A piezo crystal will develope a voltage across its surfaces if a physical pressure is applied to it.

If a load (say a LED) is connected to the voltage source, will a current continue to flow as long as pressure is applied ?

rumpole said:

A piezo crystal will develope a voltage across its surfaces if a physical pressure is applied to it.

If a load (say a LED) is connected to the voltage source, will a current continue to flow as long as pressure is applied ?

no its a change in pressure rather than a consistent pressure

rumpole said:

A piezo crystal will develope a voltage across its surfaces if a physical pressure is applied to it.

If a load (say a LED) is connected to the voltage source, will a current continue to flow as long as pressure is applied ?

No. It is physical deformation of the crystal, not the pressure that causes the electric discharge.

I’m told that if you crush sugar granules in the dark that you’ll see flashes of light

if you pushed a hammer onto a crystal you’ll generate a voltage but if you held that hammer on the crystal with consistent force the crystal generates no voltage

Carmen_Sandiego said:

rumpole said:

A piezo crystal will develope a voltage across its surfaces if a physical pressure is applied to it.

If a load (say a LED) is connected to the voltage source, will a current continue to flow as long as pressure is applied ?

No. It is physical deformation of the crystal, not the pressure that causes the electric discharge.

I’d assume that its the pressure you apply that cause the deformation

its why some people have had the idea of making roads of crystals to generate electricity, the passing car creates the force/ pressure on the crystal that generates a voltage (4/5ths of fuck all). its an impractical idea.

microphones use the changes in air pressure to apply a force to the crystal to generate a tiny voltage, that voltage gets amplified and can then be used by a black box to amplify your voice (the amplitude of the original source)

So can we say the situation is analogous to applying pressure to a hydraulic piston, ie the oil (current), only flows while the piston (crystal) is moving (being deformed) ?

rumpole said:

So can we say the situation is analogous to applying pressure to a hydraulic piston, ie the oil (current), only flows while the piston (crystal) is moving (being deformed) ?

Yes, that is lose. It also has the benefit of also working with the process in reverse – push oil in reverse and the piston moves. (which is the role the ‘quartz crystal’ plays in digital watches)

if you viewed the crystal as having capacitance (just an example, I haven’t checked the R, L and C – the Z) then the deformed capacitance might be different, so it could be used as a strain sensor, connected with a circuit to an LED. So yeah you have the small voltages that might be generated by change, and you have the Impedance changes of some deformed state.

Wild guess.

can’t see what I’m doing here, no glasses on

http://en.wikipedia.org/wiki/Piezoresistive_effect

The piezoresistive effect is a change in the electrical resistivity of a semiconductor or metal when mechanical strain is applied. In contrast to the piezoelectric effect, the piezoresistive effect causes a change only in electrical resistance, not in electric potential.

The change of electrical resistance in metal devices due to an applied mechanical load was first discovered in 1856 by Lord Kelvin. With single crystal silicon becoming the material of choice for the design of analog and digital circuits, the large piezoresistive effect in silicon and germanium was first discovered in 1954 (Smith 1954).

http://en.wikipedia.org/wiki/Piezoelectric

Piezoelectricity /piˌeɪzoʊˌilɛkˈtrɪsɪti/ is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure. It is derived from the Greek piezo or piezein (πιέζειν), which means to squeeze or press, and electric or electron (ήλεκτρον), which means amber, an ancient source of electric charge. Piezoelectricity was discovered in 1880 by French physicists Jacques and Pierre Curie.

I agree with all the above.

I find it amusing that Pierre Curie’s discovery of piezoelectricity was an essential prerequisite to his wife Marie Curie’s discovery of polonium and radium. Applying pressure to a piezoelectric crystal generated a voltage difference between a pair of electrodes, and the ionizing effect of the particles given off by the radioactivity allowed that voltage to drain away from one electrode to the other. By measuring the rate at which the voltage dropped, Marie Curie for the first time measured the strength of radioactivity.

So the minimum needed to measure the strength of radioactivity is a piezoelectric crystal, a weight to stress it, and a leaf electroscope .

rumpole said:

So can we say the situation is analogous to applying pressure to a hydraulic piston, ie the oil (current), only flows while the piston (crystal) is moving (being deformed) ?

