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Step 2Build the charger circuit
The charger circuit is pretty simple. It consists of:
1. A diode bridge to turn the AC voltage from the generator into rectified DC.
2. A rechargeable battery to level out the voltage and hold excess generated power when nothing is hooked to the USB port. You could use a big capacitor too, but batteries offer a more predictable voltage level.
3. A boost converter to bring the low voltage up to 5VDC for USB charging
4. A USB plug.
I've drawn up the circuit in EAGLE, a program that I highly recommend. You can download it for free from cadsoft.de. The schematic and single layer board layout are attached. The actual use of EAGLE and the board manufacture are beyond the scope of this instructable. Many great instructables are out there to cover these topics. See this one for example, on how to make PCBs in your kitchen.
The parts list for the charger circuit (quantities in bold):
1x L6920 Adjustable output step up DC converter (1V minimum input, Datasheet here)
Digikey# 497-4593-1-ND
4x 1N4148 switching diodes (I used tiny SOD523 smds, but you can sub in what you have handy)
Digikey# 1N4148WTDICT-ND
2x 10uF ceramic or other low ESR capacitors (I used 1206 smds)
Digikey# 39901299-1-ND
2x 100k thin film resistors
Digikey# P100kFCT-ND
1x 10uH wirewound inductor
Digikey# 490-2519-1-ND
1x USB female Type A smd connector
Digikey# AE9924-ND
Below you can see the schematic and board files, and jpegs of them as well. The tough part is making a good PCB in your kitchen that has traces small enough for the TSSOP package of the L6920. As you can see in the pic, I made 4 boards at once since each is so small.
The trick to putting it together is to start in the middle and move your way out, begin with the L6920, and add the SMD discretes as you go. A pair of tweezers is essential, along with good eyes or a magnifying glass, bright light, and a steady hand. Don't worry about getting too much solder in there, use your solder wick to clean up any accidents, and check your work with a multimeter after every step. Practice makes perfect.
1. A diode bridge to turn the AC voltage from the generator into rectified DC.
2. A rechargeable battery to level out the voltage and hold excess generated power when nothing is hooked to the USB port. You could use a big capacitor too, but batteries offer a more predictable voltage level.
3. A boost converter to bring the low voltage up to 5VDC for USB charging
4. A USB plug.
I've drawn up the circuit in EAGLE, a program that I highly recommend. You can download it for free from cadsoft.de. The schematic and single layer board layout are attached. The actual use of EAGLE and the board manufacture are beyond the scope of this instructable. Many great instructables are out there to cover these topics. See this one for example, on how to make PCBs in your kitchen.
The parts list for the charger circuit (quantities in bold):
1x L6920 Adjustable output step up DC converter (1V minimum input, Datasheet here)
Digikey# 497-4593-1-ND
4x 1N4148 switching diodes (I used tiny SOD523 smds, but you can sub in what you have handy)
Digikey# 1N4148WTDICT-ND
2x 10uF ceramic or other low ESR capacitors (I used 1206 smds)
Digikey# 39901299-1-ND
2x 100k thin film resistors
Digikey# P100kFCT-ND
1x 10uH wirewound inductor
Digikey# 490-2519-1-ND
1x USB female Type A smd connector
Digikey# AE9924-ND
Below you can see the schematic and board files, and jpegs of them as well. The tough part is making a good PCB in your kitchen that has traces small enough for the TSSOP package of the L6920. As you can see in the pic, I made 4 boards at once since each is so small.
The trick to putting it together is to start in the middle and move your way out, begin with the L6920, and add the SMD discretes as you go. A pair of tweezers is essential, along with good eyes or a magnifying glass, bright light, and a steady hand. Don't worry about getting too much solder in there, use your solder wick to clean up any accidents, and check your work with a multimeter after every step. Practice makes perfect.
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http://www.ladyada.net/make/mintyboost/
Otherwise, the cost of the components for my circuit is negligible, like less than $10. I can dig around and see if I can scrounge a complete board. Honestly I got sidetracked from this project and haven't looked at it in years so I can't be sure I even have any of it still. If I do, it would be better that someone use it than it sit in a drawer in my basement so I would be willing to donate to a good cause. What is your plan for the circuit?