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Discussion Starter · #1 ·
I looked high and low for a good hand-crank generator to no avail. I wasn't asking for much: high power (~10W) and rugged (metal gears and crank). Not satisfied with the market, I decided to build my own.

My design was to be simple: Take a geared 24VDC motor, add a crank, send it through a voltage regulator and put out [email protected] I purchased a 24VDC 110RPM geared motor (all metal), a casement window crank, an LM7805 voltage regulator and PVC pipe to house it all.

This worked quite well...5V at a slow pace on my meter. The problem, I discovered, is that most low-power devices aren't designed to draw 10W (my cell phone draws 2.5W). To make expedient use of my hand crank, I decided I'd need intermediate storage.

Enter the Maglite. A 3D Maglite with a TerraLUX 3W LED would serve nicely as a battery holder. I replaced the 3 D-cell batteries with 5 1/2 D-cell NIMH, giving me ~6V. I ran a wire down the Maglite tube to get both terminals at the end-cap, then wired them to a barrel jack; this jack would provide power to my devices and be used for charging the batteries in the light. This jack proved very difficult to get right. In the end, I replaced the negative battery terminal spring with a spring that just fit around the barrel jack. This gave enough clearance for the wire to prevent it from being eaten (as it was with the stock spring).

The addition of batteries complicated things quite a bit. Unless this whole project was to be an expensive firesteel replacement, I needed a charge controller! I purchased a MAX712 IC, all of the caps/resistors listed in the datasheet, a prototype board and a 12V regulator. After an hour or so, it was all wired up and ready to test; it worked like a charm. I have the charge circuit set at C/3 which, according to my calculations, is approximately 11W. You can definitely tell when it goes from fast-charge to trickle.

I added a barrel jack and a switch to allow the use of a wall brick (if you don't feel like cranking), as well as a second circuit that supplies USB power hooked up to my iPhone cable. I'll leave this second circuit out of the final product, since it really is silly to crank directly to a USB powered device (2.5W). I think the final housing will be the tube of a second Maglite, since they're very rugged (I don't like plastic).

I have the circuit ready for printing, so once I get some motivation I'll etch it out and make it pretty. Total cost of the project was...more than I care to think about, but I'd estimate I could build one for about $100. I'll report back when I build the final project.

Just figured I'd share it with the board in case anyone else is looking to do the same. ;)
 

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Instead of batteries and a charge controller, why not a couple of large capacitors between the motor and voltage regulator so you dont have to constantly crank? Maby a little cheaper and a lot simpler.
 

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A friend of mine is putting his designs into production right now in Virgina. They should be avail in the next couple of months. They will be avail. both as a hand crank and a bicycle version and will put out a tremendous amount of power compared to past designs by other people. The magnets and windings in these things will floor you. He will be taking orders as soon as they are ready to go. All american made and affordable. I should be able to take orders for him very soon. Will keep you all posted should you be in the market for a quality unit
 

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Discussion Starter · #4 ·
The charge controller for the batteries allows me to limit the draw on the motor to my target 10W, making the cranking smooth. I could've used a cap instead, though having a battery bank has other benefits:

  • You can charge it here and there as time or energy permits.
  • I can charge my bank from other sources (wall wart, solar panel).
  • I get a full charge when walking into the woods, so I can use it as a simple battery extender for my phone for shorter trips.

The other upshot is that I get a rechargeable flashlight out of the deal. I may add a large cap anyway, just to keep things smooth when cranking isn't continuous.

Once I'm "finished" with the project, I'll work on adapting a geared spool for generation. The concept is to run paracord through a block on a tree branch, and using my pack's weight to unspool the cord. As the cord unspools it spins the crank, generating power while I'm doing other things. I'll likely need a brake on the spool to regulate the speed, but who knows.
 

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Used a two handle sit down crank for power for radios in the field in the army.

I do not know any details of power etc. but they were small and could hold a charge (capacitors I guess) for about an hour of morse code operations.

later
wayne
 
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