As DO said, that’s a reasonable analogy. The Wikipedia article has a diagram:
Wikipedia said:

A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)

…

wookiemeister said:

its why some people have had the idea of making roads of crystals to generate electricity, the passing car creates the force/ pressure on the crystal that generates a voltage (4/5ths of fuck all). its an impractical idea.

microphones use the changes in air pressure to apply a force to the crystal to generate a tiny voltage, that voltage gets amplified and can then be used by a black box to amplify your voice (the amplitude of the original source)

No, Wookie. The voltage isn’t 4/5ths of fuck all. Depending on the crystal, the voltage can be quite high. The amount of current coming out of a small crystal may be fairly small, though, especially if the stress it’s subjected to is small (eg, sound vibrations traveling through the air).
Wikipedia said:

For example, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 V.

That high voltage can be handy for some applications, eg piezoelectric gas lighters. Fortunately, the voltage depends on the chemical type of the crystal, its size, the strength of the applied force, and the direction of the applied force relative to the crystal structure, so it’s fairly easy to make low voltage crystals.

…

The amount of electrical energy that comes out of a piezoelectric crystal depends on how much mechanical energy you can push into it. There are some losses, due to the mechanical vibration being converted into heat rather than electric current, but as transducers go, they’re pretty efficient.

As the diagram above illustrates, you have to keep deforming the crystal to get electrical energy out of it. A static deformation of the crystal will induce electrical polarization and hence a voltage difference across the crystal, but a static deformation does no work, so no current will flow. So if you just sit a weight on top of a piezoelectric crystal you’ll get an initial current flow as the crystal is being deformed, but once the crystal has settled into its new configuration, no more current will flow. But since the static pressure affects the piezoelectric crystal’s electrical characteristics, if you put it into a circuit that supplies it with current it can be used as a static pressure sensor.

Some pages with images showing different types of quartz crystal cuts.
http://txccrystal.com/term.html
http://www.hoorayhk.com/index.php?c=crystal
http://www.modalshop.com/calibration.asp?ID=176

I must say, I’m sceptical about proposals to generate significant electrical power from deformations caused by vehicles. If the road has to be made more deformable then we are just getting power from the road at the expense of lower efficiency of the vehicle.

On the other hand, where there are significant deflections anyway, such as in bridges, it may be that some energy can be extracted without reducing the efficiency of the vehicles. It wouldn’t be a huge amount though; some small % of the energy generated by the vehicle engines as they cross the bridge.

PM 2Ring said:

rumpole said:

So can we say the situation is analogous to applying pressure to a hydraulic piston, ie the oil (current), only flows while the piston (crystal) is moving (being deformed) ?

As DO said, that’s a reasonable analogy. The Wikipedia article has a diagram:
Wikipedia said:

A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)

…

wookiemeister said:

its why some people have had the idea of making roads of crystals to generate electricity, the passing car creates the force/ pressure on the crystal that generates a voltage (4/5ths of fuck all). its an impractical idea.

microphones use the changes in air pressure to apply a force to the crystal to generate a tiny voltage, that voltage gets amplified and can then be used by a black box to amplify your voice (the amplitude of the original source)

No, Wookie. The voltage isn’t 4/5ths of fuck all. Depending on the crystal, the voltage can be quite high. The amount of current coming out of a small crystal may be fairly small, though, especially if the stress it’s subjected to is small (eg, sound vibrations traveling through the air).
Wikipedia said:

For example, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 V.

That high voltage can be handy for some applications, eg piezoelectric gas lighters. Fortunately, the voltage depends on the chemical type of the crystal, its size, the strength of the applied force, and the direction of the applied force relative to the crystal structure, so it’s fairly easy to make low voltage crystals.

…

The amount of electrical energy that comes out of a piezoelectric crystal depends on how much mechanical energy you can push into it. There are some losses, due to the mechanical vibration being converted into heat rather than electric current, but as transducers go, they’re pretty efficient.

As the diagram above illustrates, you have to keep deforming the crystal to get electrical energy out of it. A static deformation of the crystal will induce electrical polarization and hence a voltage difference across the crystal, but a static deformation does no work, so no current will flow. So if you just sit a weight on top of a piezoelectric crystal you’ll get an initial current flow as the crystal is being deformed, but once the crystal has settled into its new configuration, no more current will flow. But since the static pressure affects the piezoelectric crystal’s electrical characteristics, if you put it into a circuit that supplies it with current it can be used as a static pressure sensor.

