Wire connectiions and rotating platforms

[Robotboy86]

I have always kinda wondered how engeers design a system that lets a top peice rotate, but still send signals through wires to below.  THe bottom peice is stationary though.  The wires would naturally get twisted.. the only way I could see of getting around that is to have a wire connection that is a cylinder and let a wire connect to the cylinder that could then spin inside of the sensor or what have you..  that wouldlet the wiring stay stationary.



...How do they do it? Sorry if its not well explained.. but its kind of difficult to put into words right now

[paulstreats]

this isnt easy to do, It is rare that you would see a continuous rotating platform that could send signals. These days you could probably use a wireless transfer system like blue tooth if you really wanted.
Also you could produce a system like a standard motor uses, the wires brush against connections on the central rotating shaft to provide it with power.

[paulstreats]

ooo
and if the platform could have a small power source itself, you could also use ir to transfer data signals

[awally88]

I worked building wind turbines for a couple of months after leaving high school, they have a lot of electrical wiring going from the top to the bottom and the top (nacelle) will move to the direction the wind is going.  The way they get around this (As running electricity cannot use wireless[yet]) is the nacelle will only turn a certain amount of times before it stops and rotates the opposite direction to get to the correct position. 

With a robot you could do this, running your wires through a cylinder, as long as you made sure you had enough slack cable for the robot to spin to the maximum displacement.

I hope this helps,
Awally88

[Ro-Bot-X]

Build a PCB with as many circular traces as so many wires you need to go through. Then on a rectangular piece solder same number of flexible metal blades spaced so they will touch the circular traces like an old pick-up record player arm... Make sure you add some non conductive grease for easy rotation.

[Nyx]

Build a PCB with as many circular traces as so many wires you need to go through. Then on a rectangular piece solder same number of flexible metal blades spaced so they will touch the circular traces like an old pick-up record player arm... Make sure you add some non conductive grease for easy rotation.

The problem with that is, while it will work for conducting power, for any kind of information transfer, it won't work well, because the contact will be lost at different points in the rotation... Now if you use a digital signal, you *may* be able to have an error correction scheme that can recover from it, but even then, that's a maybe. The other problem is that no matter what, the friction will end up damaging the contacts.

It depends on what you want, but as a previous poster mentioned, it's simpler if you just restrict the rotation... Think of a human torso... You can rotate so many degrees left, so many degrees right, but you can't do a complete rotation, unless you're possessed of course.

[Robotboy86]

thanks guys

How do they do the radar thing on top of boats then???

[paulstreats]

thanks guys

How do they do the radar thing on top of boats then???

The actual spinning part is called a radar scanner. This has relatively no technology built into it.

The actual radar emitter is stationary allowing it to be wired to as normal, the scanner part spins around it (THIs is usually nothing more than a mirror which reflects the radar waves in whichever direction it is facing, because it is a mirror, radio waves reflect just like light waves (they are in the same spectrum)  and therefore cannot travel through the back of the mirror.

The radar detector doesnt actually need to be focused in any way as the only waves that are available for it to pick up are obviously coming from the direction the mirror was pointing. This is why radar jammers can be used.

so the detector part isnt necesarily focused by the mirror

[paulstreats]

an easier way to think about the above is an old light house, there is a stationary light bulb and a mirror directs the light.(ALSO used in police car lights etc..)

[Robotboy86]

Thanks guys! I always wondered

[airman00]

or maybe you could do wireless electricity...

basically you would transmit electricity from coil to coil. Exactly like a transformer works, except one coil would spin on a motor and the other would provide it with energy.

I think some toothbrushes use that..

[crossroads1946]

some hi-tech slip rings: http://www.mercotac.com/html/products.html

A similar question on google: http://answers.google.com/answers/threadview?id=705769

Baker

[airman00]

cool stuff
anybody ever use my idea about the transformer?

[awally88]

anybody ever use my idea about the transformer?

Wi-Tricity, I heard about it in the paper a few months ago, allegedly they can light a 60Watt light globe from across the room!! They use EM waves to transmit the power across around 2 or 3 metres. Technology is awesome!

Also I think Tesla tried doing something like this as well if I'm remembering correctly..
Awally88

[crossroads1946]

There are a couple different ways of "transmitting" electricity wirelessly. One is based on flux - the same principle that charges those flashlights that you shake; the change in magnetic field induces a current through a coil of wire. In the case of the electric toothbrush that doesn't use electrical connections to charge, there is a change in electric field in the base, caused by the AC current from the house circuit, which induces a current in the coils in the brush.

There are other methods as well based on tried and true physics... far from new technology. We did the lighting a bulb from several meters away demonstration in my physics class all the time. Tesla was planning on powering cities with it: http://www.world-mysteries.com/doug_teslat.htm (granted, very biased, but interesting none-the-less), http://www.reformation.org/tesla-wireless-transmission.html, and http://www.pbs.org/tesla/ll/ll_todre.html. There are new technologies that are coming out that use the same principles as well. You can get a full run-down at http://en.wikipedia.org/wiki/Wireless_energy_transfer.

