Piezo Electric Effect Demo

For the course Design Engineering for Fysici (DEF) we were tasked to make a demonstration that would show a Physical phenomenon about energy conversion from one form of energy into another. This would be done for Physics teachers at high school to show their students how a certain Physics phenomenon works. All of this needed to be made with a budget of 70 euros.

For this project we chose to demonstrate the Piezo electric effect. In short, a Piezo crystal will generate voltage, when a mechanical pressure is applied.

To demonstrate this, we needed to make Piezo crystals and eventually a setup that would show this energy conversion.

Piezo Crystal synthesis

1. Cream of Tartar
2. 200 gram
3. Bought from a apothecary in Delft called "de salamander"
4. Baking Soda
5. 500 gram
6. https://www.ah.nl/producten/product/wi386329/arm-en-hammer-pure-baking-soda
7. Demiwater
8. 1 Liter
9. https://www.ah.nl/producten/product/wi460934/ah-gedemineraliseerd-water
10. Filter
11. For example we used generic Coffee filters
12. Oven
13. Needs to be able to heat from 65 degrees until 230 degrees celcius
14. Beaker
15. Needs to be able to hold at least 500 grams and has to be heat resistant
16. Sauce pan
17. Scale
18. Glass stirring rod
19. Baking dish
20. Insulated box
21. We made one ourselves, using a cardboard box, aluminium and foam
22. Tupperware
23. Tweezers
24. Refrigerator

Set up

1. Aluminium extrusion (1 x 40 cm, 4 x 30 cm and 1 x 20 cm)
2. 22 bolts (M10,10) and 21 T-slot nuts for the extrusion
3. 9 Angle brackets and 2 straight brackets for connecting the extrusion
4. A bolt (M4,20) and nut (M4)
5. Allen wranch
6. Plexiglass tube
7. 0.05 by 0.3 meters
8. Wooden holder (laser cut from 3mm mdf)
9. 0.35 by 0.28 meters
10. 20g of pla filament (and access to a 3d printer)
11. 32 x 8 MAX7219 Module LED Matrix
12. Breadboard
13. Some wire and resistors (10 MOhm)
14. Arduino Uno
15. Voltage source (9V battery, laptop, socket)
16. Drill (Drillbit sizes 5 mm and 6 mm)
17. Tupperware (10 by 10 cm)
18. Foam and felt

There are various different substances with piezo electric properties, however, for our purposes rochelle salt is the best option as it can be made using readily available materials. We mainly followed a recipe by rimstar How to make Rochelle salt piezoelectric crystal.

The first step is creating washing soda (sodium carbonate) from the baking soda (sodium bicarbonate). To do so the baking soda must be spread thin on baking trays and heated in an oven according to the following steps.

1. one hour at 65 degrees celcius
2. one hour at 120 degrees celcius
3. one hour at 175 degrees celcius
4. one hour at 230 degrees celcius

(these times and temperatures were from the rimstars recipe)

You now have washing soda and cream of tartar.

Fill a pan with around 4 cm of water and start heating it on the stove, make sure to keep it lightly boiling. Also be sure to thoroughly clean the beaker and rinse with a bit of distilled water to remove any mineral buildup.

Underneath are the next steps summerazide.

1. Fill a beaker with 250 mL of distilled water and add in the cream of tartar, stir until in suspension and put the beaker in your saucepan to heat. This looks like a creamy white mixture adjacent to milk.
2. Slowly start adding the washing soda to the beaker, we used teaspoon increments because the mixture will bubble up too much if you add a lot of washing soda at the same time.
3. Thoroughly stir the mixture in between steps.
4. After a while you will start to notice the solution becoming clearer. Keep adding the washing soda untill the mixture no longer fizzes when new soda is added.
5. The solution is now done, you have created a supersaturated solution of rochelle salt (if everything went well :) )
6. Filter the solution through a coffee filter into a clean beaker. Feel free to repeat using clean beakers and new filters each time.
7. Add the solution into the container it will be stored in. We opted for a insulated box with a plastic container inside to gradually cool the solution down over time. After 6 days we moved the solution to a fridge. The crystals will take up to 2 weeks to fully form.

In the pictures above a process of the evolution of the synthesis of the piezo crystals is added.

To begin step 2, all the necessary items were gathered. In our case we needed 4 item profiles of 30 cm, 1 item profile of 40 cm, 1 item profile of 20 cm, 22 bolts, 21 T-slot nuts, 9 angle brackets and 2 straight brackets.

When all the items are gathered one can start by assembling the bottom square, from now on called the base. This can be done by using 4 angle brackets, 8 bolts and 4 pieces of extrusion of 30 cm. First place the T-slot nuts in the holes on the side of the pieces of extrusion. It is important to make sure that the T-slot nuts are proparly inserted into the slots, otherwise you cannot properly attach the piece of extrusion to each other with the screws. To tighten the pieces of extrusion firmly, it is recommended to use an Allen wranch, as this tightens the bolts more firmly. Furthermore it is smart to first loosly tighten the bolts and then when the pieces of extrusion are in the right place tighten them.

