Introduction: Piezoelectric Shoes: Charge Your Mobile Device by Walking!

NOTE: This is my first instructable!

Have you ever had that moment when you had a very important text to send, but before you could finish sending it, your phone died? Pretty much any person with a mobile phone/device has experienced that frustrating moment when a device fails to complete its task due to a lack of energy. My project is designed to fix this problem in a way that promotes health by creating a shoe insole that converts the physical energy created by walking into electricity, which is then stored in a portable battery pack. This way, you will always have an emergency power source (and you will be renewing some of your own physical energy too)!

Step 1: PARTS AND TOOLS

The following lists are divided into 2 categories. The first category consists of things you NEED to complete the project, while the other list consists of things that are very HELPFUL.

Things that you NEED:

  1. Shoes (duh!)
  2. Piezo electric elements (x14) I found 15 of them for 15.99 here
  3. Rechargeable battery pack w/ charger(x1) I got mine from 5 and Below for 5$
  4. Hot glue gun w/ hot glue
  5. Soldering iron + solder
  6. Foam/cardboard/anything you can squish (I used foamboard that I got for 1$)
  7. Access to a 3D printer (If you do not have access to a 3D printer, you can always always substitute a different material/plastic, but my instructions will be based off the 3D printed design
  8. 1n4001 - 1N4007 Diodes (x4) OR a CFL lightbulb, which I will show you how to take apart in order to salvage diodes needed for this project.

Things that are HELPFUL:

  1. Dremel tool
  2. Helping hands
  3. Velcro strips (HIGHLY RECOMMENDED!)
  4. Multimeter
  5. heat gun (if taking apart CFL bulb)
  6. ruler/caliper

Step 2: HOW DOES IT WORK?!

NOTE: If you do not like learning about really cool stuff, you can skip this step.

In order to fully appreciate the science behind this project, it is helpful to understand how it works. Essentially, the main power source that makes this project possible is something called a piezoelectric transducer (I know, its a mouthful). Piezo electric transducers, or piezo elements, are comprised of materials such as crystals and certain ceramics that have a special property which allows them to convert physical energy into AC electricity. Fortunately, we can take advantage of this special property by putting piezo elements underneath our feet in such a way that every time we take a step, we are using our weight to push on the piezo electric elements- which then in turn convert that energy into electricity. The only issue with this, however is that we need DC, not AC in order to power our stuff. We can solve this problem by creating a bridge rectifier with diodes to convert the AC power to DC power we can use.

Step 3: MEASURING YOUR SHOE AND PRINTING THE FILES

In order to make our piezoelectric generator, we are going to need a plastic base. I have provided the links to my tinkercad files below. Feel free to customize them to suit your needs/foot measurements. The piezo element holes are strategically placed so that they line up with the large indents on my shoe's insole, which indicate the areas of most pressure. These files are based off of my foot, which is a size US 9.5 . Although my heel piece fit perfectly, my toe piece required a good bit of sanding in order to get it to fit properly.

piezoelectric shoe insole (toes)

piezoelectric shoe insole (heel)

Step 4: GLUING THE PIEZO ELEMENTS

Once we have finished creating the base for our piezoelectric generator, its time to hot glue them on. I found that the best technique to glue the elements to the board was to apply a thin layer of glue around the edge of the hole in the plastic, then quickly pressing the piezo element onto the glue before it cools. Be careful not to apply too much glue, or else you may restrict the foam pads (which will be glued on top of the piezo elements) from fully compressing. Also, make sure the glue does not cover the contact points of the black or red wires, because we will be soldering to these points soon. Make sure you glue piezo elements on both sides of the plastic. If you have a multimeter, you can ensure that your piezo elements work by setting the multimeter to AC volts and pressing on the piezo. After you have glued all of the piezo in their appropriate spots, you can then glue the foam/cardboard pieces onto each piezo element.

Step 5: SOLDERING THE PIEZO ELEMENTS TOGETHER

Although piezo elements generate plenty of voltage, they do not generate many amps. We can solve this issue by wiring the all the piezo elements in parallel (in other words, the positives are always soldered to each other and the negatives are always soldered to each other). In this way, we will be able to increase the amount of amps and consequently charge our devices faster. In order to prevent wires from braking off of the solder joints, use hot glue to fasten part of the wire in place so that the stress on the wires is not enacted upon the solder joint. You can connect the piezo elements from one side of the plastic to the other by threading the wires of one of the piezo elements through the holes so that they can be soldered in parallel to a piezo on the other side. Once all of the piezo elements on the heel piece are wired in parallel, solder the last piezo in the chain to one of the piezo elements on the toe piece, and continue to solder the piezos in parallel until all 14 elements are connected.

