Enerwheel

full_kinetic_demo.gif

For our Kinetic Energy assignment, I collaborated with Dan Oved to build something that would turn muscle power into usable electricity.

–Process–

We started off by brainstorming on a few concepts for generating light from human motion.

Hand cranked music box

The first thing we explored was turning a hand-crank music box into one that emits light in sync with the music.

We would connect a motor to the end of the crank shaft and have that generate electricity.

Wheel chair powered light

We explored using the wheelchair on the ITP floor for kinetic energy – it could work in one of two ways.

When the user pushes on the wheel, it would rotate a DC gear motor attached via a belt, to generate electricity.

Or, when the user pulls the break pedal, it would move a gear motor attached to a rubber wheel down to have the rubber wheel touching the wheel of the chair, the resistance causing it to break and generating electricity.

Electric Poi

Our final idea came from something I’d seen in India, a variant of slingshot where farmers spin a weighted ball attached to a rope around in circles, in order to keep birds away from their crops. Back home its called a gofan but it closely resembles a Poi performance art prop. We thought of turning this swinging motion into kinetic energy. There would be a handle with a rope and wire coming out of it connected to a ball with a light in it. The rope would be physically attached to the shaft of a gear motor which would be inside of the handle; when the ball would be swung around, it would cause the shaft to rotate, thus generating electricity. This electricity would be outputted back to the wire which would power the light.

Poi performance

We then realized this would likely get tangled, or have difficulties rotating the shaft if it was attached directly to it; instead we decided it would be better to attach the rope to a plate or L bracket attached to the shaft, which would increase the torque and force the shaft to rotate.

We decided to go ahead and test this idea for feasibility. We did some calculations to narrow down on the exact motor we would require in terms of RPM and torque. The main components of the math were the length of the string and the weight of the light object attached to it. As soon as the motor arrived, we attached a weighted object to it with a coupler and a wire. We realized the wire wasn’t actually moving the motor shaft but rather just spinning at the very point where it was tied to the motor. It snapped in no more than 4-5 rotations.

We had to think of something else! Thats when I recalled of seeing a make shift and re-purposed, rural Indian toy where these kids in rural areas would essentially find anything which is round and attach it to a stick and run around the village rolling that wheel on the ground. We thought of building on that with a motor at the center of that wheel which powers an LED strip stuck to the periphery of the wheel itself. This meant that we don’t have to worry about mounting a slip ring in between the motor and the shaft or light.

–Parts–

Selecting the motor

To power the lights, we would force a DC gear motor to turn and tap into the electricity it generates. We chose a 127 RPM Mini Econ Gear Motor from ServoCity, because it had optimal RPM and a low torque of 9,602 kgf-cm.

The 127 RPM dc gear motor we used from Servo City

We would use a .770” Pattern Clamping Hub which would attach to the shaft and rotate to generate torque:

The clamping hub

CAD design

Servo city had provided detailed 3D files for the motor and the coupler on their website. We thought it would be best to plan, troubleshoot and refine the idea in CAD itself to save on time and fabrication. We used Rhino to design the wheel around the selected hardware and mounting brackets.

2
Cross section of the wheel at the spokes

Prototyping the circuit

Next it was time to build a circuit that would simulate the power generation. We used 4 diodes as a bridge rectifier so that no matter which way the motor was turned, the current would flow through the circuit in the same direction. We used a bunch of capacitors in parallel to smooth out the current and store energy when the wheel stopped turning, enabling the lights to stay on. We used a 12v white analog LED strip since it has the same voltage rating as the DC Gear Motor.

The prototyped circuit with a bridge rectifier

We were able to test the circuit successfully. Turning the motor in either direction generated power to turn on the lights:

Fabrication

We converted this 3d model into slices of 3/4 inch to cut it on the CNC Router

Then we glued it all together and let it sit overnight

IMG_20180211_195855369
The engine mounted to the wheel. This would allow the circuit to rotate with the wheel without the need for a slip ring.

We found a tripod leg on the ITP junk shelf and thought it would be perfect as a stick that drives this wheel. Plus it was already well finished and accommodated the motor’s mounting bracket perfectly

IMG_20180211_223050632.jpg
match made in heaven!

Fabricating the circuit

Next it was time to build the circuit that could withstand a series of rapid rotational turns. We designed something simple in EagleCad

The circuit with the bridge rectifying diodes and 47uF capacitors in parallel

kinetic_board_and_fabricated_scaled

soldered_bottom_hud86e04b2e53c6c6eadbb581cb21a0d09_3524068_520x0_resize_q75_lanczos_center.jpg
The circuit with the capacitors in parallel and bridge rectifying diodes. Yellow wires would go to the motor and accept either polarity, and red and black wires would be power and ground for the lights.

We tested the circuit with an external 12V power supply, and also tested reversing the polarity of the power supply to see if the bridge rectification worked, and were glad to see that it did.

IMG_20180212_204101612.jpg
Sticking the LEDtape and routing the wire. We also used 3M’s friction tape to add some traction

–Putting it all together–

After coating the wheel with black spray paint, it was time to assemble everything and test it all.

The spray painted wheel with circuit attached
Yellow wires pass through the center and are attached to the DC gear motor’s power and ground.
The shaft of the motor coupled to the rod; when rolling the wheel the torque would cause the engine to generate power.
Getting ready to test everything

Dan testing the wheel
It worked!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s