Shaky Leg Power Generator

Anyone who has spent any length of time near me knows that my leg shakes. Friends and family typically start to notice when the dining table starts to shake. What tips off coworkers is usually a shaking monitor and a subtle ripple breaking the surface tension of their coffee. After a while they realize it is not a mild earthquake, it is just me.

Most people can politely put up with it for so long. After a while even the most mild-mannered person will turn to me and say "Randy. Stop it!" I sympathize with them and do my best to keep my heel flat on the floor. It takes a lot of willpower to stay grounded. If my mind is left to wander, my leg starts to chase after it.

I'm not sure if at this point I will ever get to a place where my leg will ever stop shaking, but I can at least make the most out of it. Rather than radiate nervous energy pointlessly out into the aether, I have made this device to harness my involuntary leg-shaking and convert it into useful energy. From now on I can harness my anxious disposition to provide safe and clean energy to recharge all of the USB devices in our lives. Since I am now providing a useful service it is my hope that people will be less annoyed when I start to shake - or so one can dream.

You will need:

(x1) Expression pedal
(x1) 3D printer (I use a Creality CR-10)
(x1) Stepper motor
(x1) PCB
(x1) LM7805 voltage regulator
(x1) electrolytic capacitor (10uF, and 1,000uF)
(x1) ceramic disc capacitor (0.1uF)
(x8) 1N4007 diodes
(x2) 15K resistor
(x1) USB extension cable
(x7) 1/2" spacers
(x7) 3/4" metal screws
(x1) M4 x 8mm nut and bolt
(x4) M4 x 12mm nut and bolt
(x4) 1/4" plastic spacers
(x4) M3 x 12mm nut and bolt
(x1) 3/4 diameter x 0.062 gauge wire compression spring
(x1) Acrylic disc (cut using attached template)
(x1) Felt disc (cut using attached template)
(x1) Hot glue gun

(Please note that some of the links on this page contain affiliate links. This does not change the cost of the item for you. I reinvest whatever proceeds I receive into making new projects.)

Remove the screws from the underside of the expression pedal and open the case.

Pull the existing lever arm off of the potentiometer shaft on the inside of the pedal.

Remove both of the potentiometers from the inside of the pedal.

Trim away all of the wires attached to the small circuit board on the base plate.

All of the initial circuit should now be cut free.

3D print the motor mounting bracket and lever arm using the attached 3D models.

Attach the Motor to the motor bracket using 12mm nuts and bolts.

Position the shaft of the motor on the inside of the pedal where the potentiometer with the lever arm was previously situated.

Using the bracket's mounting holes as guides, drill two 3/16 holes in the body of the pedal.

Be careful not to drill all the way through into the foot pad.

Affix the motor mount to the body of the pedal using 12mm nuts and bolts.

Slide the new lever arm onto the motor shaft such that the plastic pin attached to the top of the pedal is centered in the lever's channel.

Build the power regulation circuit as specified in the schematic.

Basically, there are are two bridge rectifiers - one for each coil of the motor. The 1000uF capacitor is used to store and filter the electricity generated to create a smooth signal which is then converted to a steady 5V by the LM7805 voltage regulator. The 10uF and 0.1uF capacitors are additional power filtering at the regulator stage.

The two resistors are required for pulling the data and clock lines low while charging USB2 devices. Without these, your device probably will not charge.

Cut the USB cable in half and expose all of the cable's four wires.

Attach the USB cable to the circuit board as specified in the schematic.

Drill a 3/16" hole in the center of the plastic contact pad on the body of the expression pedal. Mount the acrylic disc to the top of this pad using a 8mm nut and bolt.

Glue the felt disc to the felt pad that is directly opposite the plastic contact pad.

Once the glue is dry, place each end of the spring around each of these discs to hold the spring in place.

Solder the motor wires to the circuit board as specified in the schematic.

Place the circuit board centered atop the pedal's base plate on the side opposite from the existing small circuit board.

Make marks for each corner mounting hole and then drill them using a 1/8" drill bit.

Mount the circuit board to the base plate using 1/4" spacers and M3 x 12mm nuts and bolts.

Hot glue the USB cable to the base plate to keep the wires from snapping off the circuit board.

Close the case up using 1/2" metal spacers and 3/4" screws.

Plug in all of your devices and get charging. Don't expect a rapid charge from this device, but a slow steady trickle over the course of an anxious day.