Introduction: Shaky Leg Power Generator

Picture of 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.

Step 1: Go Get Stuff

Picture of Go Get Stuff

You will need:

(x1) Expression pedal (RadioShack #55071404 - online only)
(x1) 3D printer (RadioShack #277-224)
(x1) Stepper motor (RadioShack #273-767)
(x1) PC Board (RadioShack #276-150)
(x1) LM7805 voltage regulator (RadioShack #276-1770)
(x1) 1000uF capacitor (RadioShack #272-1032)
(x1) 10uF capacitor (RadioShack #272-1025)
(x1) 0.1uF capacitor (RadioShack #272-135)
(x8) 1N4007 diodes (RadioShack #276-1653)
(x2) 15K resistors (RadioShack #55049437 - online only)
(x1) USB-A to USB-B extension cable (RadioShack #26-1709)
(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

Step 2: Open the Pedal

Picture of Open the Pedal

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

Step 3: Remove the Lever

Picture of Remove the Lever

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

Step 4: Remove the Circuit

Picture of Remove the Circuit

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.

Step 5: 3D Print

Picture of 3D Print

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

Step 6: Fasten the Motor

Picture of Fasten the Motor

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

Step 7: Place the Motor

Picture of Place the Motor

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

Step 8: Drill

Picture of Drill

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.

Step 9: Mount

Picture of Mount

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

Step 10: Attach the Lever

Picture of Attach the Lever

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.

Step 11: Power Circuit

Picture of Power Circuit

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.

Step 12: Cut the Cable

Picture of Cut the Cable

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

Step 13: Attach

Picture of Attach

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

Step 14: Spring

Picture of Spring

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.

Step 15: Attach the Motor

Picture of Attach the Motor

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

Step 16: Drill

Picture of Drill

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.

Step 17: Mount the PCB

Picture of Mount the PCB

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.

Step 18: Case Closed

Picture of Case Closed

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

Step 19: Use It

Picture of Use It

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.


zaxs18 (author)2016-12-14

umm where do i get a 3d printer? ): i wanna make it ];

randofo (author)2016-08-22

I am not sure. It would depend what the mechanism and space inside the sustain foot pedal looked like.

mchau2 (author)2015-12-29

hm i am not a shaky leg kinda person... but some of my classmates are.... their (bad) habit can finally put in good use!!

THE17MITESH (author)2015-08-12

Can any1 tell me the approx cost of this project ? plz mail me on

Wazzupdoc (author)2014-09-21

Great device. Would like to see a non-3d printer version. Also, check this out for info on restless leg syndrome:

jec0435 (author)Wazzupdoc2015-07-27

FYI, bouncy/shaking leg, is totally different than Restless leg syndrome. ;)

Wazzupdoc (author)jec04352015-07-28

Harnessing energy, either way.

hasona (author)2015-04-12

i dont get the part of Arduino

bigfoot03242 (author)2015-03-03

Great Idea! I have driven people nuts with my leg shaking. I wish I had thought of it.

hasona (author)2015-03-01

akshayt2 (author)2015-01-31

Am trying this for the first time and have been able to get a hold of all the components. The issue is I don't know how to solder the components that well and moreover, the idea behind the 0.1 uF and 10 uF capacitors confuse me. The picture shows there is a 1 uF capacitor, so I'd like to know if fixing one 1 uF capacitor is sufficient for the circuit?

techboy411 (author)2015-01-11

Randofo, if you want, use a USB powerbank connected to the output, and you have a "Shaky-foot"-charged USB battery.

EnanS (author)2014-12-11

I am making this for my 8th grade science fair, except i am hooking up a bike instead of a expression pedal. Also this my first complex electrical project, how did you connect the diodes, capitators, etc. to the wires?

BenP4 (author)2014-11-20

Is there any way that this could be made by using a bicycle dynamo instead of a stepper motor?

iam_maker_leo (author)2014-11-18

Amazing... Great...

I want to try it....

kingofrandom92 (author)2014-11-11

It says you used a 1000uf capacitor but what voltage is it? Once its fully charged what do you say you get as a charge out of it(a few minutes with the LM7805 voltage drop) ??? Working on a project could really use a response quick. i am actually making a very similar project using electro magnetic coils rather than a motor. very similar setup and this is the fist time seeing your work. I enjoyed it.

steinie44 (author)2014-09-25

Great. Now come up with one that my wife can talk into, and we'll be off grid in no time.

deluges (author)steinie442014-10-29

I laughed so hard at your comment

Thanks for making my day :)

leadzeplin (author)2014-10-08

smart project

tkleinauskas (author)2014-10-06

Good job!

clazman (author)2014-09-23

The thoughts of power are interesting. How about designing one of these that would have auto load compensation. It would maximize energy extraction plus adjust to the output potential of the individual. ;-)

Very nice start!