Baker

[paulstreats]

i always enjoy reading about nikola tesla

[HDL_CinC_Dragon]

http://www.world-mysteries.com/doug_teslat.htm

After reading nearly this entire page minus the last 3 or 4 paragraphs, I have drawn some conclusions:
1) Nikola was the most badass guy to ever walk this earth and I feel bad about not researching him before
2) Humans suck

[airman00]

Interesting article..

But why did no one try to improve on Tesla. Why hasn't anyone try to build a working replica of that tower?

[paulstreats]

the same reason that were all still using fossil fuels in our cars.

its all economy that makes the world go round unfortunately, and also the economy that dictates which technology gets used, if electricity were free than there would be no economical gain from it, therefore less money (either in tax or directly) for governments to use.

[HDL_CinC_Dragon]

So whats to stop some privately funded individual from building a tower and using it to power up a building to show the world what it can do?

thought:
Governments spend MILLIONS of dollars on environmental stuff (except china... jerks) why not just build these towers all over the country and get rid of all other power plants except maybe the solar and wind ones so that way instead of losing millions a year to fight our own assets, we can just do way with the problem and have free energy for all!!... Does anyone want to go take over a small country with me, make it our own, and then show the world how much it sucks by being the most awesome and technically advanced society ever before imagined?

Im probably not seeing some politics here...

[airman00]

Thats true, why hasn't any private company built it.

Also we are not exactly sure that it works. And maybe if it worked it would generate so little electricity that it would not be worth it. Imagine a huge 200 ft tower that generates 12 Volts @ 25 mA.

But hey, if it would work that would mean free electricity!
Cmon wont anyone build this?

[crossroads1946]

Efficiency and cost are the key issues here.

First off, there is no such thing as free energy... That article made no mention about the source of the electricity to be transmitted wirelessly; simply the broadcasting and receiving of it. There still had to be a source before it could be transmitted. The cost of this source energy would actually be greater than if everyone simply tapped into the source through a wired system (for efficiency reasons, described next).

The efficiency of such a wireless transmission is extremely low. The total amount of electricity that can be drawn from the tower has to be less than (or in perfect conditions, equal to) the amount of power that goes into the tower from the source. Since the EM waves from the tower are broadcast in all directions, most of the energy will be lost. You can think of this in similar terms of a flashlight bulb. If you're trying to light up an object, you can aim  the flashlight at the object so that most of the light goes towards that object. It would be far less efficient to take the bulb out of it's reflector so that it light's up the whole room. Light goes everywhere, but as a result, it is much dimmer, and most of it does not even touch the object you're trying to see. The same goes for EM waves, in this case the wireless electricity. Omni-directional broadcast is much less efficient than directional broadcast, which is far, far, less efficient than a direct link from hard-wired.

The reason wireless power transmission was even considered back in Tesla's time was because there was no major infrastructure in place for wired power lines. They didn't already have wires and power lines run everywhere you can imagine, mostly because before Tesla himself invented Alternating Current, it was very difficult to send direct current on wires for long distances. Also, wire was still expensive and more difficult to manufacture than it was in later years. By using wireless power transmission, they could get around having to design and implement a massive infrastructure that would be very expensive to build.

After AC took root, the infrastructures were implemented, and wire and insulator technology was improved, wired electricity was far more efficient than the wireless alternative.

Baker

[paulstreats]

So whats to stop some privately funded individual from building a tower and using it to power up a building to show the world what it can do?

thought:
Governments spend MILLIONS of dollars on environmental stuff (except china... jerks) why not just build these towers all over the country and get rid of all other power plants except maybe the solar and wind ones so that way instead of losing millions a year to fight our own assets, we can just do way with the problem and have free energy for all!!... Does anyone want to go take over a small country with me, make it our own, and then show the world how much it sucks by being the most awesome and technically advanced society ever before imagined?

Im probably not seeing some politics here...

unfortunately what happens is exploitation.

most governments now are "EnErgy efficient" what they do is get their citizens to buy en3ergy efficient bulbs from countries like china.
Those bulbs manufacture take far more energy than a normal light bulb i.e. sourcing materials, making the plastics, transport etc.. what then happens is we use less energy in our country by using the product, but the country that made the product(china) has greater energy usage. its really just pinching from peter to pay paul
I read a report last year explaining this and also something similar with wind farms in that the energy they create in the life time of running is something similar to the energy it costs to manufacture them?

just some countries dont really care, and some countries would rather pass the buck than actually save energy and therefore money.

[airman00]

I know it wasnt really "free energy". The tower was supposed to use the energy that the earth created by spinning.
Im not sure about the exact details but it had to do something with harnessing the power of the earth revolving.

The wireless transmission was terribly inefficient ( yet cool) but the tower used the earth as "the source"

[HDL_CinC_Dragon]

Ah I forgot to say:
I wasnt referring to the wireless transmission of power. We dont need that. We can just wire everything... most countries already have the wire infrastructure needed. All I care about is the clean energy and such... im a BIIIIG proponent on clean energy...