Full Circle: A Hand Cranked Power Supply

 

In my first assignment for Fabrication I created a hand-cranked flash light with parts from the junk shelf. For this final assignment I thought it would be wonderfully fitting to expand on that concept and create a hand crank that could power my other assignments, or any projects in the future.

Circuit

Bringing the concepts from Basic Analog Circuits I created a simple voltage regulator, with power coming in from a DC motor.

Motor

I tried two separate DC motors with this circuit, a 12V 20 RPM metal gearmotor and a 12V 60RPM gearmotor. I tried the 20 RPM first since I thought a slow crank cycle would be tactilely pleasing, but it turned out that the gear ratio was far too high to comfortably turn with the handle I made. 60 RPM was a lot easier to turn, and worked out great in the end.

Mounting the motor

First, I needed something sturdy to mount the motor and circuit to. I fell back on good ol’ faithful 2×4. With a 37mm mounting hub for the DC motor, a prototyping board for the circuit, and a handful of M3 machine screws, I measured out the mounting holes and drilled 3mm holes into the 2×4.

Mounting to the Motor

It speaks to my progress in the course that the first time around I did this I hacked together a terrible motor mount with some scrap pieces I found in the junk shelf, but this time around I knew immediately that I needed a 5mm mounting hub. I used the same trusty aluminium bar from the first assignment (hurrah recycling), with new holes for the hub.

The spinning wooden handle was created in a similar way to the original, in that it uses a machine screw as an axle, secured into place with washers and loosely fitting nuts. A slight difference in this version is that I used Loctite to secure the nuts in place, hopefully insuring that no matter how frequently the handle is turned the nuts won’t budge.

Modularity and Wrapping Things Up

The week 4 advice to “find your standard” rings true here. I’ve been trying to create my electronics this semester with modularity in mind, or at the very least the ability to change power supplies. I bought a pack of DC male-female connectors (the type you find on many ‘wall wart’ power supplies, and Arduino Unos) with screw terminals, and tried to use them as much as possible in recent projects.

The self-imposed vague constraint above paid off with this project, as now, with a variable power supply, I can retroactively make all of my fabrication projects sort-of interactive, or at least human-powered, which is something.

Though I did not intentionally plan this from the beginning I reckon it is a good way to bring all the projects together; create a sort of cohesion. What’s more, considering that my first project was human-powered, hand cranked, and focussed on green energy, it seems like a lovely storybook ending. Thus, we have come full circle. Ha.

 

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