# Wireless Power

## Step 7: Extra Hardware

I have now added a AC to DC diode bridge which converts AC to DC. Then i added a Joule Theif to the diode bridge, which is a very simple circuit that can amplify input power (the Dc voltage from the diode bridge). http://www.youtube.com/watch?v=gTAqGKt64WM

This allows the LED to be lit when its father away from the coil, because the voltage going to the LED is higher. It is now able to power DC devices.

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are_pit2 years ago
hello guys...
i'am want to know...
how the secondary receive volt from primary...
can u explain to me....
thanks you..
2 years ago
There are a couple of things you should know before I begin to explain how this works.

Firstly, when electricity runs though anything (not just wires) it creates a very very very small electromagnetic field.

Secondly, this electromagnetic field has a spin around the conductor relative to the direction of flow of electricity.*

Thirdly, this spin is amplified by proximity to other conductors.

Fourthly, flow creates spin and spin creates flow.

Now that you know those four things I can begin to explain.

The primary coil is a coil and not just a solitary wire because the voltage being put through it does not create enough of an electromagnetic field to transmit power. So when the wire is looped around next to itself it acts like one big wire and creates a larger field than that of a single wire.

Once the field has been increased from a few micrometers to a few inches in this manner you can start to receive power. Due to the spin created by the field any circuit (electricity has to have a place to flow) placed within it will "resonate" this spin and begin to carry electricity on its own almost as if by magic.**

But this only goes so far. This field, while stronger than before and able to generate electricity, does not have quite enough power to be able to run a device receiving power through a single wire. And so it must be passively amplified (through another coil) before it can be sent to the components you are trying to use.

Once amplified in this manner there is enough voltage flowing through the receiving coil to power the device or components it is attached to.

PS This is a relatively basic and general explanation of how this works. A more detailed description of it can be found almost anywhere.
Wireless Energy Transfer
Electromagnetic Induction
Make Presents: The Inductor (Watch the whole series of Make Presents videos they explain almost all of the basic electronics components)

*Use the Right Hand Grip rule to determine direction of spin. Hold your right hand up in a fist with your thumb up. Your thumb represents the flow of electricity down the wire. Your fingers represent the direction of spin around the wire.

** This is the principle behind an Electro-Magnetic Pulse (EMP) the pulse creates so much voltage within the target's circuitry that it overloads all of the components, and destroys any form of magnetic storage.
happybuilder4 years ago
what's the extra hardware for?
4 years ago
for converting the ac input current into dc allowing you to connect cellphones, ipods and other dc appliances to the coil (it has its limitations)
4 years ago
ok, so I don't need to build that because I'm building a wireless batterie free mouse and pad.
4 years ago
computer mice are dc!!!!!!
theawesomeninja5 years ago
won't the magnetic field screw the memory of an mp3 player or something?
5 years ago
(removed by author or community request)
5 years ago
So my c200 Sansa won't be affected by it?
5 years ago
Yours Sansa C200 will be safe seeing as it is a solid state memory device so you can use this tech. with out erasing your MP3.
5 years ago
awesome! I think I might make one of these then!
4 years ago
ipod touch 2g work? yes or no
4 years ago
4 years ago
are you sure cuz i think touches use a hard drive?
4 years ago
I can assure u it has flash memory
4 years ago
ok
4 years ago
THat being said i dont actually own one, but i'd like to.
4 years ago
lol...smooth

4 years ago
ok  thanks abunch
5 years ago
It takes a significantly strong magnetic field (such as a lab deguasser) to do any 'damage' to hard drive memory mediums.

I would be more worried about the RF noise this thing is emitting.

KeviBear4 years ago
Where the LED is this picture is, couldn't you just attach a female usb port instead and then be able to charge ipods? Or would you need to add a 5v regulator somewhere so you don't over charge it and kill the battery?
wolfkeeper5 years ago
The energy vampire thing is probably a bit overkill. I think all you need is a step up transformer and a single diode and capacitor. The bead might be all you need to make the transformer if you wind it right; and if the load is the LED, you probably don't even need the diode, just a resistor to limit current. If you do this though, you may need to up the frequency, the bead works best at high freq.