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PCB Induction Charger

J22L

Jan 24, 2013
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Hi, I am new to this forum and I need some help.

I am working on a science fair project and I am making a PCB induction charger. I have etched my coils onto my copper-clad board and started some testing using a 22V input. No power transfer occurred between the two boards. I tried adding a 470ohm resistor to create a load but that did not work. I do not know what I need to do to be able to transfer the energy. Attached is a picture of my setup.
 

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Raven Luni

Oct 15, 2011
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You must use an AC source, not DC. Induction is a property of electric / magnetic flux (ie the field must be in a constant state of change). With DC your coil is just a resistor / weak magnet and basically does nothing useful.
 

J22L

Jan 24, 2013
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Oh, well I originally had it hooked up to a 9V battery so that explains why that didn't work, since it is DC. And I then hooked it up to that thing (I have no idea what it is called ) that has the bread board on it. I'm not sure if it is AC or DC though. I believe it is AC, but not sure. If it is DC and not AC, what could I use as an alternative to test my project using AC? Thanks.
 

Raven Luni

Oct 15, 2011
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You need a high frequency oscillator capable of delivering a moderate - large current at the desired voltage (high frequency = greater efficiency). You will then need to rectify the induced current at the other end.

Basically the 2 coils combine to make a transformer - so transformers should be the starting point for your research (and it looks like you will need to do a fair bit of it).
 

davenn

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Measure it with your meter and see if its AC or DC :)

you may need to buy a mains 115VAC (240VAC - depending on your countrys mains voltage) input to say 16V AC output then try that

Dave
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Dave, Take a close look at the etched "coil". It will have very low inductance.

J22L you need a spiral with one connection in the centre and one at the edge. Your design has as many "un" turns as turns, leaving a net number of turns close to zero.

Once you re-etch the board (perhaps you could also get away with moving one connection to the centre) then you'll need to use a relatively high frequency oscillator (perhaps several hundred kHz).

If you have equipment that can measure inductances (most multimeters that do so do not measure low enough inductances) then you can make some real calculations.
 

davenn

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Dave, Take a close look at the etched "coil". It will have very low inductance.

J22L you need a spiral with one connection in the centre and one at the edge. Your design has as many "un" turns as turns, leaving a net number of turns close to zero.

Once you re-etch the board (perhaps you could also get away with moving one connection to the centre) then you'll need to use a relatively high frequency oscillator (perhaps several hundred kHz).

If you have equipment that can measure inductances (most multimeters that do so do not measure low enough inductances) then you can make some real calculations.

yeah just doesnt look good huh, definately needs a spiral one feedpoint in the centre and one at the outer edge.
You cant have the ingoing spiral beside the outgoing spiral. I would expect one would cancel the other out.

Dave
 

J22L

Jan 24, 2013
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Here is a look of my boards up close. I was going to try to power it with a 9V battery, but then I found out that wouldn't work.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Here is a look of my boards up close. I was going to try to power it with a 9V battery, but then I found out that wouldn't work.

Yep, and we've already answered your question, told you why, and suggested what you need to do to make it work.

Anything else?
 

J22L

Jan 24, 2013
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I think I have gotten the help I needed. Thank you all.
 

J22L

Jan 24, 2013
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Hi, I am working on a new design for my coils. I am not sure if it will work though. The coils are approximately 0.15in wide..
 

J22L

Jan 24, 2013
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Forgot to add the picture.

Thanks for all the help.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Well, those will certainly act as inductors. However I think you'll need a high frequency to be able to use them effectively.
 

J22L

Jan 24, 2013
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Do you have a coil design(s) that you would suggest? I am running out of time to work on my science fair project..

Thanks again.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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lots and lots and lots more turns. If you;re using double sided board you can have part of the coil on each side. Just make sure that the current always goes in the same direction. (looking at the board it will appear to be clockwise from one side, and anti clockwise from the other).

Have you got some sort of signal generator that operates at a high frequency?
 

J22L

Jan 24, 2013
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Somebody told me that the coil starts have to be on opposing sides, that they could not be next to each other? How many turns do you recommend I would need?
 

J22L

Jan 24, 2013
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I have a Wavetek Model 30 Function Generator (http://www.radiomuseum.org/r/wavetek_function_generator_30.html) to use for my alternating current. Do you think this produces enough to test my design? I have tested my original coil designs and I am getting nothing. I am working on a new design to test over the weekend. I am wondering if my original design would work as long as I put the coil starting on the outside and ending on the inside and then solder my leads to each. I have included a picture to explain. None of the measurements are exact and my actual design will include many more turns, but I just made the picture quickly to explain what I mean.

Thanks for all the help.
 

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J22L

Jan 24, 2013
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This is my original design for my first set of boards.
 

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davenn

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This is my original design for my first set of boards.

yup thats the one we told you it wouldnt work as it is

now if you had that many turns (spirals) starting at the outside and finishing in the middle, you would
be starting to get close seeing some signal transfer over a cm or so

Dave
 
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