Next add the piece of extrusion of 40 cm in the center of one of the sides of the base perpendicularly. Use herefore 3 angle brackets and 6 bolts.

Last of all add the 20 cm piece of extrusion perpendicularly to the top of the 40 cm piece. Use 2 straight brackets, 1 angle bracket and 6 bolts.

The final result should resemble a sort of 'hangman' setup as shown in the images.

For step 3, we are first tasked with adjusting the plexiglass tube, before this can be assembled to the frame created in step 2.

To adjust the plexiglass tube, place it in a vice, to ensure that the plexiglass tube does not dent, it is recommended to place a dishcloth between the vice and the tube. Now a slot can be made at the desired heights, in our case we wanted 3 slots, with the help of a saw. The slot should be made until halfway the tube. On the other side of each sloth, make a tiny slot also using a saw.

Next one can drill a hole. To do so, first drill a tiny hole and then from there on, one can drill a bigger hole. Make sure the hole is the right size for the bolt to fit trough.

Now that the sloths and the hole are made, use a Dremel to make the sloths 3 mm wide. This can be done by carefully placing the Dremel on one side of the sloth to widen the sloth. Make sure that the Dremel has the right speed. Also turn the plexiglass tube in the vice to ensure enough sight and to ensure that one holds the Dremel right while using it. When using the Dremel always make sure to wear eye protection.

To finish the sloths, file them manually.

Now that the plexiglass tube is done, it can be attached to the frame created in step 2. First add a angled bracket on the end bottom of the top piece of extrusion. Make sure that one of the sides faces the air, so that one can add the tube to this. Place a bolt in the hole of the tube, where the head is on the inside of the tube. Carefully put the rest of the bolt through the hole of the free angle bracket. Use a open-end wrench to tighten the nut. Make sure to not tighten this to much, since the plexiglass tube has a change of split.

In order to create an entertaining setup, we will create a LED strip display showing the piezo electric effect. In order to hide the electric components (arduino, wiring, etc) we will first create a small housing from lasercut plywood, after which we can hide the arduino.

Step 4 begins with designing a wooden box to fit all components inside. Using the makercase website, we create and download the box. The box must be able to contain the following items:

1. Small breadboard
2. Arduino Uno
3. LED Matrix MAX7219 Module
4. Wires
5. Battery (9V), powerbank or socket

Given the parameters of these items, the inside of the box should be about 17 x 12 x 7 cm. After downloading the schematic, manually create a 12.9 x 3.3 cm slot in Inkscape or any other editing program. The first two images show the unglued vs glued box. Make sure to not glue the top of the box, otherwise you might lock up your arduino!

As for the electronics, we only need to connect two 'components' to the arduino. Easy enough, right?

First, the LED matrix. Notice how it has 5 pins sticking out of the edge. We need to connect them like this:

1. VCC --> 5V
2. GND --> Breadboard common ground
3. DIN --> pin 11
4. CS --> pin 3
5. CLK --> pin 13

This might sound confusing, so you can also follow the colored wires from the attached image. If you do it this way, make sure the black wire (ground) is connected to the breadboard, since we need a few more wires attatched to ground. If this is still too difficult, you can also follow this guide website, providing a detailed overview of how the LED matrix works (as well as some fun examples!).

After this, we connect the piezo positive (red wire) to the A1 pin of the arduino and the piezo negative (black wire) to the common ground. Then the final step is connecting the common ground to the arduino GND pin, and voilà.

As for the code, download the file named Led.ino. If you use the Arduino IDE app, you can upload this code to the arduino, and it should then function properly.

After this has been set up, you can put all the electronics inside the wooden box, and connect the piezo wires through a hole in the corner. Electronics and housing, check ✓ !

To assemble everything together, we first need to make the set up of the tupperware. We used a tupperware, 10 by 10 cm, inside there were 2 layers of filt then the piezo element was attachted to the top of the filt and then 1 layer of spons was added. This is all to make sure that the mass will not break the piezo elements and that the Arduino will not explode.

For the mass we used a 3D printed white box which was made of 20g of pla filament.

Now that everything has been set up, there is only one step remaining. One simple step: put the piezo, which is in the tupperware underneath the drop mechanism. Make sure that the piezo element is right underneath the drop machanism, to ensure a stable ouput. Really, thats all. It should just work if you load the drop mechanism up and trigger the piezo. However, if there is trouble, here is a list of common mistakes and how to fix them.

1. The display doesn't show a reading --> seperate the drop mechanism and the electronics+housing and check for the following: are the wires set up correctly? Make sure they are on the correct pins, and are firmly connected. Check if the piezo plus and negative are not mixed up. Finally check if there is a voltage source connected to the Arduino (either a battery or a power socket).
2. The dropped weight doesn't fall on the piezo element --> try to move the plexiglass tube a bit to the side, to make sure it is centered above the piezo element.
3. The display always fills up completely --> place some foam above the piezo element to lower the impact of the weight falling on it. This should reduce the volts produced.

If everything now functions properly, you should have a wonderful physical demonstration that shows the transfer of kinetic energy into electrical energy.

That's all folks!