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## Gravity powered devices => Gravity powered devices => Topic started by: elgersmad on March 29, 2011, 12:16:54 AM

Title: A Pendulum should really work
Post by: elgersmad on March 29, 2011, 12:16:54 AM
I know how effective a pendulum can be by itself.  Add too much to that or take too much away, and it won't work so well.  The key point is really the fulcrum of the movement.  If you support it the right way with piezoelectric disks, it should work wonderfully.

First you take a stack of piezoelectric rings, and make all of your electrical connections.  Then you send rod through it that has a universal joint just below the stack of piezoelectric ceramic rings.  They don't really move much a few millionths of an inch to generate electricity.  So, as the pendulum reaches the bottom of it's swing, all of the downward energy is then sent through the stack of piezoelectric rings.  A flat washer holds the top end of the rod in place over the stack, and the universal joint hangs out below the stack.  The more massive the weight, once it's swinging won't loose much energy due to the compression of the piezoelectric disks.  If the height of the swing is nearly 90 degrees from vertical, and nearly horizontal for the length of the swing arm, almost all of the weight will have been taken off of the piezoelectric ceramic.  That produces the pumping action to generate electricity.  When you stack disks, the square area all experiences the same amount of force no matter how high you stack the piezoelectric disks until their own weight doesn't allow for decompression.  So, you could stack nearly 20 or 30 of these disks on top of each other.  I think a bowling ball or several hundred pounds of weight would work and a solenoid to keep the swing height to peak would use the least amount of energy, if and only if the solenoid's plunger is almost all the way in and it's a pull type solenoid.  Just to add enough force to make sure that the swing height is always exact.
Title: Re: A Pendulum should really work
Post by: conradelektro on March 29, 2011, 07:15:21 PM

I like the idea. Could work with various pendulum arrangements, as long as pressure is put on many piezoelectric elements.

Also pressure along the swing plane could be harvested, as in the attached drawing.

Just by chance, do you know a good source for piezoelectric elements. One would need a lot of them (like 20 or 30, as you say)?

Title: Re: A Pendulum should really work
Post by: gyulasun on March 30, 2011, 12:02:56 AM
...
Just by chance, do you know a good source for piezoelectric elements. One would need a lot of them (like 20 or 30, as you say)?
...

I do not know if this is a good price or not, a first search at RS brought this:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&binCount=1&Nty=1&Ntx=mode%2bmatchallpartial&Ntk=I18NAll&Ne=4294957561&Nr=AND%28avl%3auk%2csearchDiscon_uk%3aN%29&N=4294953991&Ntt=piezo

it is a vibration sensor. If I find later some other sources, will post.

Possible problem can be they have very high electrical impedance and a clever way of matching is to be found to get the most out of them. MAybe resonating them with a suitable step down transformer.

Gyula
Title: Re: A Pendulum should really work
Post by: elgersmad on March 30, 2011, 07:58:17 AM
Think simpler.  The more moving parts the more friction.  It's real basic.  When the weight is in the position I drew it in, the most weight is displaced on the ceramic disks.  When it's at 85 to 90 degrees and the weight has swung up as high as it can go, it takes the weight off of the axis.  Just like on a swing when you swing high, the chain goes slack and then you drop and jerk then continue to swing.  Too many axis will act like a chain.

When the plunger of a solenoid is almost all of the way in, it has the most pull for the least amount of power in volts and amperes of current.  So, you want the solenoid to pull as the weight is still moving toward it and add to it's velocity and keep the swing height to the desired height, where a chain on a swing would go slack and there's no stress on the piezoelectric.

You were very close based upon my description in words.  Mentally, you just didn't draw the same picture.  Those other piezoelectric elements would stop the pendulum from swinging just because they would take stress from the axis.  It might be a good idea to use just two axis as you've shown and connect the solenoid between the two.
Title: Re: A Pendulum should really work
Post by: elgersmad on March 30, 2011, 08:01:51 AM
And I found a good place to get Piezoelectric Ceramic Disks, Plates and Rings (http://www.steminc.com/)

I don't think it'll be too cost effective to buy more than 2.  But, they are quality components.  I don't think that they should be soldered into place.  But use a combination of washers.  Nylon as an insulator, plastic tube to keep the sides from touching the bolt.  A couple of drilled holes in single sided copper clad circuit boards to get a connection in and out of there but, no direct soldering in order to keep an even amount of pressure on the disk via the stiff wash above the nylon washer and so one.  Don't allow metal to touch the sides of the piezoelectric disks.  Don't let any metal touch the disks that are not used to collect power.
Title: Re: A Pendulum should really work
Post by: conradelektro on March 30, 2011, 08:45:34 AM

thank you, good places to buy piezo elements.

I do not understand piezo elements well enough. May be the frequency only matters when producing sound (by applying voltage)? In case of low frequency pressure, one probably can use any version of a piezo element?

I was thinking about stacking simple and reasonably priced elements like the one I attached (Piezo Element Farnell order code 1675548). They cost 54 Cents (Euro) a piece.

The metal plate is there to make a sound (bending up or down), but would not matter when stacking these elements.

