This pocketsized flashlight packs more amphours per ounce into your pocket than anything you could buy... if you dare to make one.
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Step 1: "Make an LED Flashlight Out of ..."
You've seen them. They propagate like syphilis. They are Unoriginal LED Flashlight Instructables.
"Make an LED flashlight out of ...":
an Altoids container!
a Tic Tac container!
a Mini Altoids container!
an empty 9 volt battery container!
an Altoids gum container!
an empty film canister!
a used wad of toilet paper!
Well, this one is DIFFERENT. It's difficult, dangerous, and just plain time-consuming. So don't try this at home, unless your middle name is Danger. And you first name is Nerd. So, you're still interested? Ok, then. Step into the light.
Step 2: Lithium!
If you have played with lithium batteries before, then you probably know the deal. Lithium batteries have awesome ability to store energy for long periods of time. They hold a massive amount of charge. They can be recharged like no one's business. But they are also dangerous. Excellent. They can also be found for free. Even more excellent.
For the free-ist lithium batteries, try asking at the local electronics store where they have recycling bins. Sometimes the guys are ok with you taking home some "dead" laptop batteries.
What do you want with a "dead" laptop batttery? Well, don't get me started on the subject of laptop batteries, else I'll wind up in Guantanemo Bay. Let's just say that it behooves certain people to make you think your laptop battery is dead when it really isn't. Of the laptop batteries that I have taken in, only 1 in 5 is truly anywhere near dead.
Step 3: LED's
So, I have a lithium battery. Now I need some LED's. Darn. I just sold off my LED collection to pay my light bill, and this contest just appears out of nowhere. I appropriated the LEDs from this 3 million rupee flashlight I made two years ago.
With the help of a propane torch-heated exacto knife, removing the LEDs wasn't too hard. It used up a lot of elbow grease, for sure. But in my Mountain Dew fuelled modding frenzy, I couldn't stop to buy some new ones.
Step 4: Making the Light Assembly
One of the LED's didn't survive the surgery. I saved it, anyway, to be used as a spacer.
With some sandpaper, I removed the rims from the LED's so they could be packed together closely, in a honeycomb pattern. I put the dead LED in the center.
I used hotmelt glue to tack each LED onto the center LED. On each LED, I oriented the cathode towards the center. Once assembled, I wrapped some packing tape for temporary suppport.
Step 5: Soldering
So, now take a look at the pics for some improvised contruction techniques - safety of which is unknown. I can't seem to make pic notes, so I'll describe:
1. solder the cathodes together and solder a wire
2. dab with hotmelt and cover with teflon tape or some other insulator that won't melt. Heavy craft paper or index card would work
3. put a dot of copper foil tape in the center
4. solder a 15 ohm resistor to each anode, and join them all on your center copper tape pad.
5. Solder a wire to the center pad.
6. Now you have two wires. One for the common cathodes, and one for the anodes. The LED's are all in parallel, with a 15 ohm resistor on each one.
Step 6: Battery
Now back to the battery. We'll add a recharge port, first. Then we'll solder the circuit together. I used a pic and a mosfet to control the power, the only reason being I could use a smaller switch. Talk about Rube-Goldberg. I didn't even put in any fancy flashing patterns or dimming features. It turns on, and it goes to sleep. See pics for details.
1. After insulating the rim of negative terminal at the top, I carefully cut out the protruding bulk of the positive terminal. Why? to save a millimeter or so of length. Yeah, that's probably not worth the risk.
2. I carefully filled in the depression with hotmelt glue, then I carefully soldered a female SIP header pin and wire to the remnants of the positive terminal.
3. I carefully slipped the rest of the header over the soldered pin, then soldered the outer two pins down to the rim of the negative terminal.
Notice how many times I used the word "carefully." If you short the battery terminals, the battery could instantly heat up to the temperature of thermite, fusing the battery to your skin only to explode in your face just a few milliseconds later, causing permanent blindness! Or you might see a small spark, hear a small click, the safety valve may or may not pop followed by a dribble of clear fluid, indicating that you have just killed your battery.
Step 7: Circuit and Putting It Together.
Because I programmed a PIC, I did not make a schematic. But I'll show you a picture, anyway. The big chip is the PIC. It's a DIP part, but it's sanded down so it's wafer thin. The smaller chip is an SOIC n channel mosfet. I soldered everything that is grounded or NC directly to the battery. The button is also soldered to the battery. Well, half of it is. The other half is insulated with teflon tape.
pic2: I used a dab of hotmelt glue to adhere the LED assmebly, then carefully soldered the wires.
pic3: Typically, on a project like this, I'm shooting for a 50-50 chance of success. I'm kinda winging it. I'm not sure how many watts the resistors can handle. The mosfet isn't a logic level device. So on, and so on. Well, I pressed the button, and woot. Works perfectly.
Step 8: Finishing
The light fixture and recharge port need to be epoxied for structural support. The smd resistors are especially prone to cracking. Even more importantly, all exposed parts of the positive terminal and any wire/lead/pin connected to it must be protected from accidental short circuit. So I didn't leave this one all up to hotmelt glue.
I used this stuff. It's called Kneadatite. It's like modelling clay, but it's really epoxy that sets in about 12 hours, or so.
Hope you enjoyed my latest adventure in electronics.
See ya next time!