Got my wires crossed in that post

The power output is (4/5 ths ) of fuck all

Piezos are mainly used as sensors for a very good reason

As we build roads that don’t last there’s little point laying down piezos

>I must say, I’m sceptical about proposals to generate significant electrical power from deformations caused by vehicles. If the road has to be made more deformable then we are just getting power from the road at the expense of lower efficiency of the vehicle.

Not much power to be had that way, I prefer rollers on the road with electric motors, that slow motorists down and keep their acceleration at safe levels. Sort of absorbs peoples’ excesses. Also braking can be slightly adjusted this way, absorbing some of that energy too. A win win situation.

:) love these moments of genius, keep in mind you read of it here first.

wookiemeister said:

As we build roads that don’t last there’s little point laying down piezos

Do you?

Maybe you should leave it to the people who build roads that do last.

I have a sneaking BBQ lighters that produce the spark use the piezo method

The voltage must be high enough to jump the small gap

The Rev Dodgson said:

wookiemeister said:

As we build roads that don’t last there’s little point laying down piezos

Do you?

Maybe you should leave it to the people who build roads that do last.

The Romans

Everyone else is a wanna be

They can’t and won’t build long lasting roads here

I got talking to a bloke that seemed too know lots about road building

1 to build a proper road that will stand the test of time you have to go back to building like the Romans . Dig down 1.5 m lay down matting and fill with rocks largest at bottom , smallest at top.

2 the matting or otherwise needs to keep the sides if the road from spreading out, when this happens the road starts falling apart

3 you lay down concrete ( as a cap I think I remember he said)

4 stop sabotage – the road builders will sabotage the road because they’ve money from digging it up every decade or so. The Romans would have just executed such people.

wookiemeister said:

The Rev Dodgson said:

wookiemeister said:

As we build roads that don’t last there’s little point laying down piezos

Do you?

Maybe you should leave it to the people who build roads that do last.

The Romans

Everyone else is a wanna be

They can’t and won’t build long lasting roads here

The Romans did alright for the time, but their roads wouldn’t last 5 minutes under today’s traffic.

A typical main road pavement would last much longer than a typical piezoelectric crystal, so amongst the many good reasons why generating electricity this way is not a good idea, short road life is not included.

wookiemeister said:

I got talking to a bloke that seemed too know lots about road building

1 to build a proper road that will stand the test of time you have to go back to building like the Romans . Dig down 1.5 m lay down matting and fill with rocks largest at bottom , smallest at top.

2 the matting or otherwise needs to keep the sides if the road from spreading out, when this happens the road starts falling apart

3 you lay down concrete ( as a cap I think I remember he said)

4 stop sabotage – the road builders will sabotage the road because they’ve money from digging it up every decade or so. The Romans would have just executed such people.

1. That isn’t how the Romans built their roads.

2. That is how modern roads are built, where required, which it usuall isn’t.

3. Your point 4 is pure wookie crap.

The Rev Dodgson said:

wookiemeister said:

I got talking to a bloke that seemed too know lots about road building

1 to build a proper road that will stand the test of time you have to go back to building like the Romans . Dig down 1.5 m lay down matting and fill with rocks largest at bottom , smallest at top.

2 the matting or otherwise needs to keep the sides if the road from spreading out, when this happens the road starts falling apart

3 you lay down concrete ( as a cap I think I remember he said)

4 stop sabotage – the road builders will sabotage the road because they’ve money from digging it up every decade or so. The Romans would have just executed such people.

1. That isn’t how the Romans built their roads.

2. That is how modern roads are built, where required, which it usuall isn’t.

3. Your point 4 is pure wookie crap.

Even children’s book show this method of construction

Trench, matting, stones piled up inside going from large to small with fillers between the large rocks. The paving must have been the capping.

Most of the roads over here are fucked because they either don’t know how to build them or won’t pay for the proper job.

I have met some council bloke who pointed at a pristine asphalt surface and told me proudly that in seven years time that this minor residential road would all be ripped up and resurfaced again. I shook my head.