The wires are already attached which might be useful. To build a stack, one could put acrylic discs in between to spread the load and to have room for the wires; making a cut out (slit) in the acrylic disks for the wires and the place on the piezo element where the solder might pose a problem when stacking these piezo elements.

It might be difficult to attach wires to a raw piezo crystal?

May be it is better to stack many elements instead of using one bigger crystal?

We need to find a specialist for piezo elements to clarify basic issues:

- Does the metal in vibrator type pieco disks matter when applying pressure?

- Stack of many elements or one bigger crystal?

- In which way does frequency matter when applying pressure?

- How to attach wires to a crystal?

- Is it important to spread the load over the whole crystal when applying pressure?

Title: Re: A Pendulum should really work
Post by: elgersmad on March 30, 2011, 10:36:43 AM
We don't need a specialist.  I can read the specs.  I ordered 10 disks that are all about 1cm in diameter.  The solder is part silver. It sticks to copper, steel, silver, gold, don't worry about solder.  You shouldn't be soldering the type I've shown you.  You might go somewhere that they gold emboss bibles to personalize them to buy some gold leaf.  That will prevent the silver coating from oxidizing.  But, literally, you just rub gold on with a tool, like a plastic toothpick.  You can almost draw it on with a pencil.

Frequency, really applies to resonance and sound power.  If you positioned the cheap ones around the bolt, and the washer was wide enough equalize the pressure on three, that might work.  Those are polymer based piezoelectric disks, if you're looking at the one in picture.  At a high frequency of compression, they would actually heat up and melt.  The pendulum won't hurt em'.  If you want something that is cheap and hard, try a ceramics class.  Ceramics have a high compression strength and can be stronger than steel.  Yea, if you drop it, it will break.  But, if it's just stress coming and going, ceramics can handle allot without special purpose ceramics.  5 bucks bought me so much clay, I still haven't used it all, and it's almost been two years.  It only cost a couple bucks to get a small item fired and then I have a part I need without paying and outrageous price.  They key is working it leather hard, once you've taken the class.  Cutting it with an exacto knife, sanding it, wetting it to add a little if you must or to fix a mistake.  If you are very very careful, you can place a piece of ceramic between two neodymium magnets of any size.  It will break if the magnets clack together.  But, if you can figure a way around that happening, then it won't break.

I wouldn't stack those piezoelectric disks were showing me.  But, I would use three.  An equilateral triangle distributes force equally on all three members.  If you used a bowling ball as a pendulum, about 15 to 30 volts max.  Mostly a current, unknown value.  And that really depends upon how equally distributed the weight is.  That's just educated guess.

Here's a simple demo:

Now, this guy has built a solenoid that could be so efficient that it would work with the whole idea.

Needs more grease.

Title: Re: A Pendulum should really work
Post by: conradelektro on March 30, 2011, 11:28:46 AM

Do you expect that the 10 discs with 1 cm diameter (which you ordered) give more Voltage and Amperage than the buzzer disk I talked about?

This is the same question as: Is it better to use a bigger crystal than a thiner one?

Or: what is the special feature of the disks you ordered, that made you choose them?

Title: Re: A Pendulum should really work
Post by: elgersmad on March 30, 2011, 11:45:27 AM
That's for a different project.  I was simply stating that I had bought some...  It's enough to test my idea.  But, I think it has been done before and I just can't find an article or technical paper on the subject.  I'll find out, quick enough.
Title: Re: A Pendulum should really work
Post by: conradelektro on March 30, 2011, 07:39:18 PM

The output is proportional to volume, so a bigger piezo junk gives more Voltage and power. But there seems to be a limit, therefore they usually build multiple layers.

Now, how much output can be expected? Well, this is discouraging, the best achieved is in the order of a few 100ÂµW (not even a Milli Watt) per actuation (for a very short time).

So, the usual way to handle this is to have a few million actuations per second. A pendulum therefore is not good, one should have something turning fast, beating very often against the piezo crystal.

May be one should think about a heavy unbalanced flywheel turning with 1000 revolutions per minute or more. The unbalanced flywheel should only be slightly unbalanced so that it can turn very fast. The piezo elements are somewhere near the axis of the flywheel which wants to wobble.

The problem, can one get enough electricity from the piezo elements (see drawing) to drive the flywheel? May be with a pulse motor, the flywheel having evenly spaced magnets on its circumference (or at least one magnet opposite the mass).

Title: Re: A Pendulum should really work
Post by: conradelektro on March 30, 2011, 08:13:28 PM
An other idea:

A unbalanced flywheel is fixed to a table and the table rests (swims) on twelve piezo elements harvesting the electricity from the vibrating table.

The flywheel could turn very fast and does not have to be very unbalanced to induce vibrations into the table (20 Hertz = 1200 rpm). May be there are higher frequency harmonics building up in the table if the table is 2 mm steel.

I imagine a 250 mm diameter flywheel made from 10 mm acrylic with one heavy magnet, which is for the pulse drive and is at the same time the mass for the imbalance.

