**Patent Pending - United States 61928067**


What is piezoelectric energy harvesting?
Piezoelectricity translates to “electricity from pressure.”  The prefix piezo in Greek means to press or squeeze.  Piezoelectric materials exhibit the piezoelectric effect.  This allows a mechanical force to be applied to the material to deform it slightly and the material will produce an output electric power.  This is done by rearranging the dipoles of the piezoelectric material.  This rearrangement causes a change in the dipole density and therefore a change in the electric field between the dipoles.  Because of this change in the electric field, the piezoelectric material produces an output electric power.

What will be accomplished in this Instructable?
Completion of this Instructable will result in a piezoelectric energy harvesting "boot."  With use of other electronic components, this unit will be able to power other small devices that have a low power consumption.  Total project cost (for 1 unit) is ~ $100.

Step 1: Decide What Size the Unit Should Be. Draft It in a CAD Program, Both in 2D and 3D.

When drafting, be sure to know the size of the piezoelectric disks that will be used.  Consider spring placement and sizes of springs.  The springs that were used in this unit were about 1.5cm in diameter.  Think ahead to all aspects of design from disk placement, spring placement, to where guide bolts will be placed and connecting bolts will be placed.  Also think about wire management.  The wires can sit next to the disks, but it doesn’t look neat and clean.  It will be helpful to see all of this digitally when it comes to assembling the unit.

Step 2: Draft the Stoppers and Holders and Impact Rods.

These will need to be created in a 3D program such as AutoCAD or equivalent, as they need to be made with precision.  They will be exported to a 3D printer.  One impact rod will be needed for every disk used, and the stoppers and holders will be needed for each spring.  The stoppers and holders must be a cup shape and one will be needed for the top plate and one for the bottom plate.  The cup shape is used to hold the spring in place.  The additional function of these holders is to act as a stopper for the descending top plate so that the impact rods do not deform the piezoelectric disks to fracturing point.  The impact rods were made 1mm longer than the sum of the length of the top and bottom stoppers and holders.  This allowed the impact rods to deform the piezoelectric disks 1mm, which is a safe and highly effective deformation distance for the disk elements used in this model.

Step 3: CNC the Top and Bottom Plates.

MDF board was used since it can be purchased flat, while other boards can be slightly warped.  The CNC machine requires likely either a .dwg or a .dxf file to be loaded into software to create a tool path.  The entire plate was milled – from the details to the actual cutting of the edges.  It would be smart to have the holes for screws and bolts drilled with the CNC as well, as this would greatly increase the accuracy of the holes.  After the boards are cut out, be sure to sand the insides of the troughs and holes if the CNC did not make them very flat.  Higher end CNC machines will likely take care of this for you.

Step 4: Assemble and Test the Mechanical Assembly.

Attach the spring holders and stoppers to the plates.  Holes must be drilled in them first to allow the bolts through.  Place one 1/4 inch washer on the 1/4 inch by 3 inch bolt before putting it through the plate.  Once through the plate and the cup, place a 3/8 inch washer on the bolt and then another 1/4 inch washer, followed by a nut.  Do this for each of the 8 cup bolts.  Tighten finger tight with a socket wrench.  Place a spring in each holder and stopper, then place the top plate on the springs making sure that each spring is sitting in both a bottom and top part of the holders and stoppers.  Put two 1/4 inch washers on each of the 1/4 inch by 6 inch carriage bolts.  Place the carriage bolts in the corner holes of the top and bottom plates, inserting them up through the bottom plate and then through the top plate.  Place two more 1/4 inch washers on the carriage bolt and then a nut on each.  Tighten so there is about 1 inch of space between the washers and the end of the carriage bolts.

Step 5: Attach the Impact Rods.

The unit will have to be disassembled to do this.  Be sure to drill small holes in the impact rods before trying to screw them in.  If the holes are drilled in the MDF board from a CNC, disregard the next sentence. If the holes for the screws were not drilled with the CNC, a printout of the 2D CAD file with circle centers marked will have to be taped to the top plate.  This will allow for relatively accurate holes to be drilled manually.  Screw in all of the impact rods.

Step 6: Solder All of the Piezoelectric Disks in Parallel.

It was found to be much easier to solder 3 elements together at a time, leaving 6 groups of disks wired in parallel.  Then solder these groups in pairs, leaving three groups of six piezoelectric disks.  Lay these three groups out how they will appear on the base plate, and then solder them together.  Lastly, solder two longer wires to the end of the disk circuit.  These will be the output wires to the load circuit.  Note that the leads on the disks are very fragile and will break with too much tugging.  Be careful, of there will be a lot of wire stripping and re-soldering to do.

