Electricity Harvesting Footwear

Did you know that you can produce electricity by just walking? Here's a documentation of my "Electricity Harvesting Footwear Insole". I have conceptualized the design over the years.


With the help of piezoelectric crystals. I was able to make a shoe that generates electricity solely by walking. 

That's easy! Or is it?

The challenge is to make a slip-on insole that can produce enough electricity to charge batteries or supply power to smart clothing. Easy as pie! Get this, I have limited myself from using dynamos (motor + gears) to generate power. Why? Dynamos are robust, noisy, cranky, and has too many moving parts, surely it will cause discomfort for the user.


Development of The Project: 

The power generating soles are one of my first concept projects. I started my first prototype five years ago. It was a very primitive, compared to my current version. My old prototype had two piezo-discs sandwiched on a TO-3 plastic spacer. It produced a fair amounts of current, enough to light up three LEDs. 5 Years later, a saw great potential so I decided to bring-up the project for major improvements.

Future Practical Applications: 

- Supply on-board/ independent power for smarts shoes and clothing.

- Aid outdoorsmen/ hikers, with GPS tracking shoes,in their journey into the vast wilderness.

- Great for areas where electricity is scarce.

- Self-powering rescue chips in shoes.




Hi! I'm Angelo, I'm 15 and live in the Philippines. I have a deep passion for learning science and technology, probably because I was born curious. I'm a well rounded tech-builder and I've been making projects at a young age of four. At the age of ten, I started publishing online write-ups (@instructables.com). Feel free to visit my site: ASCAS.tk  Over the years, I've built a numerous projects like: my homebrew-CNC-machine, FPV-drone, Quadcopter, novelty-gadgets, voice-activated android home-automation system and eco-projects. 

Everyone has an inspiration and mine is my grandpa! He was a great engineer and the best grandfather that a geek can ever have. When I was in elementary, he used to pick me up from school. Before we head home, we shop at hardware stores then build projects together at home. When he passed away, I continued my hobby in honor of him. 

When people ask me on where I get my crazy ideas, I always tell them that whenever I have a ridiculous idea in mind, I never let go of it. Even if seems impossible, a little brainstorming and tinkering would make things possible. I also tell them that I'm blessed to have friends who share a common hobby.

I also love robots! Over the years, my friends and I built tons of autonomous robots, like breakout-bots, humanoids, high-rpm line tracers, mazebots, and sumobots. I've won 1st-place in last year's nationals. This year, I am going to represent my country in the "2014 International-Robotics-Olympiad".






Questions To Ponder On:

- Does it have enough power to supply electricity for low consumption modules?

- Will it produce enough power to charge USB devices?

- Can it reach the USB standards?

- Can it power a series of LEDs?

A Larger Picture:

Coal power is the most common energy source used in the Philippines ,also in the world yet two-fifths of ouy country's population has no access to electricity. It's a big deal for people to who lives in the suburban areas to charge their phones once in a while.

Over the past years, my science experiments were mostly about renewable energy. I started my first science fair experiment when I was in third-grade, it was my first miniature model of a solar car. The receding years of my science fair entries were mostly about wind, solar, hydro and chemical energy. 

My goal is to find a new source of renewable energy, something that does not depend on wind, water or sunlight. I did some random research and I came through tons of eco-energy production articles. I told myself, if I'll go with another solar/ wind experiment, there won't be enough innovation by just remaking a project from the internet. Like all scientists, I had to think out of the box. 


The project is be accomplished by using piezoelectric materials. Piezoelectricity, also called the piezoelectric effect, is the ability of certain materials to generate an alternating current voltage when actuated.Certain ceramics, Rochelle salts, and various other solids exhibit this effect. For example, (Pb[ZrxTi1−x]O3 where,0≤x≤1), also called PZT, will generate measurable electricity when their structure is deformed by about 0.1% of the original dimension(International AAAI Conference on Social Media and Weblogs, 2012). In this project, the generated electricity on a specific time will be recorded and determine if it would be enough to completely charge a Li-ion battery or a high capacity capacitor.


History Of Piezoelectricity (wiki):

The pyroelectric effect, by which a material generates an electric potential in response to a temperature change, was studied by Carl Linnaeus and Franz Aepinus in the mid-18th century. Drawing on this knowledge, both René Just Haüy and Antoine César Becquerel posited a relationship between mechanical stress and electric charge; however, experiments by both proved inconclusive.

The first demonstration of the direct piezoelectric effect was in 1880 by the brothers Pierre Curie and Jacques Curie. They combined their knowledge of pyroelectricity with their understanding of the underlying crystal structures that gave rise to pyroelectricity to predict crystal behavior, and demonstrated the effect using crystals of tourmaline, quartz,topaz, cane sugar, and Rochelle salt (sodium potassium tartrate tetrahydrate). Quartz and Rochelle salt exhibited the most piezoelectricity.

A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)

The Curies, however, did not predict the converse piezoelectric effect. The converse effect was mathematically deduced from fundamental thermodynamic principles by Gabriel Lippmann in 1881. The Curies immediately confirmed the existence of the converse effect, and went on to obtain quantitative proof of the complete reversibility of electro-elasto-mechanical deformations in piezoelectric crystals.

