A device that turns the room light on and off when you enter/exit the room

I've looked through the posts on this topic but haven't found one - I'm concerned with a device that will turn the light on in a room when you enter it and turn the light off when you leave.

1. a normal lighting motion sensor - unless necessarily there must be no time delay after exit
2. the cheapest photo line connected to a bistable relay - but what if two people enter and only one of them leaves? The other stays in the room with the lights off.
3 - How about reed switches? Then the door must remain open.
4. all of the above connected at the same time - full blast 🤭

There are several solutions to this problem. The simplest is a limit switch mounted in the door. Unfortunately, inaccurate closing or opening can cause the system to malfunction. "Ordinary" motion sensors are not very precise and it can happen that the light goes out when there is not much movement.

However, a special presence sensor , equipped with much more accurate detection systems (often several), will work much more precisely, also detecting micro-movements of the object. An example of this type of device could be the STEINEL IR Quattro HD or the KANLUX SENTO, but also many others. Of course, the detector (or detectors) must be selected according to the dimensions and shape of the room, also taking into account the optimum place for their installation.

Mobali wrote:

STEINEL IR Quattro HD

These sensors are some kind of cosmos.
Can detect finger movement when typing on the computer keyboard.

adwlodar wrote:

These sensors are some kind of cosmos. They can detect finger movement when typing on a computer keyboard.

Maybe not "cosmos", but they work very well in this role. The disadvantage of any 'ordinary' PIR sensor is precisely the low sensitivity and the light switching off despite the presence of a person in the room.

Erbit wrote:

You can build a people counter in a room....

It is certainly possible and would certainly work very well. However, I think it is a more complicated solution.

Unfortunately, none of the solutions proposed by colleagues fit my particular situation, namely, the room is entered from the corridor through an opening not equipped with a door, so reed switches are out. This is a room equipped with bookcases, behind which the person there may be "invisible" to the sensor's eye.
I thought that there were ready-made solutions in which - on entry - the actuator is put into a "high state" (lighting up) and on exit into a "low state" (extinguishing ). So this is a task for electronic engineers....

You could try a microwave detector, or use more detectors, covering the right areas.

makar42 wrote:

This is a room equipped with shelving,

.
It is a question of the correct positioning of the sensors as well as the number of sensors.
Large warehouse halls are also controlled by this solution with a sensor in each aisle, for example.
There are so-called aisle sensors with a more long and narrow field of view.
There are many off-the-shelf solutions.

And a solution with a photo barrier connected to a bistable relay fits your situation - only you can't see it.
The only problem is when different numbers of people enter/exit.

Hello .
Example of colleague Erbit's solution Link

@makar42 , arguments I think are completely misplaced. I think most of the solutions indicated above will work in this situation too. Starting with more accurate presence sensors placed in strategic places in this room. But certainly the solution indicated by Col. Erbit will also work. All you have to do is read with understanding and adapt the solution to the new conditions you point out only at the end .

Finally, it is difficult not to interject a small comment. I think that with such seniority on Elektroda you may have already learned that the problem is best described precisely at the beginning. It is hardly surprising that someone was not able to guess what the author had in mind AND whether the circuit is to be used in an ordinary loo, a secret room with shelves without doors or an atomic shelter, for example .

I am closing the topic.

In the so-called "meantime", I found a product on the web called LUNO7. Has anyone perhaps used this device ?