A Pendulum should really work

[conradelektro]

@gyulasun and elgersmad:

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?

Greetings, Conrad

[elgersmad]

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:
YouTube Video

Slow works

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

This is a link.
Super Solenoid

Needs more grease.

[conradelektro]

@elgersmad: A question

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?

Greetings, Conrad

[elgersmad]

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.

[conradelektro]

I read a bit about piezo materials:

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 100µW (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).

Greetings, Conrad