Another road in the area must have had one if these luminaries living on the road too, they tore up a few kilometres of road that every resident agreed should have never been touched

University of Twente

Generating electricity from vibrations in road surface works

21 February 2012

In the autumn of 2011, a piezoelectric material that converts vibrations from passing vehicles into energy was applied to the surface of the N34 motorway. The piezoelectric material was applied to the road surface in a rural area where the speed limit is 100 km per hour. The aim of the pilot project was to investigate the feasibility of piezo technology in road construction. The research was carried out by the Tauw advice and engineering agency and the University of Twente in partnership with the Dutch province of Overijssel.

The aim of the pilot project was to establish whether electrical energy can be generated from traffic vibrations using piezoelectric material and, if so, how much energy can be generated. The trial system was tested in various weather conditions between October and December 2011. A measurement device was used to continually monitor the system and collect data.

Results

Tauw and the University of Twente have concluded that energy can indeed be generated using piezoelectric material in the road surface. The amount of energy generated depends on the number of passing vehicles and the number of piezo elements in the road. Vehicles that are moving more slowly appear to generate slightly more energy than faster-moving vehicles, but further research is needed to confirm this.

The amount of energy generated during the pilot project was too small to be used for traffic lights or street lighting, but it was enough for devices that need less energy, such as wireless motion sensors, which detect vehicles and send a signal to, for example, traffic lights. Currently these are mainly powered by batteries or solar panels. Vibration energy is a sustainable alternative for these power sources.

The project partners also concluded that integrating piezo elements in an existing road surface is problematic. For the pilot research, a narrow groove was cut into the road and a steel housing containing the piezo elements was fitted into it. Ultimately it turned out that the housing was not strong enough to withstand the forces of the passing traffic, and it came loose in December. This did not cause a traffic hazard, but it did mean that the research ended a few weeks earlier than planned.

Applications

The project partners are hopeful about other applications. Project leader Simon Bos says: “The application of vibration energy in existing roads did turn out to be difficult, but we do see possibilities for existing and new bridges and viaducts, for example at expansion joints. Of course further research into a good, strong design has to be carried out before this can be applied on a large scale.”

Next steps

Following the pilot project, various interested parties have contacted Tauw and the University of Twente to carry out further research into vibration energy. Piezo elements can not only be fitted under bridges and viaducts, but also under concrete road slabs and speed bumps, or alongside railway lines or water drainage channels. The application of piezo elements beneath concrete slabs is at an advanced stage, while the other possible applications are still in the research phase.

END OF PRESS RELEASE

Try here, rather than kid’s books:

http://en.wikipedia.org/wiki/Roman_roads

Roman construction is normally very good though I have come across a few places where some shoddy methods and bad location have limited the build to perhaps 1500 years practical use

wookiemeister said:

Most of the roads over here are fucked because they either don’t know how to build them or won’t pay for the proper job.

Good to see the good old cultural cringe is alive and well.

but didn’t roman roads get ruts in them from wagon wheel which lead to the width of the space shuttle being two asses arses wide?

If you believe that laying piezos in the roads will generate any useable energy , you might be very interested in my “ shout your way to weight loss” programme

ChrispenEvan said:

but didn’t roman roads get ruts in them from wagon wheel which lead to the width of the space shuttle being two asses arses wide?

I’ve heard it was horses arses that designed Sydney’s CBD road network

Well really it was just horsing choosing the route to go from A to B, the wagon driver allowed them some leeway which led to the spider on caffeine spiders web of roads

There is only one road in Sydney that FOLLOWS the contour of the land – edgecliffe road.

Every other road is forced up dangerous inclines – have a look at randwick coogee area

Brainless

Normally you run a series of roads along the contours of hills

It makes more efficient use of land for housing and allows safer passage of travellers

From the main Innowattech page:

Innowattech is an R&D company based at the Technion, Haifa Israel. It has developed unique patented piezoelectric generators which harvests the mechanical energy imparted to railways, roadways and pedestrian ways from passing traffic which is usually dissipated as wasted heat and converts it into green electricity. The system is especially suited for supplying electricity for specific needs in remote sites which are far from the electrical grid.