Step 7: Apply Electrical Tape to the Solder Joints.

The wires will be very close together in the unit and can move easily.  Applying a small strip of electrical tape over each solder joint will ensure isolation and prevent any shorts.

Step 8: Test the Circuit.

Before adhering the disk circuit to the base plate, test the circuit with a multi-meter.  Be sure to test each individual disk for an output voltage.  Simply tap on them and there should be some voltage.  Doing this will ensure that each disk is connected properly in the circuit and that there are no faults in the circuitry.

Step 9: Hot Glue the Piezoelectric Disks to the Base Plate.

Apply a small dab of hot glue to four sides of the circles on the base plate.  Press the disk down on the hot glue.  Repeat for all of the disks.  It is easier to start with the middle disks as wires begin to get in the way quickly.  Be careful with the wires as well, as they can break off easily – no hard tugs!  Use a piece of wire or other means to tie or attack the center circuit wires to the spring holders and stoppers.  This will keep them out of the way of the impact rods.

Step 10: Assemble the Unit and Test It.

Put the top plate back on.  Connect the output wires to a multi-meter and test the unit.  Make sure it slides smoothly and that the wires are not in the way of the impact rods.

Step 11: Build a Load Circuit.

This can be anything, though LEDs are a quick and satisfying load and demonstration of piezoelectric energy harvesting. The load circuit used in this project included 12 LEDs wired in parallel. One of the most important pieces of the load circuit is a full-wave bridge rectifier. A full-wave bridge rectifier flips the negative voltage spike and makes it a positive spike. This will be needed if capacitors are a part of the load circuit. The output power is also doubled when using a full-wave bridge rectifier. A half-wave bridge rectifier would also work, but the power would be half of what a full-wave would provide. Additionally, depending on what the load circuit involves, capacitors could be used for storage or voltage regulation, and linear regulators could be useful for voltage regulation.

**Depending on what you want to do, you may find step 13 in Angelo's Instructable quite helpful. He discusses hooking the generator up to a battery to store and later use the produced energy.

Step 12: File Downloads and Resources

To request project files, do one of the following:

  • Download directly (below)
    • Write-up
    • Circuit diagram
  • Post a comment on this Instructable with your email address
  • Send a direct message to me on Instructables


I STRONGLY encourage questions and comments, so PLEASE feel free to contact me. I usually respond within a day or two!


Project Files
File Descriptions:
Piezo_bottomplate_3D.dwg - Base plate in 3D. File has layers.
Piezo_plates_CNC.dwg - Base plate and top plate for CNC router (2D)
Piezo_plates_CNC.dxf - Plates for CNC in DXF file type
Presentation.pptx - Powerpoint presentation
Impact_rod.stl - Impact rods (18 printed on 3D printer)
Stoppers_holders_base.dwg - Stoppers and spring holders (base) (CAD file)
Stoppers_holders_base.stl - Stoppers and spring holders (base) (3D printer)
Stoppers_holders_top.dwg - Stoppers and spring holders for top (CAD file)
Stoppers_holders_top.stl - Stoppers and spring holders for top (Printer file)

Resources and Research Files
File descriptions:
PyzoFlex.pdf - PyzoFlex - Printed Piezoelectric Pressure Sensing Foil
Images SI Inc.pdf - Piezo Film Sensors - Technical Manual (Images SI Inc.)
MIT.pdf - MIT-Modeling and Design of a MEMS Piezoelectric Vibration Energy Harvester
JR-EAST.pdf - JR-EAST Piezo Floor
APC.pdf - APC International, Ltd. - First Steps Towards Piezoaction
Piezoelectricity wiki.pdf - Wikipedia page on Piezoelectricity

For questions, comments, resources, or any other inquiries, please feel free to post comments or send direct messages on Instructables.

**If anything from this Instructable or any of the attached files is used, please credit references accordingly. Thank you and enjoy!**

