A Pendulum should really work

[elgersmad]

@elgersmad: sorry, I have difficulties imagining a circuit from words. May be you could draw your circuit and post it.

I am afraid, the piezo elements are not able to power an OpAmp. The one you mentioned has a
Quiescent Current per Amplifier of 25µA at 6 Volt resulting in 150 µW.

150 µW is a top performing multilayer special production piezo element for "energy harvesting". What we will see from inexpensive run of the mill piezo elements is less (hopefully 10 µW)

Equation Reference

Piezoelectric materials produce voltage and current based upon Force and Time.  The more force that is displaced over a shorter period of time, the more energy is produced.  Hit it hard, get a high voltage, press on it, get a low voltage. If the leads are shorted, all you get it current, if the leads are open all you get is voltage.  For you to say, you know how much energy that there will be, is not even based upon a real answer.  In effect you're just spouting.  You can't tell me how much energy my pendulum will produce when I can predict that.  But, if I change the weight of the pendulum, that changes the peak voltage and current.  There's a list of things that can change and would change the output.  But, you are not doing the math and really are taking about some kind of sensor result from the top of your head.

If you were so right, this device wouldn't even work, and Piezoelectric Transformers are typically 90% efficient.
A Piezoelectric Transformer

90% of 40 watts is 36 watts.  The Piezoelectric Vibration Harvesters are really garbage.  But, what you are saying doesn't even allow a piezoelectric lighter to have enough energy to light a flame.  Check that one out in Joules.

For the amount of stress PZT can handle, it needs a lever and a fulcrum like a pair of pliers to pinch on the piezoelectric ceramic disks.  That fulcrum would be at a 90 degree angle away from the pendulum's axis.  Every time the weight comes down, the pliers bite onto the ceramic disks.  0 to 80% of the peak amount of stress that the element can handle is ideal.  So, when the pendulum swings, the pliers bite starts at zero, goes up to 80% then drops down again.  But, you are wrong.

[conradelektro]

What I said about the energy (current) coming out of a piezo crystal is what I read in articles about piezo electricity. The intention is to use all available information in order to have reasonable expectations. Yes, I know nothing, but I can read.

Only experiments can tell how much electricity can really be harvested by piezo crystals from a pendulum or a vibrating table (carrying an imbalanced wheel). So, till I have built something, I have nothing more to tell.

A pendulum is nice, because it is slow and quiet, but it will need a lot of room. An imbalanced wheel can be smaller. So there are advantages and drawbacks which have to be used or overcome by real experiments.

Greetings, Conrad

[elgersmad]

A pendulum is nice, because it is slow and quiet, but it will need a lot of room. An imbalanced wheel can be smaller. So there are advantages and drawbacks which have to be used or overcome by real experiments.

Greetings, Conrad

You are right!  There is a way to use a balanced wheel, and I've figured out.

I was watching this Video

Basically, what you need is a potter's wheel, and for some-one to make a rotor.  The real difference between it and the SEG, is that the rollers are in a race just like a set of roller bearings.

Roller Bearings Picture

The outside race would need to be made from ceramic.  The bearings would be turned from the center by a motor, and not kicked along like the SEG by a solenoid.  They would be heavy rollers but, the whole wheel and assembly would be balanced.  Now, the ceramic race, would have 1cm segments of piezoelectric ceramic PZT embedded inside the wall.  So, as each roller passed over it, the centripetal force would press on the Piezoelectric Ceramic as the roller passed over it, and relieve it as the roller moved away.  The RPM would generate centripetal forces that would increase the apparent weight of the rollers.  So, if everything rolls freely, and there are spokes that lead to the roller bearings mounting as in this picture:

roller bearing Mount, that should have spokes to be turned from the center

It's just that the rollers should be in slots, so that when they go to press on the sides of the ceramic race, they can press on the sides as hard as the centripetal forces will allow.  Ceramic, can be as hard as steel, even harder and retain allot of stress.  But, if you drop it, it breaks.