Title: Re: A Pendulum should really work
Post by: elgersmad on March 30, 2011, 10:12:40 PM
It'll work.  But, you'll need to bolt down your generator or it'll be walking all over the house.  How many vibrating pets do you have?  How about sticking that eccentric wheel on a plywood dog cutout?  One big angry chuaua.  The imbalanced wheel is a good idea.  If you use really good bearings and solid mounts it might even last awhile.  Given a push, wouldn't take much energy to keep going.
Title: Re: A Pendulum should really work
Post by: conradelektro on March 30, 2011, 11:32:18 PM
Attached a possible pulse drive circuit with piezo elements.

The reed switch is not a very good solution, but will work with very low power. For proof of principle it will suffice.

One can add more piezo elements, each one needs four diodes. Stacked piezo elements might be connected in series?

The pulse drive could also be used for a pendulum.

In general (imbalance wheel or pendulum) the power from the piezo elements should not be enough to drive any setup as a perpetuum mobile (according to accepted theory of everything).

I will go hunting for parts, just for fun, it is weird enough to be built. Should not make a racket as long as the flywheel is driven rather slowly.

May be someone has an better idea how to drive an imbalanced flywheel with piezo elements. Better circuit to harvest the energy from the piezo elements? Other drive method?

Title: Re: A Pendulum should really work
Post by: elgersmad on March 31, 2011, 12:36:27 PM
I would use a higher impedance circuit.  The reed switch uses power, like anything else.  But, MOSFET OpAmp would use less power triggering Power MOSFET, MESFET, or IGBT.  Battery saver style ICs can do a better job and use less power, even when the MOSFET kicks in to dump the capacitor.  A Piezoelectric Element works as a source of AC.  When you compress electrons move in one direction, as it decompresses electrons go back to where they came from.  So, every element requires a bridge rectifier.  They have no real polarity even though they often connect red and black leads when you're generating power.  It's like a sponge filled with electrons, they leave one side of the disk and go to other when you compress it.  The electrons return to their initial starting point when the disk decompresses.

You have a bridge rectifier and connect the cheap piezoelectric disk too it.  Then you'll get a pulse of light from a single LED when you press on it, and again when you let go.  Just a simple bridge rectifier experiment will reveal that.  Just press and keep the pressure on it, then suddenly let go.

Good start though.

The importance of polarity really applies to producing sound and which direction it can move first.  Most piezoelectric materials must be compressed first.  So, which direction the electrons move is important when you are driving it to produce sound.
This MOSFET (http://www.nxp.com/documents/data_sheet/BUK95_96_9E04_40A.pdf)

Then use 2 Zener Diodes in series to control power on after the bridge rectifier.  Then it goes even farther to detect the right voltage based upon a threshold knob.  Open Loop Gain.  When it's on, it's on.  The output of the opamp directly drives the MOSFET's gate.  The capacitor should be a large value and feed a capacitor that holds the ideal charge for a transformer/converter.  So, if we want 10 volts out of the transformer, if we want 30, we can change the turn ratio and have 30.  So, first it fills a fat capacitor to keep the spikes away from our circuit.  Then it fills a small one that will produce the pulse width we want.  Capacitor in parallel, resistor in series with the load, pulse capacitor, zener diode pair in series and parallel with the load.  Then off of the low zener diode the opamp is biased and above the high is the full voltage we want for the MOSFET about 30 volts.  You don't want to dump anything off but if it's just pendulum that should work.

You'd need a higher voltage MOSFET for the eccentric wheel and motor.  That would do allot more faster and may require some effort in splitting up the outputs of the piezoelectric disks to produce a split supply and operate a Bridge H MOSFET Circuit.  FM style relatively high frequency.  On that one, I would really need to sit down with a meter, measure the voltage and current to think about which style of power up I'd want to use.  Basically, when there's not enough, the zener voltage divider prevents anything from getting power or starting up.  The opamp doesn't take enough to hurt that.

If you wind up hearing the circuit, each pulse should the same width when the circuit fires a pulse for the transformer.  The resistor between the large capacitor and the small one is chosen to produce a square wave with a 50% duty cycle maximum.  Each on pulse is always the same width.  The off pulses vary in time with the amount of power produced by the piezoelectric disks.  As the pendulum starts from it's highest point and falls to it's lowest, the frequency of pulses will rise, then when it starts riding back up, it will drop in frequency to almost clicking.
Title: Re: A Pendulum should really work
Post by: conradelektro on March 31, 2011, 03:19:42 PM
@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 25ÂµA at 6 Volt resulting in 150 ÂµW.

150 ÂµW 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 ÂµW).

This is the reason why I came up with the reed switch. The energy for actuating the reed switch comes from the permanent magnet of the pulse drive and does therefore not have to be provided by the piezo elements. All energy (besides the loss in the capacitor) goes into the coil of the pulse drive when the reed switch closes (when the magnet has a certain position near the coil).