I wanna ask where can i get those piezoelectric generators which its shape is rectangle thanks
Well, you can't really buy the rigid disk in a rectangular shape. There are piezoelectric "flaps" or "sheets" that you can buy, but I think you may find them to be challenging to apply as used in this instructable. They're also usually pricey as they're typically used for more sensor-like applications.
<p>can you help me, i have similar project.</p><p>i hope you sent me, edysetiawan1945@gmail.com. ok thank you</p>
Hello! I have updated the instructable. The files you're looking for are now attached to the last step. If you'd like any of the other files (STLs, reference materials, etc.), comment back here and I'll get those to you.<br>Happy building!<br>Ryan
<p>Good afternoon sir. I sent an email to you. I hope you can have the time to look at it. hope to hear from you soon</p>
Hello, great to hear from you. I did get your email and will be sure to reply this afternoon!
Please I'm working on similar project. I would be greatly glad if i get the project file too. Thank you. emmanuelolubo@yahoo.com or temidayoolubo@gmail.com
<p>Sent! :)</p>
<p>Could you send me the project files as well, please? thanks!</p><p>alissachantalbatista@gmail.com</p>
<p>plz i want to download these project files to use them </p>
<p>Could you please send me project files to my mail:</p><p>ahmed.settyet@yahoo.com</p><p>Thanks in advance, appreciated.</p>
<p>please send me the project file to my mail.</p><p>kumbharchetan0505@gmail.com</p>
<p>could you send me the project files as well? thanks!</p><p>jman93624@yahoo.com</p>
<p>can you send me the project files? thanks a lot!</p><p>email address: angelateoz@gmail.com</p>
<p>hiiii can u send me the files? plss? i need it for my research projecttt plss. send it at @denillll@yahoo.com thank you. God bless!</p>
<p>Hi! Your project is awesome! May I get a look at the project files? The links have expired. Do you mind emailing me the files? </p><p>alxxlalx@gmail.com</p>
<p>hey sir can you please send me design and research files to my mail.?</p><p>if you could do this so please send it my mail id is dhruv.b.parekh@gmail.com</p>
<p>Is there any chance of me getting to see the project files because all of the links have expired?.</p>
<p>Hello there. Salam from Malaysia. May i know, on your 12th steps page, there is a link for downloading this material for research and reference. may i know, is there an alternative link to download the folder? apparently, the link is too old and propably deleted. please help, thank you.</p>
<p>Where do you buy those piezo electric generators?</p>
One small point which occurs to me which could affect the efficiency. If you have connected the piezo units directly in parallel are you not losing power due to the output of one of unit driveing the other units if there is a difference in the phase of the voltage being created? Only if pressure was applied absolutely parallel to all devices would they all produce in phase. Or did this have little effect in practice?
kintekobo,<br><br>It is extremely likely that your hypothesis is correct. Pressure is not (though pretty good considering design constraints) applied absolutely parallel to all disks at the same time. Therefore, it is just about given that the devices are not in phase. This is likely a major part of the lack of efficiency of the unit. I believe that another major problem is the gauge of wire that was used to connect all of the disks in parallel. It is much larger in diameter than the wires coming off of the disks, which means that a lot of power is probably lost to resistance in the circuit. At the the time of testing the unit, I did not have the tools to measure whether the devices were in phase or not, so I cannot conclude that this is a definite issue, though as previously discussed, quite likely so. Given the lack of measurement tools, I concluded that power was lost mainly due to resistance. <br><br>Thank you for your ideas - they will be considered when making improvements to the device!<br><br>Ryan
How much electricity by one pizo is produced?
I cannot remember the current produced from one disk... I think it was about 30V and low milli- or high micro-amps. I have some data in my .PDF about the project. Unfortunately, I did not have enough time to take and record good data for this unit, though it was not required for the project anyway. I will try to gather some data in the near future as this is a common inquiry.
What was the final output? <br> <br>Did it actually work as a boot sole?
Please see above reply to rimar2000 for your first question. <br> <br>The device was indeed tested as a &quot;sole&quot; of a shoe. It was placed on the floor and stepped on to mimic walking. Velcro straps or some other means of attachment to the foot or shoe could be put on the unit to actually use it while walking. With an increased price and some design considerations to make the unit smaller, it could actually fit into the sole of a shoe AND have a larger output.
So, in it's current form, it's more useful as an energy-harvesting floor - put it under a panel in the floor of a corridor?
Yes, that would be a more plausible application of the existing unit. To operate as a &quot;shoe&quot; or shoe sole, the unit would have to be smaller. The large size of this unit reduces cost as well as exaggerates operation for comprehension of the concept of piezoelectric energy harvesting for the non-scientific minds.
This is a very useful project, but the main question is &iquest;is it useful? &iquest;How many Volts x Amps it brings?
This is a low power source. With a good strike, each disk produces about 25 volts. I do not have my research papers with me at this time and do not recall amperage, though it is in the range of single-digit mA or high uA...In other words, very low current. Many disks together can provide enough power to light a hallway. You may find the file on page 12 entitled &quot;JR-EAST.pdf&quot; to be helpful in answering this question.
No video? You should make a video.

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