Embedding RFID tag in rubber donut

Guest
Any ideas on how to achieve durability with this kind of packaging?
After performing adequately for about 6 months, 6 out of 8 prototypes
have failed.

I'm guessing that the antenna wire must have broken off due to the
donut's (relative) flexibility, but have no way of verifying this on
account of having no clue how to separate the rubber from the embedded
electronics. In any case, the whole circuit consists of one chip, one
capacitor and the antenna which must be the weak point due to the
small wire gauge (36 I believe).

The donut-shaped package - and hence the tag's antenna - measures
approximately 4 inches in diameter.

Thank you.
--
 
<atavas@vdn.ca> wrote in message
news:c15a0eb2.0405251915.447969e7@posting.google.com...
Any ideas on how to achieve durability with this kind of packaging?
After performing adequately for about 6 months, 6 out of 8 prototypes
have failed.

I'm guessing that the antenna wire must have broken off due to the
donut's (relative) flexibility, but have no way of verifying this on
account of having no clue how to separate the rubber from the embedded
electronics. In any case, the whole circuit consists of one chip, one
capacitor and the antenna which must be the weak point due to the
small wire gauge (36 I believe).
Click to expand...
Almost certainly the transition between board and antenna.
36 ga is extremely small. Why not use copper braid, like solder-wick, and
put some heat shrink near the soldered part?
 
Subject: Re: Embedding RFID tag in rubber donut
From: "Dave VanHorn" dvanhorn@cedar.net
Date: 5/25/2004 8:23 PM Pacific Daylight Time
Message-id: <csWdnQQZZ4IJkCndRVn-hg@comcast.com

Now.. What are you doing? Tracking cops? :)
Click to expand...
LOL, brilliant comment!
Can you X ray the donut to find out if a wire broke?

Rocky

Rocky
 
Can you X ray the donut to find out if a wire broke?
Click to expand...
Very likely, 30 ga is pretty thin. The stress is all going to end up pulling
on the wire at the root.
 
On 25 May 2004 20:15:28 -0700, atavas@vdn.ca wrote:


I'm guessing that the antenna wire must have broken off due to the
donut's (relative) flexibility, but have no way of verifying this .......................

The donut-shaped package - and hence the tag's antenna - measures
approximately 4 inches in diameter.
Click to expand...
From the literature I have come across a RFID chip is small enough to
be injected under the skin. In fact this had been used as a sales
gimmick by a French or Belgian private club to ID their elite patrons
- automatic clearance to enter the club without regular ID checks,
access to restricted privileges, etc. Elsewhere it was used to keep
track of a small group of patients with mental disorders. This of
course raises heckles from civil liberty advocates about the porspect
of Big Brother abuses. Think 9/11 security measures.

Anyway the point I am trying to make is why does the poster's RFID
donut experiment have an antenna (and therefore implies it is attached
to a PCB big enough to solder it to)? This seems to be reinventing
the (wood cart) wheel.
 
Anyway the point I am trying to make is why does the poster's RFID
donut experiment have an antenna (and therefore implies it is attached
to a PCB big enough to solder it to)? This seems to be reinventing
the (wood cart) wheel.
Click to expand...
Sometimes it's difficult to get cops to hold still for the injections.. :)

There's probably a reason. I have some samples of what you're talking
about, large rice.
But, not ideal for every situation.
The OP might need more range on a reader than these offer.
 
"KLM" <klmok88@yahoo.com> wrote in message
news:lcc9b09d7u7ro894qbouqe67ceqp1c06hr@4ax.com...

From the literature I have come across a RFID chip is small enough to
be injected under the skin. In fact this had been used as a sales
gimmick by a French or Belgian private club to ID their elite patrons
- automatic clearance to enter the club without regular ID checks,
access to restricted privileges, etc. Elsewhere it was used to keep
track of a small group of patients with mental disorders. This of
course raises heckles from civil liberty advocates about the porspect
of Big Brother abuses. Think 9/11 security measures.
Click to expand...
Think "mark of the beast".
 
atavas@vdn.ca wrote:
Any ideas on how to achieve durability with this kind of packaging?
After performing adequately for about 6 months, 6 out of 8 prototypes
have failed.

I'm guessing that the antenna wire must have broken off due to the
donut's (relative) flexibility, but have no way of verifying this on
account of having no clue how to separate the rubber from the embedded
electronics. In any case, the whole circuit consists of one chip, one
capacitor and the antenna which must be the weak point due to the
small wire gauge (36 I believe).

The donut-shaped package - and hence the tag's antenna - measures
approximately 4 inches in diameter.

Thank you.
--
Click to expand...
Put a loop in the wire at the joint to allow flexiblity. Embed the loop
in a drop of VERY flexible medium. Then mold the donut around that.
mike

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message news:<csWdnQQZZ4IJkCndRVn-hg@comcast.com>...
Now.. What are you doing? Tracking cops? :)
Click to expand...

<g>... good one! That's not it, but good guess!
--
 
....
Almost certainly the transition between board and antenna.
Click to expand...
Yes, I tend to agree.


36 ga is extremely small. Why not use copper braid, like solder-wick, and
put some heat shrink near the soldered part?
Click to expand...
Can't quite visualize what you mean. Could you please elaborate?
--
 
The key issue is range, considering that the reader surface area is
small (also circular with ~4in. diameter).
--

Anyway the point I am trying to make is why does the poster's RFID
donut experiment have an antenna (and therefore implies it is attached
to a PCB big enough to solder it to)? This seems to be reinventing
the (wood cart) wheel.
Click to expand...
 
Can you X ray the donut to find out if a wire broke?
Click to expand...
On 2nd thought, even if the wiring shows up on an x-ray, I don't think
the break would...
--
 
atavas@vdn.ca wrote:
...

Almost certainly the transition between board and antenna.

Yes, I tend to agree.

36 ga is extremely small. Why not use copper braid, like solder-wick, and
put some heat shrink near the soldered part?

Can't quite visualize what you mean. Could you please elaborate?
--
Click to expand...
Instead of using a single piece of wire for the antenna, use something that is
woven like soldering braid -- presumably it would be much more resilient to
continuous flexing. Since the weak point is typically the point of contact
between the device and the antenna, use something like shrink tubing at the
point of contact to provide some rigidity.

cut-away view:

-----
(@@@@)*###############
-----

Key -
(@@@@) = device
* = solder point
--- = shrink tubing
### = braid (antenna)
 
On Wed, 26 May 2004 15:24:59 -0700, mike <spamme0@juno.com> wrote:

atavas@vdn.ca wrote:
Any ideas on how to achieve durability with this kind of packaging?
After performing adequately for about 6 months, 6 out of 8 prototypes
have failed.

I'm guessing that the antenna wire must have broken off due to the
donut's (relative) flexibility, but have no way of verifying this on
account of having no clue how to separate the rubber from the embedded
electronics. In any case, the whole circuit consists of one chip, one
capacitor and the antenna which must be the weak point due to the
small wire gauge (36 I believe).

The donut-shaped package - and hence the tag's antenna - measures
approximately 4 inches in diameter.

Thank you.
--

Put a loop in the wire at the joint to allow flexiblity. Embed the loop
in a drop of VERY flexible medium. Then mold the donut around that.
mike
Click to expand...
Or make the whole pcb-antenna solution in a hard plastic case that is
embedded into the rubber
 
<atavas@vdn.ca> wrote in message
news:c15a0eb2.0405261813.652e6dc7@posting.google.com...
Can you X ray the donut to find out if a wire broke?

On 2nd thought, even if the wiring shows up on an x-ray, I don't think
the break would...
--
Click to expand...
You might be surprised - where I work they do "X-ray welding," which
is ordinary TIG welding, and they X-ray the joint to detect porosity,
cracks, any kind of irregularity. These are steels and nickel alloys,
and copper should show up just because it's denser than rubber.

But strain relief is the ticket.

Good Luck!
Rich
 
<atavas@vdn.ca> wrote in message
news:c15a0eb2.0405261801.81e2c37@posting.google.com...
...

Almost certainly the transition between board and antenna.

Yes, I tend to agree.


36 ga is extremely small. Why not use copper braid, like solder-wick,
and
put some heat shrink near the soldered part?

Can't quite visualize what you mean. Could you please elaborate?
Click to expand...
Solder-wick is a copper braid, very flexible, available in different widths.
Another thought occurred to me though, miniature coax, using the shield as
the antenna.
This comes with a plastic overcoat already. Just do the attachment inboard
on your PCB, so that you have a short length laying over the edge of the
PCB, and use a tie-wrap to secure that point for strain relief. Should last
a LONG time.
 
<atavas@vdn.ca> wrote in message
news:c15a0eb2.0405261808.46d5602f@posting.google.com...
Good thinking. Question though: would the copper wiring show up on the
x-ray?
--

Can you X ray the donut to find out if a wire broke?
Click to expand...
Yes, but the trick is getting access to X-ray equipment.
Some PCB houses have them for BGA work, but they aren't likely to take in
"look inside this thing" jobs.
 
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