E-Hopscotch, a wearable game that produces electricity (Fabricademy Final Project, FabTextiles, Fab Lab Barcelona, 2018)

In the traditional model of electricity production and consumption, energy is generated remotely, must be carried great distances to wherever it is needed and exacts a heavy toll in terms of raw materials and waste. This practice is not sustainable. With the increasing integration of electronics into clothing with e-textiles, we need to find a new way to generate the power needed for the garments of tomorrow.

E-Hopscotch is a wearable game that uses piezoelectricity for its lighting. For this project I worked on how to harvest piezoelectricity by creating a piezoeletric generator garment. A piezoelectric generator is a device that generates electricity from movement.
I designed wearable hopscotch that produces eletricity when you play with it. I thought it was a fun and magical way to charge and light my garment.

(1) DESIGN : research trends, colors & materials inspirations
(2) PATTERN MAKING : measure, cut, pin, sew
(3) ENERGY HARVESTING : test the circuit
(4) ELECTRONICS : draw the hopscotch circuit, assemble each component, solder & test
(5) E-HOPSCOTCH : final product

# Hopscotch :
- scissors, a ruler or wood sticks & a pen
- resistant and waterproof fabric (min 1500x3000 mm)
- fabric for laser cut the numbers (min 500x500 mm)
- threads & ropes (min 10 meters of each)
- 2 zippers (300mm)
- a sewing machine, bobines, sewing thread
- a measuring tape, pins, needles

# Energy Harvesting Circuit :
- a breadboard
- jumpers and crocodile clips
- a voltmeter
- an iron solder + soldering thread
- a capacitor 100uF 16V
- 4 diodes (bridge rectifier)
- a switch (you can also build your own)
- LED + resistor (if needed)
- 10 piezo ceramics (30mm diameter)
- a regulator 3V

Piezoelectric tranducers have the unique and useful property of being able to transform mechanical energy (pressure) into electrical energy, This gives piezoelectric materials a wide range of potential applications from sensors and actuators to artificial muscles.
One of the most interesting applications is in the field of energy harvesting. An electronic circuit that allows you to convert and store the mechanical energy that is typically wasted (AC current) into a source of electrical energy (DC current) that you can use for lighting a led.
Start your circuit by making a bridge rectifier by assembling 4 diodes together. The bridge rectifier or diode bridge converts the AC power input into a DC power output.
Then connect your piezo element to it (like in the diagram). Notice than the piezo doesn’t have a directionality. Thus, it doesn’tmatter in wich way you are connecting it.
Add a capacitor for storing the electricity produced by the piezo elements and and a switch to open and close your circuit.
For this first energy harvesting circuit test you don’t need to put a regulator and a battery, connect only the led and you are good to go and try it.

First, assemble all the piezo ceramics in parallel with cables cut at the perfect size to hide in the borders of the Hopscotch.
Second, connect the bridge rectifier and the capacitor and close your circuit with a small cable for making a quick test. Before soldering, test your connections and that all the piezos are working properly. Measure the rise of current, produced by each piezo ceramic, in the capacitor with a voltmeter. If everything works you can solder the piezos together, the bridge rectifier and the capacitor.
Now, you just need to add the regulator and the neon Led 3v to your circuit. The regulator allows you to correctly distribute the current stored in your capacitor. If you don’t put a regulator you are probably going to burn your led really quickly by allowing too much current to pass from the capacitor to your neon LED.

Wearables and e-textiles are slowly becoming part of our daily life but how can we pretend to be desinging sustainably when we are filling it with all of these electronics ? Is it really how we want to design our futur ? Is it possible to imagine an eco-friendly world that combines ecology, sustainability and electronics ?
During this project, I learned that is possible to harvest the energy produce by your body. I hope e-hopscotch will be the first of a long list of piezo wearable projects. I want to continue to work on finding alternatives for generating electricity, Perhaps developing bio-batteries could be my next project.

Mistakes : I don’t believe in mistakes. I believe in improvements. This first prototype only lights up, so maybe I could create a wearable that generates electricity for other devices ? The design could be also improved, using more sustainable and durable fabrics.

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