Determining if the person opening the door is either inside or outside

So i would like to get some inputs on how to determine if the person opening the door is either inside or outside. I need a way to reliably determine it, something that will work on both sliding doors and ordinary swing doors. The sensor must not be on the door , it can be on the door jams or on the floors as long as its not on the door itself, but it is however possible to place passive components on the door as long as it doesnt need power such as magnets. It is very easy to determine if the door is opened or not, determining which side opened it proves to be a challenge for me

Here are my ideas so far.

The most reliable i can think of is putting pressure pads on both outside and inside. but the problem with this is its very costly not only the pressure pads are pricey but i have to remove the floor tiles also.

The second idea i have is to use PIR sensors, but i kind of doubt its reliability. would there be a level up solution to PIR sensor or maybe something to complement it

How about a IR sensor (emitter/receiver combo) on both sides with a suitable mirroring surface on the opposite walls? You can also use the floor and ceiling.

Wont that just be a predeccesor to the PIR sensor? I think i would trust the PIR sensor more than to make and calibrate my own emitter/reciever combo

Put this over the door, if person is in = no light …
then use light detector.

The thing hanging from the bottom is a PIR sensor :stuck_out_tongue: dont even the lights haha.

Well, it depends on the complexity you want.
IR sensor < PIR sensor < camera system

And also on the visibility of the system.
You can hide a small IR LED and a small IR photodiode/transistor in the tiny space between the floor tiles, run thin enameled wires out to a nearby wall, then cover the whole thing with transparent paint/glue for protection. Couple that with a small mirror on the ceiling directly above and you’re set.

Put a radar detector moule on. The inside pointing down.

taking inspiration from what you said i think i might have come up with something. I will place an IR laser just a few mm above the door knob and a maybe a tiny mirror reflecting back to the reciever on the door jam. On one side of the door touching a door knob would break that laser indicating that a person is on that side, using maybe a hall effect sensor we can also know that the door is opened. from there we can basically figure out the rest with logic.

laser broken & doork opened = person on side A
laser not broken & door opened = person on side B

It has to be a laser type IR emmiteer though

Im not familiar of radar modules can you recommend one?

Seconded. In particular, a directional one. The ones I’ve messed with are 360 degree detection and can see through wood, solid walls, etc. So they wouldn’t really be suitable for this application.

Consider mounting them in a sardine can!

A little modification on my previous idea - if you have lights on at least one side of the door, you can hide an always-on IR LED inside, pointed at a photodiode on the floor. You won’t need a mirror this way.
You can use a laser as well.

But, i think you should avoid lasers, especially invisible ones like IR. You don’t want to accidentally blind someone (or their pet).

oh wait you can get blind by invisible IR? even a 1mW laser? Planning to use those mini IR lasers and will even reduce its power more to about twice the minimum power for the reciever to see

Yes, maybe not totally blind, but the danger is real. The invisible ones are even more dangerous, because your eyes won’t naturally adjust to protect themselves.
I am sure everyone, who played with laser pointers have shined them at least once directly at their eyes. We may not be blind (yet), but better be safe than sorry.
Also, if someone with a pet stops in front of that door, there is a high probability that the pet would look upwards at their owner. They won’t even be able to tell if something bad happened.

A little reading material - Laser safety

An LDR will report a sudden change in the total amount of light falling on it. Very small, simple to use, and unobstrusive.

about radar

and yes, they can ‘see’ through walls. hence the ‘look down’ comment.

since sensors do no evaluate data, the user has to use logic to determine what happens.

you see a car pass, and see, a red Toyota, with it’s lights on, is passing from my left to my right.

an IR beam break see : break.

two sensors, one outside, one inside, may have one react first. first to react shows what side. the movement is.

however, if you knock on the door and stand there. and someone on the other side opens the door. how will you know ? and does that matter in this project ?

my first thought on the project was a PIR, so reliable that every alarm company uses more of them to detect people movement than any other sensor. door and window sensors don’t detect people, they detect a state or condition of an object.

a capacitance sensor, like used in car alarms could be put on the door frame/wall and detect a hand moving to the door knob.

A person on one side can insert a wire and open the door on the other side.
lots of ways to add confusion and complexity to the basic premise. :slight_smile:

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