Motion / proximity sensors - fancy experimenting for me?

[Mrs Pingu]

We currently have one of these https://www.amazon.co.uk/Byron-Wireless-Touch-Free-Sensor/dp/B09644BG81?th=1 as a kitty door bell - it acts as a proximity sensor.
It worked mostly ok last year but this winter we're having problems with it ringing constantly, even when it's installed in a sealed food container to keep the rain off it, I suspect the battery doesn't like the cold or the humidity or something.

I did think about replacing the bottom panel of the door with a glazed unit and putting the door push/sensor inside but the current doorbell sensor doesn't work through the DG unit. (No to cat flaps because $reasons)

So does anyone else have something with a sensor that they fancy experimenting with for me? (Save me buying something and then finding it doesn't work) Like a Ring doorbell, or a Shelly Blu Motion sensor, or similar to see if it will work through glass?

[Kim]

PIR isn't going to work through glass, I don't think.  A microwave sensor should.  Or something machine-vision based (in as much as machine-vision things ever work).

AIUI you have to get up close and personal to read the RFID chip inside a cat, so that's a non-starter without a cat flap type opening to constrain it.

A reflective optical sensor might work, subject to the albedo of the cat and there not being too much sunlight.  I've been mucking about with a cheap reflective beam sensor (of the type designed for controlling motorised gates and similar) for detecting BHPCers with dodgy tags^[1] riding through the finish line, and while it's intended to detect the beam being broken when it's bounced off a retroreflector up to about 10 metres away, it also does a reasonable job of detecting the reflection from random objects^[2] in the under-half-a-metre range.  You can get small industrial sensors designed specifically for this sort of short-range sensing: think hand-drier.

Obviously a beam-break could also work, but would require Stuff be mounted outside.  See also pressure sensors, capacitive touch and so on.



_{[1] If you could attach an Impinj UHF tag to the cat and mount a circular-polarised antenna above the doorway that would work really well, albeit a couple of orders of magnitude over budget.
[2] Chairman Al's legs, chequered flags, that sort of thing...}

[Diver300]

A beam-break sensor with a retro-reflective reflector would work, with only the reflector being outside the house, and no wires needed to it.

https://www.ebay.co.uk/itm/275278767611

[Kim]

A beam-break sensor with a retro-reflective reflector would work, with only the reflector being outside the house, and no wires needed to it.

If you can keep the sunlight off it^[1] and ensure the cat's going to walk through the beam that might be a good approach, as you know exactly where/what it's detecting.


_{[1] My BHPC experiments began with a sensor like that mounted for convenience inside the CCTV enclosure alongside the camera it was triggering.  Worked really well when we tested it in the garden over the winter, but only worked intermittently at races over the spring/summer due to the brighter sunlight.  It's now mounted at the end of half a metre of drainpipe, which seems more promising, at least in September levels of insolation.}

[Regulator]

Get yourself a cantankerous Jack Russell.  Guaranteed to let you know when any animal (be it a cat, squirrel or another dog) or human is within 50 feet of the house.   

[Mrs Pingu]

Well, that got technical quickly!

Unless I misunderstand I don't think the beam break sensor thing will fly as it's a south facing door? (And I dunno where the reflector would go either). Microwave I also thought of - and presumably I could put behind a non glass door panel?
I was trying to find out what sort of sensor the Shelly was last night but failed.

[Kim]

I was trying to find out what sort of sensor the Shelly was last night but failed.

Looks like a PIR, based on the specifications and this image:

[lissotriton]

Most battery powered cameras/video doorbells use a PIR sensor.
But a wired camera could use pixel based motion detection. So that could work through a window. And some have animal/pet detection.

[HTFB]

Mount a freestanding cat flap outside, wire it to a bell, and train the cat to climb through it?

[Feanor]

Pressure pad wot it would stand on?

[Kim]

But a wired camera could use pixel based motion detection. So that could work through a window. And some have animal/pet detection.

Might be practical if you can arrange the camera so that there won't be any incidental background motion in the area occupied by the waiting cat.

Incidentally, I played with using OpenCV to detect HPVers crossing the finish line, and had promising results from the KISS approach of detecting the presence or absence of a QR code target (ie. the three corner squares) in the field of view, thereby not having to worry about movement from spectators and foliage and so on.  The jam-filled babbage engine could process about 10 frames per second this way, which I reckoned was just about adequate for the speeds involved.  The sticking point was that it would have required a QR code on the opposite side of the finish line that was approximately a metre wide and wouldn't flap about in the breeze.  OTOH, detecting a cat sitting on a known doormat would seem a lot less computationally challenging.

I can't help thinking that, regardless of the sensing technology employed, it will be defeated by the contrary nature of cats...

[Mrs Pingu]

The current doorbell thingy does actually work quite well, when it works...

[Kim]

Wonder if that's because it's sensor is false-positiving, or because of the usual wireless things being inherently rubbish due to their reliance on a) radio and b) flatteries.

Hm.  I'm now thinking of the touch-free door release button my GP surgery uses.  This sort of thing https://www.acornfiresecurity.com/flush-mount-touch-free-infrared-exit-button-stp-nt200

[Mrs Pingu]

Hmm, not sure, but the little light in the sensor window flashes constantly when it's stuck in ringing itself to death mode.

That is interesting Kim, wonder if I could make (or GAMI) that work.

I've had a look at pressure pads but most of the ones I've found want 25lbs over 50mm2 which is a bit much for kitties.
I did find this but it looks a bit beyond my skills. https://www.tekscan.com/blog/flexiforce/how-create-pressure-sensor-pad does seem to have adjustable force sense option tho.

[Feanor]

I've had a look at pressure pads but most of the ones I've found want 25lbs over 50mm2 which is a bit much for kitties.

And yet the one in the passenger seat of our Ford Focus triggers teh seat-belt bings if I place so much as an empty crisp bag on it!

[Mrs Pingu]

True, dat.

[ian]

Indeed, our camera in the porch doesn't work through the glass door, so is triggered by the motion sensor on the camera that overseas the driveway. Yes, I do live in a high-security prison. For bears. More Pawshank than Shawshank.

This gives me views of couriers reading and ignoring the note to put parcels in the box behind the porch* and then fleeing down the driveway before I catch them.

*according to the one I did catch, he was apparently under orders from above to only leave and photograph it on the actual doorsteps. Some do seem able to comprehend the instructions and photograph it in the box.

[SteveC]

I know you said 'no to cat-flaps', but ours, which reads the microchips, can be easily locked for either incoming or outgoing.
We are currently setting it to 'no escape' if we're away overnight as something spooked Sam last week and we're still a little anxious about him.

[Mrs Pingu]

I know you said 'no to cat-flaps', but ours, which reads the microchips, can be easily locked for either incoming or outgoing.
We are currently setting it to 'no escape' if we're away overnight as something spooked Sam last week and we're still a little anxious about him.

It's not primarily about our house, it's that once trained to use a cat flap Pumpkin will be able to get in other people's houses. Food obsessed Pumpkin + random cat food + delicate digestive system = poopocalypse.

[SteveC]

I see! And understand.