Does a "real" presence sensor exist, or are all PIRs motion-based?

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I want to add a presence sensor to my bathroom.

I know you can get a standard PIR sensor with a timer delay, however these still turn off if you are in the room but remain still after the time delay elapses.

Does such a thing as a real presence sensor exist? I.e. one that would remain on for however long a warm body is in the room, despite not moving? Or are they all motion-based?
 
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Have you thought about having a manual switch which people can use as appropriate when entering or leaving the room?
 
Yes, I wanted to try something more adventurous though! Does this sort of thing exist?
 
Never soon one suggested whenever people have asked here (and they often do) about the utterly bonkers idea of using a PIR because a switch which never goes wrong, never turns the lights out when people are still in the room, and always allows people to have perfect control over turning things on and off, is not adventurous enough for them.
 
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All PIRs are movement based, as they compare the background level of the location to any moving objects which have a higher heat (IR) output.
 
Do you know if an alternate sensor type exists that could achieve this?
 
There are all sorts of sensors, breaking a beam, colour, but the industrial sensor often have a price tag which you would not want to pay. Paying £200 for s sensor is not unknown. And £200 is cheap for anything to replace a man. Many are 4~20 mA so you likely also need some sort of PLC to read the sensors output most are 24 volt DC not 230 VAC so it needs more than the sensor.

Likely the cheapest after a PIR is a pressure sensor. But if for example you were wanting something to show the bath is in use then likely temperature would be a good method. Room is unlikely to exceed 25°C but that would be rather cold for a bath so set to turn on at 25°C will likely work. In industry we often use more than one sensor and use programmable logic control. (PLC) So flow sensors, temperature sensors may all be used together.

The automatic flush systems used at airports, movie theaters, and restaurants all use active IR technology, not PIR. Active IR uses an IR transmitter and an IR receiver. There is one sensor per toilet.

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They are located behind the toilet seat (or on the top of a urinal) and bathe the immediate area with IR light. When a person enters this field, the IR bounces back to the IR receiver and after a few seconds "arms" the unit. When the person leaves, after a couple of seconds the control unit flushes the toilet or urinal.
I know in shops they worry about some one hiding in the toilet until the shop is empty then coming out to help them selves. There is an issue using cameras so some other method is required. But it's not cheap.
 
i do wonder if a PIR that was mounted on a swivel and oscillated a few degrees from side to side would see a stationary heat source as moving and thus activate. In theory it should work as the heat source would appear to be moving from sector to sector in the images in the PIR.
 
If you wan to be adventurous in the toilet, try peeing in the dark and see if you can hit the pan.
 
How about a whistle (or "wind") audio sensor then as you are tinkling the china your presence could be detected by the dulcet tones of whatever tune you choose. I'm sure there are "gas" sensors that could also be used.
 

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