I would switch the pulse drive in a "push away" set up: when the magnet is exactly at the mid point (when its natural attraction to the core of the coil is a maximum), the reed switch should feed the electricity to the coil in order to push the magnet away (in the direction of rotation). The reed should stay ON till the magnet is well away from the coil. In case of little power fed to the coil, this means, the magnet is less attracted to the core of the coil than before and can therefore leave the sticky point with a little net gain. The capacitor will be exhausted completely. There will be no electricity left for any active component.

Keep in mind, piezo elements show a "static electricity phenomena" which means rather high voltage (up to 50 Volt), but very very very low amperage.

The US-army wanted to produce shoes which generate electricity when walking by help of piezo elements. Well, they gave up. One had to walk for hours to produce very few Milli-Ampere-Hours.

Attached see a photo of one of my pulse motor experiments. I used toroids instead of coils. The magnet is attracted to the ferrite material of the toroids, but when current is driven through the windings on the toroids, the magnet "does not feel" the ferrite material any more and can leave the sticky point. I like to call that "attract the magnet and then hide at the sticky point". This allows to drive such a pulse motor with very little power (but it will have very little torque). I achieved 800 rpm with 0.16 Watt (no load, just free run). But with the piezo elements it should work with 0.000016 Watt (16 ÂµW), which is to be doubted.

Title: Re: A Pendulum should really work
Post by: elgersmad on April 01, 2011, 02:25:34 AM
Quote
@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 25ÂµA at 6 Volt resulting in 150 ÂµW.

150 ÂµW 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 ÂµW)

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 (http://www.steminc.com/piezo/SMMTF53P4S40.asp)

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.
Title: Re: A Pendulum should really work
Post by: conradelektro on April 01, 2011, 10:44:32 AM
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.

Title: Re: A Pendulum should really work
Post by: elgersmad on April 02, 2011, 02:04:27 AM

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.

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

I was watching this Video (http://www.youtube.com/watch?v=FHq8xnTNA3o)

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 (http://www.ahrinternational.com/classic_roller_bearing.gif)

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 (http://www.bestpricebearing.com/sales1/wp-content/uploads/2010/08/Needle-Roller-Bearings2.jpg)

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.

Title: Re: A Pendulum should really work
Post by: gyulasun on April 03, 2011, 08:24:13 PM
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.

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
Title: Re: A Pendulum should really work
Post by: conradelektro on April 04, 2011, 06:23:13 PM
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):

Title: Re: A Pendulum should really work
Post by: Low-Q on April 06, 2011, 11:48:16 AM
First of all, a pendulum are slow, and the frequency are totally depending on its length and gravity. So, I agree that an unbalanced wheel are the correct approach, because its frequency (or rpm) are not depending on diameter and gravity. It can be made much smaller, with much higher efficiency.

Using piezo electric power source might be useful. However, the output are, as far as I know, depending on the frequency as well as the pressure. A good thing about piezo electric devices is (as probably already mentioned) the requirement of pressure difference rather than mechanical movement to provide energy.
Because an unbalanced wheel have to stay perfectly still during the run in order to not loose energy by its possible viberations. Viberations will slow down / break a spinning unbalanced wheel grately. So therefor, implementing a piezo electric device would probably be the best way because of the minimum viberations, and maximum pressure.

It might therfor be possible to feed back the energy from the piezo electric device into a high efficient motor which powers the unbalanced wheel. Even use the pulses from the piezo to feed directly into an electromagnet which in turn propells a rotating magnet.

The weight which provide the unbalanced wheel must be applied before the magnet approach the electromagnet in order to determine the direction of rotation, and rotation itself.

The magnet can be this weight, and if the coil are not placed at the bottom, but a few degrees later, the coil will be fed with energy in advace of the magnet, so it can pull the magnet towards it and force rotation.

Attached there is a drawing of a simple brushless motor which is powered by pressure on a piezo electric device.

When the magnet is on the bottom, the pressuere on the piezo are greatest. When the magnet is on the top, there is a "negative" pressure so the upper right coil have swapped polarity in order to attract the magnet. Also there should be coils which is repelling the magnet also.

On the other hand, the electricity are probably generated during the pressure difference from no pressure to max pressure, and the electricity reverse from max pressure to negative pressure. So there might be another placement of the coils, but I think you got the idea.

EDIT: The generation will occour when the magnet/weight are between top and bottom. This means that the wheel as drawn will rotate counter clockwise if the piezo are placed either at the bottom, the top, or both top and bottom.

Vidar
Title: Re: A Pendulum should really work
Post by: conradelektro on April 06, 2011, 07:29:39 PM
I did some tests with a piezo element (for a buzzer, sits on a metal plate):

See the attached drawing, photo an scope shots.

The piezo element needs "hits", pressure alone did not do the trick. So, if one builds an imbalanced wheel, the setup must produce "hits", like with a little hammer.

The stroke of the "hit" does not have to be very high, but the "hammer" must hit the element, leave and hit again, leave and hit again, ...

I could charge up a 100ÂµF electrolytic capacitor (replacing the LED) within seconds to 3 Volt (about 5 hits per second), done by hand with a wooden stick (like rapidly making dots with a pencil).

The piezo element was sandwiched by two acrylic disks to protect it. With or without acrylic disks, the performance was about the same.