After that, the piezoelectric ceramic, would need to be machined into place to make sure that the race was smooth and retained a low friction.  For the most part it's a centrifuge.  The larger the radius, the more force is experienced at a given RPM.  Being balanced, it doesn't require allot Horsepower even in a fractional sense with reduced friction being the main point of the whole assembly.  PZT is very hard.  It really only compresses by a few germs Micrometers.  Even normal metals do that much flexing under a microscope.  Manufacturing the device would be the most difficult.  You could couldn't put the electrodes on it until after the race was machined smooth so that the rollers just roll on it, and don't hit any bumps.

[gyulasun]

What I said about the energy (current) coming out of a piezo crystal is what I read in articles about piezo electricity. The intention is to use all available information in order to have reasonable expectations. Yes, I know nothing, but I can read.

Only experiments can tell how much electricity can really be harvested by piezo crystals from a pendulum or a vibrating table (carrying an imbalanced wheel). So, till I have built something, I have nothing more to tell.

A pendulum is nice, because it is slow and quiet, but it will need a lot of room. An imbalanced wheel can be smaller. So there are advantages and drawbacks which have to be used or overcome by real experiments.

Greetings, Conrad

Hi Conrad and All,

Here are some useful links on energy harvesting piezo devices, discussing their possible performance efficiency etc.  I just found them in the Kapanadze thread here:
http://www.overunity.com/index.php?topic=7679.msg280281#msg280281 

The last link shown there leads to a patent application, without Figures, here is a direct link to the full text + Figures + photos of the setups:
http://www.wipo.int/pctdb/images4/PCT-PAGES/2010/522010/10151738/10151738.pdf 

Gyula

EDIT: here is another paper: http://www.heathhofmann.me/IEEETransPelvol18no2march2003.pdf 

[conradelektro]

Hello Gyula!

Thank you, very nice information about piezo elements, specially the step down converter clarifies many questions I had. The setup from the patent would be difficult to reproduce, but it shows what could be done.

I ordered a few parts and will build a simple "shaker" with an imbalanced wheel driven like a pulse motor beating on piezo elements. It has been done before, but I want to see it myself.

I want to use toroids with an enameled copper wire winding, because I built such a pulse motor when the STEON-Craze was starting. It turned nicely with little energy but was not OU of-course. I posted a reed switch circuit and a photo of the toroids further up in this thread.

It will take some time to build, but I will post it here eventually. I just want to see how much one gets out of a stack of standard piezo elements (for buzzers) and how well a simple shaker (based on the pulse motor principle) performs. Does it really take just a little energy to lift an imbalanced wheel over its dead point?

The pendulum idea also has to be really built to learn more. It seems to allow for heavy weights bearing down on piezo elements (although with very little frequency). It also needs some experimenting to come up with a very efficient  "drive" for a pendulum. Everybody seems to know that it takes very little to keep a heavy pendulum going, but I never saw a convincing drive mechanism using and producing this famous "very little energy". It would also be useful for a Milkovic pendulum.

I learn most by building crazy stuff and it is also fun. It needs a childish type like me to enjoy all sorts of Joule Thief lamps in my house day and night. And a turning motor (however stupid it is) gives me pleasure.

For people who like microprocessors, I want to report that the TI LaunchPad serves me very well lately when building little projects. It is very well priced, robust and simple to use (all necessary software is for free on the Internet). Some sneer at the 16 MHz, but it is plenty for many applications. One also has communication with a PC via USB, which allows to display measurements at the PC or to control something from the PC (although you also have to write a program on the PC, e.g. with VisualBasic or VisualC):

http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_(MSP-EXP430G2)?DCMP=launchpad&HQS=Other+OT+launchpadwiki

http://newscenter.ti.com/Blogs/newsroom/archive/2010/06/22/ti-s-new-4-30-launchpad-is-a-complete-development-kit-for-harnessing-the-ultra-low-power-and-16-bit-performance-of-msp430-value-line-mcus.aspx

Greetings, Conrad