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Participant

Join Date: Mar 2017
Posts: 1

Magnetic Resonance Power Source and Receiver

03/03/2017 8:20 PM

So I've decided to work with wireless energy for my senior project. My goal is to have one transmitter power two devices through single coil, loosely coupled magnetic resonance. I'll likely start with basically powering two separate receiver circuits with LEDs. My question is, How do you construct acquitted coils that hold their form at exact intended dimensions (i.e. height: 10 cm, diameter: 5 cm, loop spacing: 1 mm, etc.)?

I'd also like to figure out the output at varying distances between two or more coils. Would there happen to be a formula to figure this out? or all trial and error?

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#1

Re: Magnetic Resonance power source and receiver

03/03/2017 8:30 PM
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#2

Re: Magnetic Resonance power source and receiver

03/03/2017 10:35 PM

EngineerTechStudent, Microchip Corp has published a real nice application note on RFID technology, which uses much the same principles as your project, and their app note answers many if not all of the questions you asked. About 50 pages: http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf

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#3

Re: Magnetic Resonance power source and receiver

03/05/2017 12:02 AM

Welcome to CR4. I'm not sure what you mean by acquitted coils. I've wound a lot of coils in my lifetime, and only used formulas for inductance and resonance. I've used wooden dowels and PVC or ABS pipe, and wrapped the wire as close as possible. Use Scotch tape to hold it there while resting. I drill a small hole at each end to put the wire through to keep it from coming off. Polyurethane can be used to hold the wire in place too. Distance between coils may be trial and error (I don't know a formula). You could use pipes of 2 diameters such that one fits inside the other. Then you can move them for proper coupling. Hope this helps.

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#4

Re: Magnetic Resonance Power Source and Receiver

03/05/2017 1:19 PM

For starters, Google is your best friend. I've done a project based on loosely coupled wireless charging and there was a lot of trial and error work, taking measurements as variables were changed (one at a time to avoid confusion). Please note that the coupling coefficient (k) can change from more than 0.9 (near perfect) down to zero, and even go negative based on coil orientation. Working with LTspice to simulate variations will help with understanding of the trade-offs for losses and efficiency. The Yahoo LTspice user's group has some examples at "Files>Tut>Transformers>Transformer equivalent AC and Tran circuits_03.asc" , You may need to join the group to access the files.

Your design must consider variations from your request for any "exact intended dimensions", since real-life doesn't understand anybody's intentions. Your experiments should give you a lot of items to consider. Pick up a development kit for Qi (pronounced Chee), like the kit at https://www.adafruit.com/product/2162

Have fun,

Carl

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