The low power red LED only gives fairly dim light pulses. I plan to use up to twenty such elements (all in parallel, each one having four diodes, feeding into an electrolytic cap) in "bouncer" with an imbalanced wheel.

Title: Re: A Pendulum should really work
Post by: Low-Q on April 07, 2011, 08:17:13 PM
I did some tests with a piezo element (for a buzzer, sits on a metal plate):

See the attached drawing, photo an scope shots.

The piezo element needs "hits", pressure alone did not do the trick. So, if one builds an imbalanced wheel, the setup must produce "hits", like with a little hammer.

The stroke of the "hit" does not have to be very high, but the "hammer" must hit the element, leave and hit again, leave and hit again, ...

I could charge up a 100ÂµF electrolytic capacitor (replacing the LED) within seconds to 3 Volt (about 5 hits per second), done by hand with a wooden stick (like rapidly making dots with a pencil).

The piezo element was sandwiched by two acrylic disks to protect it. With or without acrylic disks, the performance was about the same.

The low power red LED only gives fairly dim light pulses. I plan to use up to twenty such elements (all in parallel, each one having four diodes, feeding into an electrolytic cap) in "bouncer" with an imbalanced wheel.

Could you load the piezo with a 10 - 20 ohm resistor, and measure the output voltage over the resistor?
Title: Re: A Pendulum should really work
Post by: DreamThinkBuild on April 07, 2011, 09:20:29 PM

I've attached pager motors to piezo's they generate about 119khz sine wave around ~3-5volts ac out not a lot of current(uamps) from my current piezo speakers. The pager motors use very little power 1.5v+@30ma+(lowest).

http://www.goldmine-elec-products.com/prodinfo.asp?number=G17959
http://www.solarbotics.com/products/vpm2/
Title: Re: A Pendulum should really work
Post by: Low-Q on April 07, 2011, 10:25:06 PM
Does anyone here know if  there is a direct relationship between the force and deformation (Force times distance) and the energy output of a piezo?

I have imagined a pendulum with a narrow magnet on it. The magnet pass by another stator magnet which is fixed to a piezo device. Each time the magnet pass by, there will be generated a mechanical pulse into the piezo device (Therfor a narrow (and maybe long magnet). The electric current should then power a small electromagnet which pulls the pendulum in correct phase to sustain the pendulum.

Vidar
Title: Re: A Pendulum should really work
Post by: lumen on April 08, 2011, 01:46:16 AM
Vidar,

Interesting concept!
I have a stack of these piezoelectric disks I bought on eBay some time ago for a similar device. I have been distracted on other projects so it hasn't been built but it was going to be a rotary device with disks around it and each disk would have a full wave bridge soldered to it to convert to DC. The DC was going to charge a capacitor (did some tests on this already) and power a small motor to keep the magnet rotating. The disks deflect very little for a good output and should have almost no drag on the rotating magnet.

Your idea gave me some insight to some other ways to do this also. Thanks!
Title: Re: A Pendulum should really work
Post by: Low-Q on April 08, 2011, 09:40:31 AM
Vidar,

Interesting concept!
I have a stack of these piezoelectric disks I bought on eBay some time ago for a similar device. I have been distracted on other projects so it hasn't been built but it was going to be a rotary device with disks around it and each disk would have a full wave bridge soldered to it to convert to DC. The DC was going to charge a capacitor (did some tests on this already) and power a small motor to keep the magnet rotating. The disks deflect very little for a good output and should have almost no drag on the rotating magnet.

Your idea gave me some insight to some other ways to do this also. Thanks!
I also have an idea of a rotor with lots of narrow and long magnets, and a stator with the same amount of magnets fixed to a piezo each. In theory, the rotor will not require energy to rotate as long as the stator magnets doesn't deflect. However, ther will be cogging, but that is not energy loss by itself. But if the stator magnets deflect due to the compression in a piezo, accordingly to the energy output from a piezo, it will not be possible to make a sustaining motor.

So I have asked myself this:
If we apply 1N of force into a piezo, and the piezo compress 1um, the input energy is 1uJ. The question is then: Will the piezo provide at least the same energy, or will it provide more? Will the piezo provide energy according to the force times distance? Or will the piezo provide energy mainly due to the force applied rather than the force (1N) times distance (1um)?

The problem, as you sure have figured out, is the deflection, and how this will affect the efficiency. Because if the stator magnet doesn't have the same distance to the rotor magnet when the rotor magnet has passed, it will take more energy to enter the stator magnet, than it gives back after the rotor magnet has passed, we have energy loss.

Hmmmm....I wonder...

Vidar
Title: Re: A Pendulum should really work
Post by: conradelektro on April 08, 2011, 11:27:10 AM
It is obvious that the amperage coming out of a piezo element is very low (because it is an electrostatic effect). Whatever we do, we will not make the piezo effect more powerful in any significant way.

Therefore one has to come up with a "drive" that uses very low power (in the range of ÂµA).

