Cat nose scanner

Expanding the scope of application of a biometric access control system to other creatures opens up truly amazing opportunities.

It so happened that on the territory of the manufactory where I am located there lives a fairly large family of blue-black cats, all brothers from the same mother, but from different litters. We simply call this entire pride Bandits, based on their corresponding character and behavior. Of all this flock, I liked one cat the most: the most adequate and intelligent; and it is he who I sometimes allow into my offices.

And I wanted to let that beautiful cat in and weed out the rest so that they wouldn’t misbehave in my absence. And the thought came into my head about a access system called KotSKUD – cat access control system.

❯ KotSKUD concept

I thought for a long time about how to make this solution simple, cheap, repeatable and not require a serious power supply. Once again, having scratched my beloved Bandit’s withers, I came to the conclusion that it is best to use a fingerprint scanner for these purposes.

Scratching my beloved Bandit

A cat's nose or paw has a unique pattern, just like the pattern of a human's fingerprint. So all that remains is to find a way to scan the paw pad or nose (depending on what the cat likes best).

I spent quite a long time analyzing what was available and inexpensive on the market, and then settled on an optical fingerprint scanner model FPM10A. There are a huge number of examples and software for it, there are a bunch of libraries in Python and Arduino, which means, in theory, there shouldn’t be any problems with it.

❯ A few words about the design of the optical fingerprint scanner

An optical fingerprint scanner works on the principle that light at a certain angle is completely reflected at the boundary of two media. And if some object touches this boundary, then this reflection is disrupted and the imprint of this object can be read. As an example, here is a diagram of the R307 optical sensor:

taken from this site

An optical sensor is a very complex device, which contains a prism that implements the boundary of media, and a full-fledged camera with a processor that allows you to read fingerprints. When there is no touch, a smooth white light enters the camera lens. And if the nose touches our CatSKUD, then the intensity of the light decreases, and the camera thus photographs the print.

Next there is a complex fingerprint recognition system based on a database, using some cunning algorithms, the operation of which is unknown to me.

❯ Connecting the FPM10A scanner

The beauty of the scanner

FPM10A

is that it is connected in the usual UART way and is powered by 3.3 volts. To connect it you will need any regular USB-UART adapter. I will not dwell in detail on the method of connecting this sensor, everything is described in sufficient detail

in an official document

I needed to make several passes with a soldering iron to connect it to the computer, but even a child could do it.

The scanner of my CatSKUD is connected and ready to work

It was just a matter of software. I was too lazy to tinker with Python libraries, so I decided to start with a demo program for these sensors, running it on a virtual machine. The program is very unstable, sometimes crashes, and does not always see the sensor. And I think this is due to the fact that it is very poorly implemented.

But in general, everything is like in the joke: my cat used to not like vacuum cleaners, but that’s okay, then he got used to it… So I got involved, and then I even started to like her.

Preparing software for testing

The most interesting part has come – to move on to full-scale testing.

❯ Full-scale tests

Probably the most difficult and exciting moment. The bandit was fed and treated as kindly as possible. I think he has never in his life experienced such warm attention to his person since the time of his birth, and certainly did not expect that he would receive so many goodies. In all experiments with the scanner he showed active participation and interest and even watched what would happen.

Paw print scanner

In general, it seemed to me that teaching a cat to poke its paw into the scanner would be the simplest action. Plus, this is a fairly simple and easy operation.

But I was faced with a harsh reality: Unlike pets, who have the softest pink pads, factory Bandits have paw soles more like hard sandpaper. And no matter how strange it may sound, the scanner flatly refused to scan any cat’s paw. Or if I did, the output was something completely unintelligible. That's why I won't show you the cat's paw print.

Cat nose print

I can’t say that Bandit was delighted that they wanted to scan his nose, but he didn’t put up much resistance either. In general, in this entire procedure, no violent or unpleasant actions were used against the beloved cat, everything was quite voluntary, and the cat was very intelligent. The problem was rather that he did not want to touch the scanner and freeze so that his nose would be scanned properly.

Scanning a cat's nose

Still, after several not very successful attempts, Bandit agreed to more calmly poke his nose into this luminous thing, and the prints were successful. After that, I began saving the results on the computer, and with incredible curiosity, he followed all my actions, which simply amazed me, as if he himself understood everything that I was doing there.

What are you doing there?

The moment of truth has come, is it possible to use an optical fingerprint scanner for cat noses and further implement my CatSKUD?

❯ results

You, just like me, are eager to see what we managed to scan there? There weren’t many successful scans, as I already said, Bandit was moving his muzzle quite quickly, and my conscience did not allow me to show violence or somehow record it.

Here are the first two more or less successful shots of a cat’s nose print, feel the uniqueness of the moment: you see them first.

The first prints of cat noses

In the end, I managed to get a more or less clear picture of a catfish. And just at this moment, Bandit got tired of this game, and he decided to leave.

A clear shot of a cat's nose

I consider this a real success!

❯ conclusions

The main conclusion from this whole undertaking is this: the imprint of a cat’s nose can be used in the KotSKUD system to give the animal access to the premises.

However, I did not take into account several factors:

Collection of an array of prints of one nose. It takes a long time to collect a sufficient number of nose prints from different angles for correct recognition and addition to the database. But the cat does not want to deal with these nonsense for so long and begins to resist.

Training. The second factor that for some reason didn’t occur to me is that the cat will need to be trained to poke its nose into this glowing thing. And, as practice has shown, the cat does not want to poke his nose, and even with sufficient force so that the print is clearly readable. And no amount of treats or stroking will tempt him into this action.