Technical Information – The piezoelectric generators do not steal energy from passing vehicles because their Young’s modulus is greater than that of the roadway or railway

From http://www.innowattech.co.il/events.aspx

October 2009

The technology developed by Haifa-based Innowattech Ltd. was recently tested in a complete-system pilot project along a ten-meter stretch of Road 4 north of Hadera, Israel.

This is the first practical test of the innovative green energy technology developed by Innowattech, in association with Technion I.I.T (Israel Institute of Technology). The pilot is being conducted in cooperation with the Israel National Roads Company.

The technology is based on piezoelectric materials that enable the conversion of mechanical energy exerted by the weight of passing vehicles into electrical energy.

The first of its kind project demonstrated how Israeli technology can generate electricity from generators installed beneath a road’s asphalt layer, presenting a pioneering invention for “parasitic energy harvesting.” The technology does not increase the vehicles’ fuel intake or affect the road infrastructure, harvesting the energy, which would have otherwise been wasted on road deformation, rendering this energy as “parasitic.”

The system developed by Innowattech includes IPEGs™ (Innowattech Piezoelectric Generators), a harvesting module and a battery charging mechanism. During the pilot, the IPEGs™ were placed at a depth of five centimeters beneath the road’s upper asphalt layer on a stretch of ten meters, capable of producing some 2,000 watt-hours (Wh) of power per hour on average on that stretch. The harvested power is relayed via a harvesting module to a battery charging mechanism beside the road.

Expanding the project to a length of one kilometer along a single lane would be capable of producing an average of 200 KWh per hour, sufficient electricity to provide for the average consumption in 200-300 households, provided approximately 600 heavy trucks or buses travel through the interval per hour on average.

That sounds promising (although I wouldn’t like to live next to a road that gets 10 heavy vehicles per minute), but note that recent Innowattech projects appear to concentrate on powering sensors, eg a self-powered weigh-bridge, rather than bulk energy production…

They could always use something like a solar panel to generate power for a weigh bridge I guess

wookiemeister said:

There is only one road in Sydney that FOLLOWS the contour of the land – edgecliffe road.

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

PM 2Ring said:

wookiemeister said:

There is only one road in Sydney that FOLLOWS the contour of the land – edgecliffe road.

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

In fact almost every suburb in NE Sydney is built on ridges in between deep valleys, with roads largely following the contours.

PM 2Ring said:

wookiemeister said:

There is only one road in Sydney that FOLLOWS the contour of the land – edgecliffe road.

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

Still quite an incline there they might have been better off cutting through the hill for the road

The Rev Dodgson said:

PM 2Ring said:

wookiemeister said:

There is only one road in Sydney that FOLLOWS the contour of the land – edgecliffe road.

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

In fact almost every suburb in NE Sydney is built on ridges in between deep valleys, with roads largely following the contours.

Like Arden street ?

wookiemeister said:

The Rev Dodgson said:

PM 2Ring said:

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

In fact almost every suburb in NE Sydney is built on ridges in between deep valleys, with roads largely following the contours.

Like Arden street ?

Actually Arden at is coogee way

The road up from manly is very steep

wookiemeister said:

PM 2Ring said:

wookiemeister said:

There is only one road in Sydney that FOLLOWS the contour of the land – edgecliffe road.

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

Still quite an incline there they might have been better off cutting through the hill for the road

What hill? The ridge that King St follows is fairly level until it gets to Newtown railway station; the only incline is the stretch from there to St Peters.

PM 2Ring said:

wookiemeister said:

PM 2Ring said:

I suspect that it’s not the only one… Eg, King St, Newtown (which starts at Broadway, goes past Sydney University, through Newtown, and thence to St Peters, where it becomes the Princes Hwy), follows the contour closely, and is fairly level until it gets to Newtown railway station.

Still quite an incline there they might have been better off cutting through the hill for the road

What hill? The ridge that King St follows is fairly level until it gets to Newtown railway station; the only incline is the stretch from there to St Peters.

Go west from the overpass at the uni and that is a significant incline

>Go west from the overpass at the uni and that is a significant incline

just past the piezoelectric derailment

transition said:

>Go west from the overpass at the uni and that is a significant incline

just past the piezoelectric derailment

OMG there’s piezos everywhere