May be I am wrong, but I am aiming at a heavy imbalanced wheel or heavy pendulum which by itself (because its weight overwhelms air drag and friction in the axis bearings) comes almost back to its initial position. The heavy imbalanced wheel would almost complete a revolution and the heavy pendulum would almost complete the same amplitude at each swing. And because it is heavy it will bend the piezo element also at low speed.

And with the microamperes from the piezo elements one could hope to overcome the "almost" if the contraption is carefully built.

The imbalance in the pager motor (which is in itself a nice gadget) is not heavy enough to bend the piezo element when turned slowly. So, one needs Milliamperes to impart speed on the imbalanced wheel of the pager motor which only then gives the necessary "weight" to bend the piezo.

The question can be reduced to: is it possible to overcome the losses (air drag, friction in the bearing) in a heavy imbalanced wheel or a heavy pendulum with Micro-Watts? By "heavy" I am thinking about 1 kilo.

Title: Re: A Pendulum should really work
Post by: Low-Q on April 08, 2011, 02:32:13 PM
I have now ordered 50 pcs 43mm piezo's on ebay. It should do for trial and error. 35 dollars for all 50pcs. It's worth a try.

Regarding heavy imbalanced wheels. They suffer from the very same air drag and friction as any other wheels with same shape. However, if the weight is the main reason why there is applied more force to the piezo, this must be the only, and important, reason why a heavy imbalanced wheel will work better.

I choose a lighter, but probably at least as much efficient design using neodym magnets (Which at most repel and attract with several kg for each small magnet). The short pulses from the passing magnet represent a higher frequency, which in turn will increase the current from an electrostatic unit, and hopefully make it more efficient.

Well, I do not know the outcome yet, but therefor I want to test this out. I also have extracted a bunch of small long neos from brushless RC-motors lately. So I am prepared for some tests :)

Vidar
Title: Re: A Pendulum should really work
Post by: Low-Q on April 08, 2011, 03:17:38 PM
A nice link for those who want to do some research on piezo units:
http://www.americanpiezo.com/knowledge-center.html (http://www.americanpiezo.com/knowledge-center.html)

Vidar
Title: Re: A Pendulum should really work
Post by: lumen on April 08, 2011, 06:20:43 PM
Vidar,
In a rotary design, the RPM could be increased to some resonate frequency for higher gain.

The testing I have done was on a high voltage element for a lighter and the measured compression was only about .001 inch. The disks can deflect further but they don't need much deflection for a large output. I believe this is a workable concept with the main disadvantage that they may fail over time.

Title: Re: A Pendulum should really work
Post by: Low-Q on April 08, 2011, 07:57:38 PM
Vidar,
In a rotary design, the RPM could be increased to some resonate frequency for higher gain.

The testing I have done was on a high voltage element for a lighter and the measured compression was only about .001 inch. The disks can deflect further but they don't need much deflection for a large output. I believe this is a workable concept with the main disadvantage that they may fail over time.
I think that if this works, my guess is that if something fails over time, it will already be covered by the "income" from such a design :)

A little rough, we can say that a modulus of elasticity of a quartz chrystal is about 70 GPa, so that compression of a 1 cm3 chrystal, will at 1 Newton force compress something like 1.4 nanometers. So there is not much compression to talk about.

Increasing the RPM will probably also increase efficiency as the electrostatic properties allows more current as the frequency increase.

Can't wait to try this out.

Vidar
Title: Re: A Pendulum should really work
Post by: Low-Q on April 08, 2011, 09:00:15 PM
A nice demonstration. It isn't much force required to ligt an LED. Ofcourse it doesn't require much energy to power an LED, but what if we apply tens of Newton, several hundered times pr. second? Should it at least be enough to run a small selfrunner?
Title: Re: A Pendulum should really work
Post by: DreamThinkBuild on April 08, 2011, 09:39:00 PM
Hi Low-Q,

I did a test with a piezo speaker through a 1/2 watt 10 ohm resistor.

The values back were between 10mv - 200mv. 200mv was obtained by dropping a 1/2" steel ball bearing on the piezo. This gives a range from low to high of 10uw - 4mw through 10ohms.
Title: Re: A Pendulum should really work
Post by: Low-Q on April 08, 2011, 10:36:39 PM
Hi Low-Q,

I did a test with a piezo speaker through a 1/2 watt 10 ohm resistor.

The values back were between 10mv - 200mv. 200mv was obtained by dropping a 1/2" steel ball bearing on the piezo. This gives a range from low to high of 10uw - 4mw through 10ohms.
That is 4mW in a very short time, but from what altitude did you drop the steel ball from?
The LED in the video above require approx 3V and a few mA. Let's say that piezo generate approx 15mW just by tapping it gently with the fingertip.

Thanks for the info DreamThinkBuild, but I now suddenly realize that the point is however not how many watt you get out, but how the energy are generated. With my preliminary knowledge about piezos, these devices does not provide a counterforce when loaded by a LED or resistor. Yes, they will resist deflection when loaded, but the mechanical interference seems not to disturb or counter the force which is applied to it in a significant way.
This means one can put some kinetic energy into the piezo generator, without actually spending energy to generate this energy, because the kinetic energy you put in seems to be equal to the kinetic energy that bounce back once the piezo has being hit.

