26-06-2012, 01:41 PM
Wireless-Power Transmission-Over-Short-Distances
Wireless-Power-Transmission-Over-Short-Distances-U.pdf (Size: 287.99 KB / Downloads: 74)
introduction:
Wireless Power
The power cord, I know you hate it. Sometimes, you just want to cut it apart! Well say goodbye to your power cords, because with the power of inductive coupling your
device will not need to be connected metal to metal. Seemlessly your device can be charged!
This instructable will show you the basics of creating your own cheap and easy wireless power mat, which you can use to power your device through the air!
I am now working on making an iPod Charger with this technology.`
My next Instructable in the making, is on transmitting data over inductive coupling
so please subscribe!
What is it? How does it work?
A few years ago MIT created a system for transferring power wirelessly. They transmitted power over a two-meter distance, from the coil on the left to the coil on the right,
where it powers a 60W light bulb. Back in 2006, this was a pretty cool thing. You can only imagine what the implications of something like this would be. Well, unlike most
of us, we do not have the time or material goods like MIT has. So i have made this simple and easy to follow Instructable, so all of you good people can experience the
joy of wireless power.
Inductive Coupling uses magnetic fields to transfer power. There is a primary coil, which generates a magnetic field. Then there is another secondary coil which is
composed of a capacitor and a coil, the capacitor creates a resonant circuit with the primary and secondary coils. Seem easy? Well, before publishing this instructable I
found many useful and a lot of non-useful info on the subject.
In my research I found, that to transfer power in very complicated. Once i did it I found that you do not need to go to MIT do do this sort of stuff. With a little
electrical know how, this is easy.
It all starts with the transmitter. This transmitter needs to create 147.7 kHz square wave AC signal. Let me take a minute to explain this all. Level one on the frequency
scale is Hertzs, then there is kHz, then MHz. MIT used a 10 mHz wave to drive there coils, but for this we will be using a 147.7 kHz signal so it does not get too
complicated.
The secondary coil has a 0.02 uF capacitor. This will allow the two circuits to be coupled therefore, transferring power efficiently. The 0.02 uF capacitor is used only for
this frequency, and the value of this capcitor will change depending on the frequency.
The primary coil creates a magnetic field, when another coil is placed near it, energy will be induced into it.
Creating the Primary Coil
The primary coil uses magnet wire, which is easy to get at .
Magnet wire has a very thin coating on the top of it. To get this off you can light a match and put the magnet wire in the flame for a few seconds. Take the two ends of you
coil and put it into the function generator on the top two screw terminals, one in each terminal. Polarity is not a problem right now because the signal will be AC. Now
place your 0.02 uF film capacitor in parrelel with the terminals you put the wire magnet ends into. Turn the function generator on and use your multimetter to get it to
somewhere near 147-149 kHz by turning the potentiometers. Make sure the switch on the left of the board is set to square, and your good to go. The top to terminals will
allow for an AC signal.
The Secondary Coil
This circuit is one of the simplest you can ever create. It is composed of magnet wire coil but smaller like the primary, a 0.02uF
capacitor also like the primary, and some leads you can attach things to. For LED's the circuit looks like that. Yet, for powering your iPod and other devices that use DC
power you need a diode bridge, or rectifier which can turn AC into DC to power your portable device. Take a look for yourself that the secondary coil has an AC output
which will only power LED's.