neck goes in. Wrap around with equal spacing until you get to the bottom of the black tape. Glue it there, and then take 1 wire color and glue at the bottom of the tape. Wrap with no spacing until you hit the LED's, and then glue it. You could get some inspiration for designs from bleep labs thingamagoop's Ledacle.

Step 6: You're Done!

It's done! You can use it for anything you need to light. I lit my fish tank at night with it for a neat affect. It is very bright, and lasts very long (as of writing i am on 2 days and counting with no decrease in brightness!). Any suggestions are welcome, and if you make one, please post pictures! If anyone wants to know how it works, simply ask in the comments and I'll put up another slide explaining it.

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    171 Discussions


    9 years ago on Step 1

    can someone please tell me the dimensions of the toroid as im trying to get one fom maplins?

    1 reply

    Reply 9 years ago on Introduction

    Well pretty much any size will work. About one-two centimeters is good. From a old computer motherboard you will get couple that works fine.


    10 years ago on Introduction

    can u give me an idea of the specs for the toroid when its made (meaning after the wiring...) i wanna build a smaller version of this so im just gonna get an already built one of these

    2 replies

    10 years ago on Step 2

    Add the length of the wires IS "Take 2 same lengths of wire " Recommend "Take 2, 10(??} inch lengths of wire" Bob

    1 reply

    Reply 10 years ago on Step 2

    That depends on the size of your toroid, just take enough to get 10 winds...


    10 years ago on Introduction

    This is a good instructable. I see you saw the 'Joule Thief' HOW TO in MAKE Magazine. One thing to note is that you should include a schematic. All these written steps are good, but they can get a little confusing. I had to link to THIS site to build mine properly.


    10 years ago on Step 1

    What size is the toroid?


    10 years ago on Introduction

    whats the purpose of the toroid in the circuit???pls help