Like dropping a steel ball on a polished solid steel plate. It will bounce for quite some time, but the loud high frequency sound it makes at each bounce appearently seems to be "excess" energy - which in a piezo will be electric energy rather than sound.

Vidar
Title: Re: A Pendulum should really work
Post by: DreamThinkBuild on April 08, 2011, 11:07:35 PM
Hi Vidar,

The height drop was around 2" to 3". The piezo was on a wood table so some of the force was dampened. The pulse width is short I didn't take the measurement on the time but it was less then 20msec. I noticed that if you take a small wheel and push it down with a lot of force while running over the piezo, it generates a longer pulse but with a much lower amplitude.
Title: Re: A Pendulum should really work
Post by: Dbowling on April 09, 2011, 12:50:53 AM
Just a thought.
I know Matt Jones has been mighty successful with his bouncer project, getting it to generate electricity. Take a look at it in combination with what you have been discussing here.
In particular, I am thinking about the point on the bouncer that travels up and down, and how that could be made to strike or compress the material you are discussing. Hope that this is worth considering and not a waste of your time.
Title: Re: A Pendulum should really work
Post by: Low-Q on April 09, 2011, 09:38:36 AM
Just a thought.
I know Matt Jones has been mighty successful with his bouncer project, getting it to generate electricity. Take a look at it in combination with what you have been discussing here.
In particular, I am thinking about the point on the bouncer that travels up and down, and how that could be made to strike or compress the material you are discussing. Hope that this is worth considering and not a waste of your time.
The inventor explains that the rotor speeds up when trying to stop the bouncing. The rotor will speed up when you try to stop the bouncing because when it bounce that much, the efficciency are very low due to the non circular movement of the rotating weight. The weight follows then an oval shape which means constantly acceleration and retardation of the weights during each revolution. Stopping the bounce will let the weight follow a circular path and rotate freely. He use this bouncing to generate energy, but this energy is a direct relationship with the energyloss he gets when the machine bounce - also with very low efficiency I would guess.

Taken my preliminary knowledge into account: If he had applied a piezoelectric device, which was fixed to the rig, and also fixed to the table, so no bouncing occoured, he would get the best efficiency and maximum output of the piezo without loosing energy due to bouncing. Only the difference in force applied to the piezo would be the energy source. And a stand still, but yet varying force, does not require energy - because energy are force times distance. If distance are zero, there is no energy input, but still energy output from the piezo due to the difference in applied force.

So, if anyone wants to build a bouncing machine, consider the low efficiency the bouncing applies to the machine. Make it "rock solid", then I believe one can make the most efficient machine.

Vidar
Title: Re: A Pendulum should really work
Post by: Low-Q on April 09, 2011, 09:51:02 AM
Hi Vidar,

The height drop was around 2" to 3". The piezo was on a wood table so some of the force was dampened. The pulse width is short I didn't take the measurement on the time but it was less then 20msec. I noticed that if you take a small wheel and push it down with a lot of force while running over the piezo, it generates a longer pulse but with a much lower amplitude.
I did read this post once more, and realized you got a very good idea! Imagine a ball bearing-like rotor with spring loaded balls or small wheels which is pushed outward to the outer ring. Inside this outer ring we apply an array of piezos, and thet those piezos be the surface for the balls to roll on. If the surface are very smooth, the rolls would roll freely even if they applies great force to the piezos. Then the energy we get out from the piezos can run a small brushless motor which rotate the rotor... What do you think?

Vidar
Title: Re: A Pendulum should really work
Post by: Dbowling on April 09, 2011, 07:47:39 PM
I think if you talked to Matt about the bouncer, you would be very surprised by the energy it produces. I have met with him in person, and have been following his progress for a while. He is not the only one going down this path. I don't believe he would claim overunity, but he gets quite a bit from the coil collapse and the unusual rotation doesn't use as much energy as a standard rotating wheel, from what I understand. I could be wrong. With the addition of the voltage produced by piezos, it might be very interesting. I am going to mention it to him as well.
Title: Re: A Pendulum should really work
Post by: Low-Q on April 09, 2011, 08:39:50 PM
I think if you talked to Matt about the bouncer, you would be very surprised by the energy it produces. I have met with him in person, and have been following his progress for a while. He is not the only one going down this path. I don't believe he would claim overunity, but he gets quite a bit from the coil collapse and the unusual rotation doesn't use as much energy as a standard rotating wheel, from what I understand. I could be wrong. With the addition of the voltage produced by piezos, it might be very interesting. I am going to mention it to him as well.
I would think that a "standard" rotary generator found in most power plants are still the most efficient, most maintenance free, with respect to the energy input requirements - wind, waterfall, waves, steam etc.
But making energy by applying force alone seems to be more interesting since there is allmost no deformation in a chrystal when force are applied - as mentioned 1N force on a 1cm^3 quartz chrystal compress it by approx 1.4nm. Imagine a piezotransducer with 0.2mm thickness and 1cm^2, and apply 1000N of force, the compression is not more than 0.28um (Which is 1000N x 0.28um = 0.28mJ), but the energy output is capable of more than 0.28mJ. So I think it is a good idea to mention the piezoelectric devices to your friend. Let him leave the bouncing machine, and go for a more "silent" generator :)
Title: Re: A Pendulum should really work
Post by: DreamThinkBuild on April 14, 2011, 04:09:12 AM
Hi Vidar,

I missed this, I don't seem to always get notification that a topic has been replied to.