Omit (author)2014-09-22

great idea !! hey on an old show called the wood wright shop he made a foot powered wood lathe

e-gr2learn (author)2014-09-21

Thank you, Rodolfo, for "liberating" us, the shaky-leg folks. Am used to my husband's gentle teasing that, "your motor's running". And I tease him back on the rarer occasions that his leg is also bouncing, with the rejoinder, "...and so is yours!" Don't know if it'll ever go away completely; at age 69 I've had the bouncy-leg thing for decades. (It just made me more self-conscious in my teens & 20's.) Keep that leg charging ahead (pardon the pun.....) Now I've just got to build the device.

anguevuberwald (author)2014-09-21

love this. I'd buy one!

Pothuset (author)2014-09-19

Good work.

LockonStratos (author)2014-09-18

Fantastic project~

syates3 (author)2014-09-18

I have the same issue with shaking my leg, I'm doing it right now infact, annoies everyone near me hell my roomate once told me he could hear it threw the walls. So this is something I might make just for the sake of having a use for my leg shaking lol.

ganderson12 (author)2014-09-18

It's getting harder and harder to find cool instructables like this one, but that don't require 3D printing something or another. It's not like every small town local library has a 3D printer for public use. That's a decade or two away yet, I'm sure. I'll have to see if I can't rig up some alternative parts because I have the exact same issue with my leg; drives my wife nuts. I'd love to be able to tell her I'm just charging my laptop.

naught101 (author)ganderson122014-09-18

You can get a 3Dprinter for $200: . If you don't have $200, band together with a few others and get one - you're gonna get more value out of it if you're learning and building with others anyway. And if you're the only one in your town, you can offer the service of locally printed parts, and make back some of your money :)

ganderson12 (author)naught1012014-09-18

That'd be a good idea, to offer the service to my community. But then if a fellow had a couple hundred bucks to toss around on a novelty whim like building a shaky leg power generator, then he wouldn't have much use for a site like instructables in the first place; he could just up and buy whatever it is this site would teach him how to build. :P

randofo (author)ganderson122014-09-18

You could use somewhere like shapeways to print it or some carved wood. The parts are really not all that complex at the end of the day.

ganderson12 (author)randofo2014-09-18

Yeah, they don't look too terribly complicated. But I've never even heard of Shapeways. I'll have look that up to see if they have a website I could order from.

bholmes451 (author)ganderson122014-09-18

I used 1x2 wood furring strips to construct my first 3d printer. Carved wood shapes work very well for all sorts of things but many people have forgotten the fact in this age of plastic and circuit boards.

ClareBS (author)2014-09-18

Excellent instructable for alternative power generation.

You might have restless legs syndrome (I do). Check out the RLS website, it's very good. rls dot org

Is it okay if I put a link to your instructable on their discussion board? I might at the very least give some people a laugh.

randofo (author)ClareBS2014-09-18

That would be fine by me.

ClareBS (author)randofo2014-09-18


4lifenerdfighter (author)2014-09-16

Why do you use all RadioShack parts? Why not order from some place far cheaper like SparkFun or others? Not saying you're wrong here, I just find it interesting that you chose to use all parts from RadioShack.

It's sponsored by radioshack. I highly doubt he actually bought the 3D printer that was linked. Still a great idea though!

randofo (author)Mig Welder2014-09-18

Yes. We actually have one of the Afinia printers. We used it in a number of projects. The bed size is relatively small but the print quality is good and it's a workhorse. We have printed a lot of stuff with it over the course of this year and it just keeps running.

randofo (author)4lifenerdfighter2014-09-16

Radioshack has sponsored this project.

naught101 (author)2014-09-18

Why are you using a stepper motor? Wouldn't a simple DC brushed motor be a lot easier? (I would have thought also more efficient, especially if you got a geared one)

randofo (author)naught1012014-09-18

It would be simpler, but would not be as efficient. The stepper has more coils and you can get much more power with each rotation.

ClareBS (author)2014-09-18

Excellent instructable for alternative power generation.

You might have restless legs syndrome (I do). Check out the RLS website, it's very good. rls dot org

Is it okay if I put a link to your instructable on their discussion board? I might at the very least give some people a laugh.

zack_man888 (author)2014-09-18

One improvement that would probably give you more power output is to use a rack and pinion to drive the motor shaft instead of the simple lever system. The rack would be attached to the pedal and the pinion to the motor shaft. That would give you several shaft rotations per pump instead of just one rot. per pump. Anyways, really cool project!

oppie (author)2014-09-18

Note on the schematic: USB had Data+ and Data- along with +5 volts and ground.

cindyssister (author)2014-09-18

I need four of these!!!

One for my husband and one for each of my sons.

They all start bouncing their leg if they sit still too long.

busko (author)2014-09-18

This would be great during power outages or if you are out somewhere where there is no place to plug in.

Radioactive_Legos (author)2014-09-18

This is great, Randy! Love it

damaltor (author)2014-09-18

Nice project! I think you missed a wire in your cirquit though, the one from the positive end of the rectifier to pin1 of the 7805. connecting only the ground will probably not suffice :)

Thanks for sharing!

randofo (author)damaltor2014-09-18

Good point. Fixed and updated.

About This Instructable




Bio: My name is Randy and I founded the Instructables Design Studio. I'm also the author of the books 'Simple Bots,' and '62 Projects to ... More »
More by randofo:Large Motor ProjectsRemove a Wheelchair Motor BrakeBuild a Robot
Add instructable to: