AVR-Chat

Hi Jim,
That sounds like a great idea. Doing it on a PCB would mean that each 
antenna will be identical (and saves all that winding :-)).
The problem (for me) though is how do I work out how many turns I need (how 
wide the tracks need to be, etc.)
If you have any links I could checkout I'd appreciate it.
Cheers,
Ivan

----- Original Message ----- 
From: "Jim Wagner" <jim_d_wagner@applelinks.net>
To: <AVR-Chat@yahoogroups.com>
Sent: Friday, September 23, 2005 9:27 AM
Subject: Re: [AVR-Chat] OT: Where to get Custom Coils would


> Make yourself an antenna with a spiral trace on a circuit
> board! Resonate it with a capacitor to 125KHz and you
> should be in. The more sprirals, you have, the better,
> because the resonating cap will be smaller and the coupling
> to the tag will be better. At 125KHz, the coupling is
> primarily magnetic (like a transformer) rather than
> electomagnetic (like a radio). More primary turns should
> give you better coupling.
>
> Jim
>
>
> On Fri, 23 Sep 2005 09:22:53 +1000
> "Ivan Vernot" <ivernot@optushome.com.au> wrote:
>> Thanks Zack,
>> After seeing your post I checked Digi-Key.
>> As far as I can see, they only carry the 'TIRIS' (Texas
>> Instruments RFID)
>> stuff.
>> It is at 132KHz and uses quite large (~1m) antennae.
>>
>> I am after an antenna <100mm long  (65mm round would be
>> perfect) for use in
>> a 125KHz proximity card reader (think of an access
>> control application)
>>
>> BTW: I am in Sydney Australia.
>>
>> Thanks for the reply.
>> Cheers,
>> Ivan
>>
>>
>> ----- Original Message ----- 
>> From: "Zack Widup" <w9sz@prairienet.org>
>> To: <AVR-Chat@yahoogroups.com>
>> Sent: Wednesday, September 21, 2005 10:25 PM
>> Subject: Re: [AVR-Chat] OT: Where to get Custom Coils
>> would
>>
>>
>> >
>> > Hi Ivan,
>> >
>> > You didn't say where you are located.  Can you order
>> from Digi-Key?  They
>> > have a whole assortment of RFID antennas and coils in
>> their catalog.
>> >
>> > Zack
>> >
>> > On Wed, 21 Sep 2005, Ivan Vernot wrote:
>> >
>> >> Hello All,
>> >> Apologies for off topic post but I'm using an AVR for
>> this gadget ;-)
>> >>
>> >> I  am looking for a supplier that is able to wind an
>> open core coil to be
>> >> used in an RFID application.
>> >> The coil is used for the antenna of the RFID system
>> and is typically a
>> >> few tens of turns in reasonable heavy gauge wire
>> (30AWG or so) so that is
>> >> it relatively self supporting.
>> >>
>> >> Does anyone know of a supplier that can supply such
>> coils in <1K qty?
>> >>
>> >> Kind Regards
>> >>
>> >> Ivan Vernot
>> >>
>> >
>> >
>> >
>> >
>> >
>> > Yahoo! Groups Links
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>>
>>
>>
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