[HN Gopher] Arduino FDX-B (animal ID chip) reader built from dis...
___________________________________________________________________
Arduino FDX-B (animal ID chip) reader built from discrete
components
Author : RicoElectrico
Score : 90 points
Date : 2024-05-30 17:03 UTC (3 days ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| 05 wrote:
| Personally I would use a timer capture channel for input, that
| way you get automatic timestamp capture and you don't depend on
| gpio isr handlers firing on time in case there's some other
| concurrent interrupt.
| RicoElectrico wrote:
| Oh, so it got to the frontpage via the second chance pool. Nice
| :)
|
| Anyway I wanted to build something like this as soon as I chipped
| my kitty half a year ago, but this popped up just recently!
| qingcharles wrote:
| My first thought was "can I hack the Android NFC reader to read
| my dog"? Sadly not, but I think if smartphones could read the
| chips it would be cool.
| stavros wrote:
| This is the sort of pointless hackery I love seeing. Keep it up!
| floating-io wrote:
| This was a fascinating read if for no other reason than seeing
| how the filters were assembled. I have much more understanding of
| digital than analog, to say nothing of RF stuff.
|
| I would love to see more stuff like this that is so
| understandable! Makes it seem much less like black magic...
| CamperBob2 wrote:
| Yes, it's a nifty technique. One detail that might not be
| immediately apparent is that it drives the LC circuit in a
| series-resonant configuration, where it looks like a low-
| impedance load that can accept a lot of current from the
| transistor half-bridge, but it receives the response in a
| parallel-resonant configuration, which is good for sensitivity
| when driving high-impedance loads like the 22K input resistance
| presented by the opamp circuit.
|
| For this topology, best results will depend on low-impedance AC
| bypassing on the Vcc line, which he doesn't show on the
| schematic. I'm sure the Arduino's supply input has enough
| capacitance to take care of that, but if you adapt the circuit
| to other uses it's something to keep in mind.
| spdustin wrote:
| Excellent use of simple discrete filters rather than trying to
| post-process in code.
| sorenjan wrote:
| This is really cool and I like how the author describes how it
| works step by step. It makes it interesting even if you're not
| going to build one yourself.
|
| I'm guessing that the data you extract from the RFID chip is some
| ID number that you need access to a database to do anything with?
| And that database is closed and only available for vets and
| similar? Either way, checking for the existence of a chip can
| probably be valuable enough sometimes.
|
| And it can be integrated with a smart cat door or other local
| projects where you want to identify your pet.
| duskwuff wrote:
| > I'm guessing that the data you extract from the RFID chip is
| some ID number that you need access to a database to do
| anything with? And that database is closed and only available
| for vets and similar?
|
| Mostly correct:
|
| Many pet ID microchips also have a temperature sensor for some
| reason, which can be read out along with the fixed chip ID. But
| you're correct that the chip itself doesn't hold any owner
| information.
|
| There are dozens of different microchip ID databases; some of
| them are linked to specific chip manufacturers, others are
| general-use. Generally speaking, the registries don't give out
| owner contact information; instead, they'll contact the owner
| themselves when notified that a lost animal has been found.
|
| The AAHA has a tool that'll query most of the major databases
| at:
|
| https://www.aaha.org/for-veterinary-professionals/microchip-...
| anthomtb wrote:
| Awesome project with a great README. This makes me want to dust
| off my ancient analog electronics knowledge.
|
| Does anyone know why the second stage op-amp cleaned up the
| signal so much? It appears to have removed a higher-frequency
| oscillation, leaving a very clean, nearly square-shaped wave.
| duskwuff wrote:
| The second op-amp is configured as a comparator. It drives its
| output to the positive rail when the input exceeds a threshold,
| and low otherwise. The higher-frequency oscillations aren't
| anywhere near the threshold, so they disappear.
___________________________________________________________________
(page generated 2024-06-02 23:01 UTC)