Quote
Then the energy we get out from the piezos can run a small brush-less motor which rotate the rotor

It might be possible with a more powerful piezo element. That would be a good idea hook the piezo up to it's own pulse coil to push itself from a fixed magnet to the next piezo element. A piezo pulse motor.

I'm getting low voltage when rolling, it could be also the piezo speaker I'm using is low quality also. I hooked it to a LED and wasn't able to light it by hitting on the piezo with a small tack hammer.  :)
Title: Re: A Pendulum should really work
Post by: conradelektro on April 14, 2011, 12:25:51 PM
It might be possible with a more powerful piezo element.

I am in the middle of building a hybrid of a pendulum and an imbalanced wheel (it is a pendulum when you do not drive it over 360Â°), and I did some tests and some reading about piezo elements:

---  There are no "powerful piezo elements", we are always getting only ÂµWatts. ---

What I try is to stack many piezo elements and to use their combined output (see the circuit with the many diodes further up in this thread).

But I found that stacking has its limits, because the "mechanical pulse" that made the top element in the stack create some electricity becomes weaker when travelling down the stack. (The piezo elements themselves dampen the hit on the top one.)

May be three elements in a stack is still a useful setup, therefore I want to use many "three element stacks". I am not sure yet, whether stacking is really helping, may be many single-piezo-elements is the better strategy? The trick is to distribute a "hit" over many piezo elements.

First of all I want to come up with a drive for the pendulum/wheel that needs only Microwatts, which might not be possible. I hope that "gravity assists" and that the drive only has to overcome friction in the single bearing and air drag.

The people who built "Bedini Pendulums" needed many Milliwatts (about a thousand times more than I intend to use).

So, first a very low power drive and then many three-piezo-element-stacks or many single-piezo-elements.

P.S.: At least I get a very low power pendulum out of it (a device to calm your nerves or to drive you crazy, whatever your mental disposition).
Title: Re: A Pendulum should really work
Post by: onthecuttingedge2010 on April 14, 2011, 10:16:47 PM
what you want is a large surface area Piezoelectric flat transducer, not stacked. just volume. if you could make your own you could make some pretty big ones with good surface volume. surface area is very important here.
Title: Re: A Pendulum should really work
Post by: onthecuttingedge2010 on April 14, 2011, 10:57:22 PM
can you imagine a Piezoelectric Transducer the size of a big Gong?
Title: Re: A Pendulum should really work
Post by: onthecuttingedge2010 on April 15, 2011, 02:09:57 AM
If this was a piezoelectric transducer you would have some very excellent results and tons of fun on top of things.

a little tap and it will sing its self into energy mayhem.

I shall always be the first to find it and the last, no matter if they use time to take advantage of it.

it is like the roar of a lion and flows like living waters.

I am simply showing you a direction, nothing more.

I know power when I hear it.

Jerry 8)
Title: Re: A Pendulum should really work
Post by: DreamThinkBuild on April 15, 2011, 02:45:22 AM
Hi Jerry,

Nice gong.

The biggest I could find is a 2.5" diameter disk, they are pretty expensive.

http://www.piezo.com/prodsheet3disk5A.html

Might need a whole lot of them to cover that sized gong. :)

When searching for disk I stumbled on Piezo Cable. I wonder how that would work for swinging the pendulum.

http://www.meas-spec.com/product/t_product.aspx?id=2476
Title: Re: A Pendulum should really work
Post by: onthecuttingedge2010 on April 15, 2011, 02:51:22 AM
Hi Jerry,

Nice gong.

The biggest I could find is a 2.5" diameter disk, they are pretty expensive.

http://www.piezo.com/prodsheet3disk5A.html

Might need a whole lot of them to cover that sized gong. :)

When searching for disk I stumbled on Piezo Cable. I wonder how that would work for swinging the pendulum.

http://www.meas-spec.com/product/t_product.aspx?id=2476

I am afraid you will have to learn to make them yourself to your specifications unless you are very rich. if you are rich then please disregard this post. learn to make Piezoelectric materials yourself, this is my target and should be your target.

Jerry 8)
Title: Re: A Pendulum should really work
Post by: onthecuttingedge2010 on April 15, 2011, 03:15:56 AM
The race is on. starting now. I wish you the best of luck! and may your god be with you. I will see you all at the finish line. cheers.
Title: Re: A Pendulum should really work
Post by: DreamThinkBuild on April 15, 2011, 03:36:43 AM
Hi Jerry,

Quote
if you are rich then please disregard this post

LOL, rich in ideas, but not in the wallet. :)

I found this video on how to make piezo crystals.

http://blog.makezine.com/archive/2011/03/collins-lab-homebrew-piezo.html