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NFC field generator

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grymoire:
I am working on an art project, and I want to build a thin panel that can generate an NFC field which can power some NFC LEDs, such as  https://www.sparkfun.com/products/14888.

All I need is to light them up. I would appreciate any help. A thin design would be great, but I also am interested in increasing the XMIT range, so I can light them up from a distance. I don't think I need to read any information.

Thanks

Berni:
You basically just need to power a coil of wire with the right frequency AC signal. NFC tends to use around 13MHz so those LED tags are probably optimized for that.

How you generate the alternating current for the coil is completely up to you. But i suspect that getting it to work over a long range would include large coils and a lot of power put into it.

grymoire:
Yes, NFC is 13.56Mhz. I found some NFC coils that are used for smartphones. And I can get an NFC board with a build in antenna. I don't want to use a large board if I can avoid it. It's the
--- Quote ---How you generate the alternating current for the coil is completely up to you
--- End quote ---
part is where I need the help.

Berni:
Well you need to make an oscillator that generates the desired freqency, Any oscillator can be used or even a microcontroler can be used to toggle a pin at that rate. Whatever you are most comfortable using.

That needs to be put trough some sort of power stage. This means using a transistor to switch the power to the coil at that freqency or using some sort of driver chip to do it.

You also might want to have a capacitor wired across your coil and tune it to a value that makes the capacitor and coil oscillate as a LC circuit at the desired frequency. Take it step by step and play with it until you get it working.

judge:
I'm just trying to do the same thing. I found a circuit for an oscillator here that uses three NAND gates and a 13.56MHz crystal (and a few discretes). The oscillator basically works but the voltage is kind of low (around 2V p2p), plus the waveform looks very noisy. I'm not sure if the noise is real or an artifact of me hooking up my ancient oscilloscope.

I figured I could maybe feed the signal into the gate of a MOSFET to switch the full 5V, but the MOSFETs I have to hand are too slow (rise time of around 200ns!). So I was wondering if anyone could point me at a suitable part, advise about how to clean up the waveform, tell me that this will never work and I should do something else instead?

Also curious if the OP every got this to work?

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