Step 2: Parts and Tools
The parts for the step-up circuit can be obtained from an electronics distributor such as Digikey.
U1 -- MAX756 3.3V/5V step-up DC-DC converter, 8-pin DIP package [Digikey# MAX756CPA+-ND]
C1 -- 0.33 F 5.5V capacitor, coin package [Digikey# 604-1024-ND]
C2,C3 -- 100 uF 6.3V aluminum electrolytic capacitor, mini radial [Digikey# P803-ND]
C4 -- 0.1 uF 25V ceramic general purpose capacitor, through-hole [Digikey# BC1148CT-ND]
L1 -- 22 uH RF choke, axial [Digikey# M8138CT-ND]
R1 -- 1k, 1/4W general purpose carbon film resistor, axial [Digikey# 1.0KQBK-ND]
D2 -- 1A 20V Schottky diode, axial [Digikey# 1N5817GOS-ND]
D3 -- If you are not able to recycle the original LEDs in the flashlight because the leads were clipped too short, you can use any 2 mA LED, round T1 3mm [e.g. Digikey# 475-1402-ND]
Dynamo keychain flashlight
I used a dynamo LED keychain flashlight which was marked as AIDvantage and made by LTA, Inc. (item# 02119) for this project. There are a variety of these sized flashlights on the market made by different manufacturers -- I've seen them at grocery stores (Giant on the East Coast) and computer stores (Microcenter). You can find them online by Googling: dynamo keychain flashlight. They usually cost less than $5.
I discovered there are some minor variations between flashlights made by different manufacturers. One flashlight I got at Microcenter did not have a circuit board for the LEDs -- the LEDs were just soldered directly to the battery. This LED circuit board is nice but not required. If you find that there's no separate circuit board for the LEDs, you can just solder the respective positive and negative leads of the LED+resistor combo and output cable together. A little hot glue inside the faceplate near the LED and output cable can give the assembly some mechanical strength. The other variation was that leads on the switch on this version were also soldered slightly differently to the battery. Otherwise, it was pretty much identical.
I used a USB A male to mini-B USB male cable scavenged from a dead MP3 player as the output cable. I chose this cable because the mini-USB input is common for small circuits. Since there are 4 connections inside this cable, you have to figure out which wires are the positive & negative leads. However, you can use any output cable type you want if you know the polarity.
To test the circuit, you will also probably want to have the complementary jack available for the output adapter. I de-soldered the mini-B receptacle from the dead MP3 player and connected red and black wires to power 5V and ground pins, respectively.
You will need the following tools to build and test the modified dynamo:
-- wire stripper
-- soldering iron, solder, & flux (this Instructable assumes you have soldered before)
-- voltmeter & test leads
-- small Phillips screwdriver (for opening the flashlight case)
-- electrical tape
-- small wire cutters
-- small pliers
-- tweezers (optional, but recommended)
-- adjustable arms vise, third hand tool (optional, but recommended)
-- small flathead screwdriver (optional, but recommended)
-- hot glue gun (optional, but recommended)
-- hobby knife (optional, but recommended)