want ask for suitable motion sensor

[delifadzli]

Hi everyone, I want to ask...what is the suitable sensor to detect human.

The scenario, the sensor will detect the human as he/she enters the room. The sensor somehow will act as switch off / on. This sensor will be combined in my temperature sensor- fan circuit. So, as the human being detect, it will allow the temperature sensor to operate. If not, overall system will be off.
Then, how to make detection became reliable as the human still exist. For example, the situation where the user is sleeping (no motion). How to make the overall system still operate.

Please someone help me...any idea???

Hope for your respond.

[Jerson]

One possibility

Use 2 IR beam interrupt sensors to detect entry/exit into/from the room. Every entry into the room will increment a presence counter. When presence counter is not zero, you could keep the AC on. When everyone has exited the room, presence goes to zero and the AC can shut off.
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Regards
Jerson Fernandes

[Ttelmah]

Scenario #1, easy PIR.
Scenario #2, almost impossible. No motion, Bit of heat, but this could be coming from a piece of electrical equipment left 'on'. Capacitance changes, but these again could occur from things left in the room (this is commonly used around moving equipment, to detect when somebody 'enters' a danger area, but here the equipment in the area is tightly controlled, not the 'movable feast' of a normal room...). Only one that has much hope, is a gas detector system, looking for the CO2 being exhaled. This is how 'stowaways' are detected on trucks etc., at border crossings, but even then, the most reliable system, is often a dog...
Other system being used is humidity (exhaled damp air), but this has problems with things like tropical fish tanks.
Consider 'counting' entries/exits instead. If you know somebody has enetered the room, and not left, then assume they are still inside.

Best Wishes

[temtronic]

#2 can be done with two additional sensors per door. These sensors are 8-10 inches apart and detect whether the human is coming into or leaving the room. A state machine can be constructed to determine if someone is in the room. Think of how a 'quadrature encoder' works.Obviously you have to account for more than one person, again easy to implement.
Theme parks use a similar method to count how many are 'ready' to see the next show, easier as they have one count for in, one for out. That's why you need two sensors on your door.
It gets a bit more complicated for multiple doors as people can come in one door and out another, but really not that difficult to code.

[sjb]

[SherpaDoug]

Depending on circumstances, counting people going in vs coming out could be problematic. What if someone stands in the doorway? What if someone sticks their head in to see if the room is occupied and then backs out? What if they are pushing a cart or pulling wheeled luggage? Children? Dogs? There are lots of odd cases to consider.

Would it be possible to put RFID tags on people? Could you weigh the room?

Tell us more about the application.
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The search for better is endless. Instead simply find very good and get the job done.

[Jerson]

This reminds me of a tunnel occupation counter I built "once upon a time ...."

It had to solve the problem of deer, yes deer, running through the tunnel. So, we used IR beam interrupters placed further apart than a fully grown deer. Proper knowledge of the problem can help find an optimum solution.

A simple idea could be to use a switch to catch the door opening and confirm it by a beam interrupter. This way - if a person is going into the room you will see door->IR and the other way around for exit, you get IR-> door. 4 legged animals do not open door locks - or do they now? lol ;)
_________________
Regards
Jerson Fernandes

[delifadzli]

Thanks for the response...especially for the suggestion and tips ....in this case, I'm quite interested in using PIR sensor.

Here, I just want a little bit explanation of how to implement the sensor with PIC 16f877a. To solve that problem, need to use 2 sensor per door? for what condition?... Then, am I need to used AND GATE or OR gate...?

And for the problem that you all had provided like the heat concern and the others ... is quite good. Thanks very much.

But for now, I'm planning to solve for just to make the fan work as the human being detect and also to maintained the condition still work if the the motion like "sleep" is happen.

Sorry for my english and my weakness for this problem. I am actually quite new toward the PIR sensor...isn't this sensor too complex to use??

[newguy]