Step 6: TAKING APART CFL BULB FOR PARTS

NOTE: If you already have your diodes, you can skip this step!

If you are like me in that you do not have diodes lying around, have no fear! You can find perfectly good diodes inside of your old, broken CFL bulbs in your house. Here is how you do it:

CAUTION: CFL BULBS CONTAIN MERCURY AND OTHER POISONOUS MATERIALS WITHIN THEIR GLASS TUBES. DO NOT BREAK THESE TUBES!

  1. Go outside with a screwdriver or some sort of tool capable of prying things apart, and sit in the grass or some other soft material. By doing this, you can significantly lower your chances of braking the glass tube, which contains poisonous substances that you don't want to mess with.
  2. Locate the seam by which the two plastic halves of the CFL bulb are connected, and begin to carefully pry the two pieces apart with your screwdriver.
  3. Once the bulb has split apart, you will notice that the PCB inside is being held back by two wires connected to the lightbulb's metal base. You can either cut these off like a civilized person or do what I did, which was to continually pull until the wires broke off.
  4. Most likely, your CFL bulb will contain 6-8 round, black diodes with gray stripes on them to indicate their positive ends. However, if you are like me, your diodes are rectangular prisms, not round, and have engravings on one end to mark the positive side.
  5. Once you have located the diodes, you can take them off by heating up the solder with your soldering iron and pulling the diodes away. If you have a heat gun, you can take the diode off much easier by applying heat all around the diode so both sides of the diode can be pulled away at the same time. Remember, you only need to get 4 of the diodes in order to create our AC to DC converter.

Step 7: BUILDING/WIRING THE BRIDGE RECTIFIER

BUILDING THE BRIDGE RECTIFIER:

Ok, so for those of you who do not know how to read a circuit diagram, those 4 line segments with arrows on them represent diodes. The arrows always point to the side of the diode that is marked, also known as the positive side. If you have small, rectangular diodes like me, the positve sides are not marked by coloration, but rather small, engraved lines/notches. By following this diagram, you should be able to create the bridge diode.

WIRING THE BRIDGE RECTIFIER:

  1. Wire the piezo element wires to the bridge diode according to the circuit diagram. Since the current is AC, the position of the wires are interchangeable, as long as they connect to the correct diodes in the diagram.
  2. Strip the usb charge cable that came with your battery pack to reveal the internal wires.
  3. For the purpose of this project, we will only need the red and black wires, so strip those as well.
  4. Twist the frayed wire strands of each wire, and tin them with solder
  5. Solder the wires to the bridge diode accordingly. Be sure to check polarity since DC voltage has positive and negative terminals.
  6. Hot glue the connections to prevent the wires from breaking off.

Step 8: INSTALLATION AND FINISHING TOUCHES

Once we have finished wiring the piezoelectric generator, we are ready to install it! All you need to do is slip the plastic piezoelectric generator inside of your shoe, then insert the original sole on top of it. Take the USB cable wired previously and thread it between tongue and the outside of your shoe as shown in the pictures above. In order to mount the battery, stick it between the tongue of the shoe and the laces and tie your shoes tightly. If you have velcro, I would recommend using it to better fasten the battery pack to prevent it from falling out while running. I would also recommend making a foam cutout of your other shoe's sole so you can use it as a riser in your shoe with no generator in it. I used my shoe that did not have a piezoelectric generator in it as a storage for my mobile device's charge cable, so I will always have everything I need for charging.

Step 9: EXERCISE!

Now that you have finished your electricity generating shoes, there is only one way to see how well they work- EXERCISE! By taking a walk, hiking, or playing a sport for several hours, you should be a able to conduct enough electricity to charge your mobile device. Keep in mind that your battery only charges when ever you take a step, so it should take a while to get a good charge on your battery.

Comments

author
raj dagli (author)2017-07-21

only 1 question will it be able to charge a 1500mah powerbank? and if yes plz if anyone knowns how much time?.. i need help plz

author
SaffriM (author)2017-04-27

Does not work somehow. Did it exactly as instructed. The whole circuit itself does not able to charge a 5V input powerbank and a smartphone.

author
Palwasha Aslam (author)2017-04-10

Appreciable ... I am working on same project, but instead of piezoelectric shoes , i am working on piezoelectric array.As piezoelectric are generator, so my question is how can we connect generators in parallel? .They don't generate same voltage at same time,so on pressing,the one with less voltages will start working as load to other generating high voltages, and we know the inverse piezoelectric effect too. so we will be facing loss of voltages. Any Solution ?

