0
\$\begingroup\$

I have experimented with attaching my work RFID access card to the back of my iPhone 6 which is made from aluminium. However it appears that the phone is acting as a faraday cage and preventing my card from being read.

Is there a material I can place between the back of my phone and my access card to disable the faraday cage effect?

\$\endgroup\$
  • 1
    \$\begingroup\$ I see absolutely no evidence of a faraday cage, unless you are disassembling your telephone and placing the access device inside it. What sounds much more likely is that RF (intentional and stray) from the iPhone are swamping the receiver of the RFID reader, making it -- effectively -- deaf as a fence post. \$\endgroup\$ – Lawrence NK1G Jan 10 '17 at 2:00
  • \$\begingroup\$ You could be right. The reader does make a "rejected" sound, which indicates it is reading the card but the signal its receiving is not correct. If interference is the issue, is there any material I can place between the phone and the card to make the card readable? \$\endgroup\$ – Josh Gilfillan Jan 10 '17 at 2:10
  • 3
    \$\begingroup\$ Ten to twenty inches of air-gap should be sufficient. :P \$\endgroup\$ – Lawrence NK1G Jan 10 '17 at 2:17
  • \$\begingroup\$ "Anti-Metal" RFID material would go between the tag and your iPhone's back. Google it. \$\endgroup\$ – Passerby Jan 10 '17 at 2:38
  • \$\begingroup\$ Would something like this do the trick? \$\endgroup\$ – Josh Gilfillan Jan 10 '17 at 3:51
2
\$\begingroup\$

Try some rubberized ferrite sheet material - some are specifically designed to alleviate problems of this type (at 13.56 MHz). I seem to remember Ferroxcube making this product and I think Wurth do now: -

enter image description here

Wurth Elektronik WE-FSFS Flexible Sintered Ferrite Sheet WE-FSFS adhesive flexible sintered ferrite sheets for EMI suppression and magnetic shielding with a high permeability and low losses at communication frequency. These WE-FSFS flexible ferrite sheets improve the efficiency of Wireless Power Transfer (Qi-WPC, PMA, A4WP & WCT) and improve the performance of NFC and RFID communication systems.

This also might be a useful read (again by Wurth):Going Wireless with Magnetic Shielding

I've used it to alleviate the energy losses in transferring 600 kHz magnetic power to a coil fixed to a stainless steel object. Without the ferrite behind the coils the power loss was just too great and I suspect this is what happens when you attach your tag to the case of your iPhone.

\$\endgroup\$
0
\$\begingroup\$

a)Metal reflects magnetic fields, for certain frequencies and certain thicknesses and conductivities. The closure of metal lids on 1 nanoVolt RIAA preamps.......moves the 60Hz hum levels UP.

b)Metal also permits eddy currents, which tend to cancel the arriving magnetic flux.

However, A & B may be related.This question needs an EM jock. That ain't me.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.