Yoga Mat

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Yoga Mat

Though the title may seem very awkward, the result is an awesome and innovative device. So, let's start. This Yoga Mat, as it is called for now, is nothing but a platform or surface under which some small discs, specifically called - Piezoelectric Transducers are fitted. When a person runs, walks, jumps or does yoga, the discs generate a considerable amount of electricity which can be stored and used to power an appliance (LED, motor etc.).

I got inspired by some similar Instructables on piezoelectricity generation and just cooked up a new application of the concept. I have used this thing for various exhibitions and have been successful in impressing everyone. I hope that this tiny contribution from my side will help solve the looming global energy crisis.

Theory and Prerequisite Knowledge

PIEZOELECTRICITY

Piezoelectricity is the electric charge that accumulates in certain solid materials in response to applied mechanical stress.The word piezoelectricity means electricity resulting from pressure. It is derived from the Greek piezein, which means to squeeze or press, and electron, which means amber, an ancient source of electric charge. Piezoelectricity was discovered in 1880 by French physicists Jacques and Pierre Curie.

EFFECT OF SERIAL AND PARALLEL COMBINATIONS ON PIEZOELECTRIC CRYSTALS

After doing a lot of research and experiment, I have come to know that when the crystals are connected in series and an even amount of pressure is not received by all of them, they tend to cancel out each other's output. So, to avoid that situation, we have to connect the crystals in parallel to each other.

SOLDERING SKILLS

You need to have some really good soldering skills. This is because of the reason that if you hold on too long when you will be soldering the crystals, the ceramic may melt. Thus, damaging the crystal.

Materials Required

You can find these things in your home easily or you can also purchase these online or from an electrical hardware shop.

For the circuit,

Piezoelectric Crystals (20) - You can find these in buzzers. I have used 20mm piezoelectric crystals in my project. In India, they cost about Rs 10-16 each.
1N4007 Rectifier Diodes (4) - You can find these almost in every PCB. These are the small black diodes with a grey marking on one side.
Electrolytic Capacitor (120uF/400V) - I got mine from a faulty laptop power adapter, but you can find these at stores. We require only ONE capacitor.
Switch - It would be better if it is a SPDT switch.
Soldering Iron and Solder
Connecting Wires
Multi-meter for testing
LED (3V)

For the surface,

Cardboard (2) - I used the dimensions 1m x 1m for 20 crystals.
Buttons (20) - To focus the pressure on the crystal
Tape and Glue

That's all you need !! Believe me !!

Making the Circuit

We have to follow the given circuit diagram.

First of all, solder a pair of wires on both the areas of the piezo. That is, solder one on the gray area and another on the shiny silver or golden area. As we know, we have to connect the piezos in parallel. So, connect all the wires coming from the base (shiny) part of the piezo to be careful. If required, you can fix a copper board on either sides of the cardboard and connect all the wires from the base of piezo to that copper board. They will be connected to each other.

Now, take the wires from the top part of the piezo and connect them. You can also connect them on the second copper board if you want to be more organised.

Then, connect a piece of wire to one copper board and the another piece of wire to the other board. The polarity has nothing to do here as the crystals will produce AC current. Fix them as mentioned in the next step.

Next, make a rectifier bridge using the 1N4007 diodes. The gray portion is the negative end of the diode. So arrange them as shown in the picture and solder them. Connect the two wires (shown as green wires in the figure) as shown.

Connect two wires (one is shown as red +ve DC and the other blue -ve DC).

Next, identify the poles of the electrolytic capacitor. Usually, the negative pole is clearly marked. Connect the blue wire from the rectifier to the negative pole of the capacitor. Connect the red wire to one terminal of the switch. Connect the other terminal of switch to the positive pole of the capacitor. Keep a multi-meter ready to test the connections and measure the test voltage.

Making the Surface

Take a cardboard and fix the crystals and copper boards as shown. You can ignore the small diodes, they are removed as they serve no useful purpose to my model (sarcastic here).

It is better to make small cardboard pads and fix them on the base cardboard. Then fix the crystals on them. To focus the pressure applied to the crystal, attach a button at the centre of each piezo crystal with a tape.

Cover this cardboard containing the crystals with another cardboard to cover them.

Housing the Other Components

You can take a small plastic box and fix the bridge diode, capacitor and switch in the box.

Connect two wires with the poles of the capacitor and solder crocodile / alligator clips on the ends. This is very useful and required part for testing.

Fix everything and be ready for testing.

Testing and Observation

Piezoelectric Crystals : A Energy Source

Connect the clips to the multi-meter and turn on the switch. Now walk on the surface you just made.

In my case, I was able to get 3V in 5-10 seconds and then it is slow and 10V takes a minute.

When a LED is connected to the capacitor, it glows brightly for a couple of seconds. For this, the capacitor has to be charged to slightly above 3V.

If you connect a small motor and charge the capacitor to 20V, it runs very smoothly for a few seconds.

After every application, the capacitor gets discharged and it has to be charged again.

The video embedded here shows a glimpse of this process.

Result and Sources of Error

The device thus made is an innovative method to harness the energy spent in doing mechanical work to electricity. This concept is already used in some sidewalks in China. It is a field where a little research has been done in comparison to other fields.

There should be proper insulation to prevent short circuit. The switch should be turned off as soon as capacitor gets charged. Otherwise, it will get discharged.

An step-up transformer or DC to DC converter can be used to power something at a greater voltage.

Hurray!! You have made a Yoga Mat that generates electricity... I'm looking at a modification where we can charge our mobile phone while doing Yoga... Stay tuned...!!