author
PabitraD (author)Palwasha Aslam2017-04-20

Heyy... I am also working on tbe same project and vibration energy harvesting from piezo.. I will be making this shoe ready in few days.. For the problem you mentioned, you can use diodes for every piezo in order to get a steady and enhanced response.. But it will dissipate more energy due to its biasing need.. Using piezo array will also do..but it depends how have you connected the piezo sensors.. All the best for your project.. You can discuss related topics on piezo on pabitra1991das@gmail.com

author
DIY Hacks and How Tos (author)2016-05-25

Cool invention. Do you have any data on how much power you are actually generating.

author

When walking, it generates an average of 5-6 volts, but maxes out at around 9 volts. As for the amperage, each step generates about 10 milliamps of current.

author

at 10 milliamps constant it will take 200 hours to charge a 2 ah phone battery

so there's that

author

you mean 200 steps I think

author
TiffinyS (author)MoMo mahdy2017-03-27

Assuming that a single step is able to sustain a 10mA current flow for an entire second, it is closer to 3 hours. That is, if you can run 200 steps in 1 second, you will generate 2 amp seconds. More realistically, you will run (or walk) at 1 step per second, generating 10mA/s which is 600mA/min (or 0.6 Amp Minutes), which means in an hour, you generate 0.6 Amp hours... if your phone has a 1.8Ah battery, you will need to run/walk/jog on the spot, for 3 hours (or 10800 steps).

NOTE: This is assuming that 1 step generates enough power to sustain 10mA for an entire second... I expect that it will not however, and your average current over a 1 second period will be closer to 0.1mA (or less) which then scales your steps up by a linear amount.

author
Ethan Rislov (author)2017-02-23

I have don the same thing for my science fair project and all I did was used about 10 piezoes and a capacitor pack a switch 5v regulator and the female end of a USB and it works perfectly

author
JamesC_1700 (author)2016-06-07

was it really able to charge your battery pack? Were the voltage and current enough? I'm trying to do the same project but I can't charge my powerbank with a 5v, 1a requirement. My piezosystem produces an average of 12volts. The piezosystem is made of 6 piezos in parallel. I tried connecting it to an L7805 ic to get 5v and 1a current but to no avail. Still doesn't work. Really Need help for a school project. A reply asap will be much appreciated

author
Theborat (author)JamesC_17002017-02-17

Hey, even I'm planning to do this as my college project. But your comment worries me. Does the phone or the battery pack get charged at all? Or does it not produce enough current for the device to register it? I'm concerned that if i go along with this project and it doesnt produce any current I'll myself in a fix. So if you could help me out by sharing whether you managed to make it work, I'll be really greatful. Thank you

author
JamesC_1700 (author)Theborat2017-02-17

Wasn't able to make it work. I'm sorry but I know there is an available piezoharvester module i found on youtube. Its a small circuit that regulates piezo electricity to bearable voltage and currents.

author
minj5 (author)2017-02-14

Step 7 was really confusing for me... Can anyone explain to me exactly what to do? I don't do this type of projects often.

author
Awesometushar (author)2016-10-31

I used 6 pezios and they are generating only 1-3 volts... please help me pleaseeee fastt

author
RajeshK207 (author)Awesometushar2017-02-10

And how much Amp per step press?

author
SoumitaC2 (author)2017-01-02

I'm using 20mm piezo plates. Do they have lesser voltage generating capacities than 27mm ones?

Also, I tried lighting an L.E.D from the plates, they did light but only for one brief moment, like blinks. Is it possible to make them glow brighter a bit longer?

author
ThejasG (author)2016-12-22

or its better to charge the power bank such things with regulator output,then use that power bank output to charge the mobile.Due to fluctuations of voltage it may damage your mobile by directly connecting the FPG circuit output.

author
ThejasG (author)2016-12-22

use a 5 volt regulator after the rectifier circuit regulator mentioned to be IC7805.

author
NiharL made it! (author)2016-12-05

hey, i have made it and it gives around 15- 20 volts on per press, but what should i do to make it charge the phone. is your phone charging if possible pls upload a video .

20161206_122611.jpg20161206_122617.jpg20161206_122628.jpg
author
ManuelA11 (author)2016-10-18

great project you have there

anyway .. what brand and type is your rechargeable battery pack..?

author
rewakhir (author)2016-08-31

Amazing Project.... but please can u help me ! I want to know the Specifications of the piezo elements.... and how can i get piezo elements?

author
rewakhir (author)2016-08-29

Amazing Project.... but please can u help me ! I want to know the Specifications of the piezo elements.... and how can i get piezo elements?

author
Awesometushar (author)2016-06-17

Hey bro please help me! How much voltage is produced by it and isnt the overvoltage harmful for a phone battery? How to manage the voltage output?

author

My piezos generate around 5-9 volts, but I have seen some piezos that generate much more electricity than that. If over voltage was to happen, it would NOT hurt the phone battery because you are recharging a battery pack, which will then charge your phone battery with the recommended voltage and amperage. Worst case scenario, you could potentially damage your portable battery pack, which (if you buy the same batteries I do) only costs 5 dollars.

author

Can i use a 5v step down regulator??

author
CraftAndu (author)2016-07-18

Great for Fb and Instagram junkies :)

author
ImanuelEzra82 (author)2016-06-26

Amazing Project,Loved and Voted!

author
Zach Alfaro (author)2016-06-06

You got my vote Abel. Go Abel!!! WOOOOO!!!!

