NFC signal amplification

Discussion in 'Digital Circuit Design' started by dudeism, Jul 13, 2016.

  1. dudeism

    Thread Starter New Member

    Jul 13, 2016
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    Hey, I am making an NFC based project and want to power another circuit around 10-12 V using nfc from my phone. Is it possible? Which opamps should I use?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    If you mean generate power from the NFC signal, I believe the answer is no.
    NFC is used to transfer signals, not power.
     
  3. dudeism

    Thread Starter New Member

    Jul 13, 2016
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    If I attach an LED to a copper coil antenna it glows with some voltage. Can this power another circuit?
     
  4. DickCappels

    Moderator

    Aug 21, 2008
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    Possibly but very little power would be available. Is there any reason you can't try some experiments, such as by adding a capacitor to your coil to make it resonant at 13.6 MHz and then use a detector (such a Schottky 1N60 or a Calmos CMS 8250 LF zero bias detector followed by a low pass filter and then see what kind of power you can get out of it? Increasing the number of turns should increase the voltage but remember to change the capacitor to keep the resonant frequency at 13.56 MHz.

    You can take power (but not much!) from across the capacitor in the circuit below.
    upload_2016-7-14_12-54-45.png
     
  5. dudeism

    Thread Starter New Member

    Jul 13, 2016
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    How can I measure the exact current from LEDs ? Its AC current and fluctuating. Can a multimeter do it?
     
  6. DickCappels

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    Aug 21, 2008
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    Individual LEDs do not conduct AC, at least they don't last very long in that mode. Your LED is probably acting like the diode in the circuit.

    You might be able to make an estimate of the current by comparing the intensity of the glow from the LED with that of the glow when running from a direct current source such as a battery, a pot and a fixed resistor in series.

    If you make the diode detector you can measure millivolts and milliamps and calculate power.
     
  7. dudeism

    Thread Starter New Member

    Jul 13, 2016
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    Can I use an OPAMP (mcp6282-e/sn) to amplify the signal? I found this circuit online. Will this help? Capture.JPG
     
  8. DickCappels

    Moderator

    Aug 21, 2008
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    Not with that opamp -it runs out of gain at 10 MHz.

    Your original intent was to derive power from the NFC signal from your phone. If you use and amplifier, from where would the amplifier get its power? Or, has your goal changed?

    Maybe you would be interested in a RFID or wireless charging project, both of which can provide more power.
     
  9. DickCappels

    Moderator

    Aug 21, 2008
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