Electricity Generating Footwear - Generate Electricity By Walking

Did you know that you can produce electricity by just walking? Here's a little science experiment that will show you a little trick on making insoles that can charge USB devices! The challenge is to make a slip-on insole that can produce enough electricity to charge batteries/ USB devices. 

Concept Behind The Project:

Piezoelectricity was present ever since mid-18th century. Piezoelectricity is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics in response to applied mechanical stress. This sounds familiar! Yes they do, you can actually find those piezo elements in your old/ outdated earphones from the 90's. 

NOW THE FINAL STEPS TO MAKE IT :

Parts/ Materials:
- Cheap/ Generic USB Power-bank
- Piezoelectric Transducers (6x)
- 1N4007 Rectifier Diodes (4x)
- Hookup Wire (at least 12")
- Old Pair Of Shoes
- Contact Adhesive

Optional: 
- 100nF Mylar Capacitor (for testing)
- Hoop & Loop Fastener (Velcro)
- LED Indicators (for testing)
- Superglue (for fixing wires)
- Smartphone Sport Strap
- 5v Switching Regulator (w/ super-cap)

STEP 1 : MAKE YOUR SOLE



Get the size and shape of your shoe's insole then get a pair of heavy-duty shears/ snips and carefully cut the PVC material. The plate will act as the primary mount of the piezoelectric discs/ elements.

Remember: Thickness matter, you need at least 2-5 mm. If your material is too thick, the piezo elements will break due to too much flexing. If your material is too thin, the piezo element won't bend at all thus converting less power.

Step 2: Find And Cut An Ideal Material (Sheet/ Plate)

Now surround the PVC plate with three piezo discs. How do I know where the center is? The "center" that I'm referring to is area where all the pressure is withdrawn by your foot, your sole.

After getting a fix preview of the setup, get a pencil and trace the piezo discs. Finally use your compass to draw smaller circles, about 
2 mm smaller in radius. The 2 mm spacing will act as your margin.

What material should I use?
Based on my design, I needed a plate that is 2-5 mm thick, lightweight, stiff and can endure a lot of flexing. Metals are too stiff while carbon fiber is too thin. After playing around with a bunch of materials, I've found out that PVC fits best in my application.

Were did you get the PVC material? 
PVC materials are all around us. You can find them in your local hardware store but in the form of pipes. I got mine from our excess supply of PVC pipes when our house was built.

Step 3: Grinding Holes On PVC Pads

In this step, grinding is required to bore/ drill round holes. Since I don't have large drill bits (as large as the marked area), I've thought of way to cleanly cut the holes and that's by using my handy rotary tool. 

If you don't have a rotary tool, you can still cleanly cut the plastic by doing it "the old fashioned way", by heating an iron nail and melting the plastic.

Step 4 : Gluing The Piezoelectric Elements.

These piezo discs must endure a lot of flexing since you'll be stepping on them repeatedly! Never use superglue, if you do, the moment you step on your insole the piezo discs will snap off the PVC pad. Instead, use those quick setting "contact adhesives". Their rubbery characteristic makes them ideal for this project since they stretch whenever they are bent.

Step 5 : Soldering The Piezos Together

Solder all piezo elements together in parallel. Don't solder them in series because you'll need more current than voltage and those piezoelectric discs will cancel each other's power output when not actuated at the same time.


Piezo elements produce AC currents. Unlike DC currents, you can't just tap in the line. since AC currents are always alternating polarities. Just like power generators, whether it may be solar or petrol, you can't just tap directly to the power-lines without aligning the AC wave's phase otherwise the generator will cancel each other. (Ex. Negative meets Positive - Positive meets Negative). This infers that parallel works best for our project. 

Step 5 :Soldering The Piezos Together

CIRCUIT CONNECTIONS

Step 6 : Adding Foams Pushers

 Now glue small a small piece of foam on the very center of each piezo disc. These foams will act as pushers. These foams will squeeze the piezo discs inwards (like sand witches) while walking.

Step 7 : Observation And Testing

Finally, we are going to test the validity of or theory. Start by getting a digital-tester and switch it to the 2 digit DC range. Remember, piezo elements produce a short burst of current the moment you push them so adding a 100 NF capacitor should make the readings much more readable.


My volt meter displayed:
Pressing By Hand = 15.03 volts (2 mA)
Walking By Foot = 18.53 volts (5 mA)
Running By Foot = 27.89 volts (11 mA)

Step 7 : Installing The Insole

Step 8 : Adding A Powerbank + Soldering

SOLDER THE WIRES TO THE BATTERY

                                                            AND ITS MADE

              

   For any query mail to sciencebuddy98@gmail.com

   And don't forget to comment....

    

  VIKAS