RED ROBSTER......

author
Zachalfaro (author)Zach Alfaro2016-06-20

Indeed Red Robster

author
Zach Alfaro (author)Zachalfaro2016-06-20

indeed kind sir

author
Awesometushar (author)2016-06-17

Hey can i use a 5v regulator to control voltage??

author
Diego21ARG (author)2016-06-13

I have a doubt... Aren't piezoelectric suppossed to generate DC current??

author
Abel Haynes (author)Diego21ARG2016-06-13

Piezoelectric elements generate AC, not DC. If you wire a piezo up to a multimeter, you can actually see the current pulsating.

author
Modern Da Vinci (author)2016-06-12

Hi there! I'm Kyle, and I'm an amateur inventor. I really admire your work here and I can't wait to make it. I recently bought a 3D printer and I'm still learning how to use it. Is there anyway you can explain to me how I can size the prints to fit my size? Or is it not too much of a difference if I wear size 10?

author

It is probably not too much of a difference since I wear a size 9.5, and my piece required sanding to fit in my shoe. If you think that you need to adjust the sizing, you can do 1 of 2 things:

1) Make a tinkercad account and edit my files to make them fit your shoe size. Make sure you press the ungroup button at the top before you change the size of the piece so that the piezo holes stay the same size. When you have finished adjusting the file to fit the size of your shoe, hold down shift and click all the things you want to combine again and click the group button.

2) If you want to you can use this shoe insole generator, courtesy of gyrobot. I found it to be rather complicated, but i'm sure if you took the time to figure it out you could create an insole much more exact than mine. Then you could upload it to tinkercad and cut out piezo holes wherever you felt was appropriate.

author
JamesC_1700 (author)2016-06-07

I've tried directly wiring the rectified piezosystem to a rechargeable battery pack, and damn it broke my batteries. For the battery pack, I made it myself. I got two 3.7v phone batteries connected in series. How do you not destroy your batteries and charge them?

author
Abel Haynes (author)JamesC_17002016-06-13

Did you use a protection circuit when charging your batteries? I would recommend using a premade battery pack with a built in protection circuit, which will regulate the power going to the battery and therefore prevent battery damage. My battery pack charges, but it does so very slowly. Keep in mind that the piezo elements not only produce an extremely low amount of current, but they only produce that small amount of current each time you take a step.

author
bugcarrie (author)2016-05-27

Too Great! I'll buy one!

author
Zach Alfaro (author)bugcarrie2016-06-06

Me too bugcarrie

author
gymnastics123 (author)2016-05-30

Does it come in pink? Pink is bae.

author
supertux123 (author)2016-05-27

omg needs a helmet

author
bhavik zure (author)2016-05-26

coool idea,

n surely deserve my vote.

author
Abel Haynes (author)bhavik zure2016-05-27

Thank you for your support!

author
Adasha (author)2016-05-27

Hello Shark Tank!!!

author
ChelseaM16 (author)2016-05-25

Can I suggest that a simple BMS (battery management system) and USB-out charger are connected along with a small battery? (cheap mobile phone battery for instance)

This would allow you to charge the battery pack, then charge your phone from that later. the circuit boards are worth cents and are very small, the battery can be any size and also very slim.

author
Abel Haynes (author)ChelseaM162016-05-26

I used a 5 dollar rechargeable battery pack designed to recharge mobile devices, which has a protection circuit built in (it is the black thing on my shoe in the introduction picture).For the charge cable, I decided to leave the usb out port open in case I buy a different phone or want to charge something other than my phone. The battery pack is fastened by Velcro and held in place by my shoelaces, so can I take it off to charge my phone whenever I want.

author
Abel Haynes (author)Abel Haynes2016-05-26

*I can

author
MAMBOM (author)2016-05-26

SO incredible idea!

author
Abel Haynes (author)MAMBOM2016-05-26

Thank you! Don't forget to vote for my project if you feel it is worthy, I'd really appreciate it!

About This Instructable

35,014views

116favorites

License:

Bio: Hey guys! My name is Abel Haynes and I am a highschool student with a passion for making cool stuff!
More by Abel Haynes:Piezoelectric Shoes: Charge Your Mobile Device By Walking!
Add instructable to: