The Harbor Freight 27 LED flashlight, Item # 67227 or 69567 is a great deal, even if you just plan to use it as a flashlight. The list price is $5.99, but it's very easy to find coupons online or in your local newspaper ad to get the flashlight for $3.50 or less. And it comes with batteries!
The flashlight is an absolute godsend if you have a use/need for high brightness LED bulbs. The 27 LED's in the flashlight each have a forward voltage of 3v and a forward current of 50mA. In comparison, white LED's cost $2.50 for a package of just 2 at RadioShack.
With just a soldering iron, a multimeter, some wire, and a "third hand" (either store-bought or homemade), you can extract all 27 LEDs for whatever nefarious purpose should suit you.
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Step 1: Take the Flashlight Apart
For some reason, my flashlight body is orange. The newer ones have blue bodies, but are otherwise the exact same.
Unscrew the three Phillips head screws on the back cover, then pry the back cover off with a flat-bladed screwdriver. This will reveal four more Phillips head screws--remove these. Remove the batteries also.
The top cover, lens, and reflector should all be fairly straightforward to remove. After removing the batteries, snip the two wires leading between the circuit board and the battery compartment.
The magnet on the back of the cover is useful for retaining the screws. Keep the magnet, screws, and hooks for other projects.
Step 2: De-solder the LEDs
The three LEDs forming the small light have long leads. Just de-solder them and wriggle them out by the leads.
Removing the remaining 24 LEDs is also straightforward. For each LED, apply your soldering iron to both leads simultaneously. Wriggle the LED out by pulling on the bulb--you might need to use needle-nose pliers for this. It helps to have the circuit board held securely by a third hand tool or a vise.
Step 3: Extend the Leads on the Short-lead LEDs
The 24 LEDs you extracted from the short part of the board have very short, stubby leads. They're not easy to connect to other things. And they won't necessarily fit in through-holes on other circuit boards where you may want to use them.
We can extend them pretty easily though.
Step 4: Make the New Leads
Find some solid wire. I used bits of 24AWG speaker wire that I stripped the insulation off of. You could even use resistor leads clipped from previous projects.
Using the tip of needle-nose pliers, form the end of each into a small loop or shepherd's crook shape.
Step 5: Add the New Leads to the LEDs
Slide the loops you have just formed over the stubby leads on the bulb. Smash each existing lead flat using a flat-bladed screwdriver so that it holds the loop in place.
Then solder the bits of wire you have just made to the existing leads on the bulb.
Step 6: Determine Polarity and Clip the Negative Lead
Bend the new leads straight, giving the appearance of a new LED bulb you'd buy at RadioShack.
Use a multimeter to determine the polarity of the LED. To indicate polarity, convention holds that the negative lead is shorter than the positive one. Clip the negative lead so that this is the case.
Step 7: Use the LED Bulbs in Your Own Projects!
The LED bulbs have a forward voltage of 3 volts and a forward current of 50 mA. Enter these specs, the number of bulbs you plan to use, and your supply voltage at http://ledcalc.com in order to determine which ballast resistor your application needs.
I used 4 of the bulbs to upgrade my car radio after the incandescent bulbs started burning out. LEDs do not burn out, so I shouldn't have to change another radio bulb for the life of the car (and I fully intend to keep the car for twenty years or more). I plan to use the LEDs to replace the other dashboard and interior bulbs as they burn out.
(DO NOT connect these LED bulbs directly to car voltage--they will overheat and die very quickly. You have to use a ballast resistor.)
Maybe you have a more exciting use for your LED bulbs. Tell me about your projects!