For the next few decades, piezoelectricity remained something of a laboratory curiosity. More work was done to explore and define the crystal structures that exhibited piezoelectricity. This culminated in 1910 with the publication of Woldemar Voigt's Lehrbuch der Kristallphysik (Textbook on Crystal Physics), which described the 20 natural crystal classes capable of piezoelectricity, and rigorously defined the piezoelectric constants using tensor analysis.



 Gathering The Parts & Materials:

Parts/ Materials: Tools & Equipment:
- Generic USB Powerbank
- Piezoelectric Transducers (6x)
- 1N4007 Rectifier Diodes (4x)
- Hookup Wire (12" long)
- Old Pair Of Shoes
- Contact Adhesive

- Digital Multimeter
- Multitool (w/ pliers)
- Rotary Tool


Measuring The Size Of My Sole:


I acquired the size and shape of my shoe's insole then got a pair of heavy-duty shears/ snips then carefully cut the PVC material. The plate acted as the primary mount of my piezoelectric discs. The plastic material should have at least 2-4mm of thickness. Too thick then the elements could shatter, too thin and it would barely flex.

Draw Circular Guidelines For The Holes:


I surrounded the PVC plate with three piezo discs. I grabbed a pencil and traced the piezo discs after getting a fixed preview of my setup. Afterwards I drew smaller circles inside the larger ones. 

Grinding Holes On PVC Pads:


I grabbed my rotary tool and started to grind holes, using my markings as a reference. 

Glue The Piezoelectric Discs In Place:



These piezo discs must endure a lot of flexing since I will be stepping on them repeatedly!

Soldering The Piezoelectric Discs In Parallel:


Building A Bridge Diode:


Piezoelectric elements produce AC when subjected to mechanical stress. I needed a DC voltage to charge some batteries and capacitors, adding a bridge diode was the solution to my simple problem. CFL bulbs contain electronic ballasts. I was able to recycle eight 1N4007 rectifier diodes from my box of busted CFLs.

Adding Foam Pushers:


I my design required a soft block of foam to push each pair of piezo discs inward. 

Observation And Testing:

Start by getting a digital-tester and switch it to the 2 digit DC range. Piezo elements produce a short burst of current, the moment you push them, so adding a 100nF capacitor should make the readings slower and much more readable. (Skip to result-page to see the much detailed readings)

Installment Of The Insole Generator:

A Temporary Test:


This was the first test that I ran on the insole generator.  In the picture, my insole generator is soldered directly to my powerbank's lithium battery. The insole generator peaked at 28 volts. The current may be small, but the voltage is enough to damage the powebank's 5v charger-inverter (module). I won't be using the 7805 regulator IC since it is old and inefficient.


The second test went through a charge collection circuit which I acquired from the all famous "solar engine" (aka FLED). The motor was replaced with my powerbank's 5v feed while the solar panel was replaced with my insole generator. 


The test was conducted by draining the powerbank to it's safe zone (auto-cutoff). Basketball is my daily exercise and my bonding time with my dad. I played two straight hours with my insole generators on-board. 

Future Prototypes: 


- More piezoelectric discs to cover a wider surface area

- Designated bridge diode per piezo pair





Version 1.0 (Current Version):

How The Readings Were Acquired:

An Arduino development board was used to establish a simple oscillocope setup. It was plugged to the computer, the built-in TTL was used to establish serial communication between the Arduino and PC. A sketch was uploaded, using the Arduino IDE, to monitor the Analog pin where the insole generator was connected. A separate program, called "processing 2.0", was used to monitor the ripple given off by the converted AC►DC output of the generator.  



The Averaged Readings:
Pressing By Hand = 15.03 volts (2mA)
Walking By Foot = 18.53 volts (5mA)
Running By Foot = 27.89 volts (11mA)

Version 2.0 (not covered by my GSF entry):

My second version was equipped with 2 pairs of 35mm piezo discs rather than smaller 25mm version. It yielded a lower voltage but resulted to a higher current. I was suspecting that the 35mm piezo disc's thickness played a huge role on the major voltage loss so I pulled off my digital vernier caliper. I, then found out that the 35mm piezo disc was twice thicker than the 25mm. Each measured (0.6152mm) and (0.3210mm) correspondingly.


The current results showed that the product has potential to charge lithium batteries. Though there are room for improvements, it showed positive signs for it to be further developed.  


Based from the results, the insole generator has enough power to supply voltage for low powered circuits such as MCUs (Micro Controller Units - ex. ATtiny) and TTL Bluetooth transmitters. I can now say that the product is ready for production and is highly usable for smart clothing/ shoes although charging USB devices won't suffice just yet. 

Further Plans:

If a whole insole was to be made with a thin flexible sheet of metal and glazed with piezoelectric elements (back-to-back) then it would probably produce enough power to qualify within the USB standards. 


A standardized opensource 3D printed design will certainly introduce a new energy-production concept to the DIY community. When everyone has access to an opensource project great ideas flourish! 






To The Instructable Community:

I may not be good in English but I would like to express my deepest gratitude for your generous support. I would like you all to know that if it wasn't for the advice and constructive criticism, I would not even have pulled this project. Thank you guys! You always give me the spirit to make new projects.

 Reading Materials Owned By Yours Truly:  




Other References:






Radioshack Learning Lab Kit/ Books