I want to do mini project on automatic fan system using LM350 and PIR Sensor
I need Circuit design

 

Welcome to AAC!
What sort of fan? Mains driven? 12V computer fan? ....?
Which PIR sensor?
Links to datasheets for the fan and sensor would be helpful.
What 'automatic' functions do you want?

 

Welcome to AAC!
What sort of fan? Mains driven? 12V computer fan? ....?
Which PIR sensor?
Links to datasheets for the fand and sensor would be helpful.
What 'automatic' functions do you want?

HC-SR501 PIR Sensor
12V computer fan


Function :The Fan should operate when the temperature is greater than normal in the presence of person inside room.

 

The PIR won't detect the presence of a human, only the movement of a human. If the human is sitting still the PIR won't know they are there.

 

The PIR won't detect the presence of a human, only the movement of a human. If the human is sitting still the PIR won't know they are there.

Any other suitable PIR sensor

 

Any other suitable PIR sensor

There have been lots of threads on these forums related to detecting (or in many cases, counting) humans in a room. It's never straightforward.

I doubt there's a one-sensor solution - unless maybe you're thinking of using video or thermal imaging in conjunction with a microcontroller and a LOT of programming!

I'd recommend thinking of other ways to determine when the fan control is active. Does a person in the room always have the lights on, so you could work based on the lights? Are you only really interested in running the fan when the person is sitting in a certain spot, so maybe you could use a pressure or strain sensor to see when they're in the seat?

Alternately, is it ok to accept the limits of the PIR system? You could have motion trigger a timer, so you get 15 minutes (or whatever time you choose) for each human action, then the system stops. If the person is still in the room and still wants the fan, they have to wave their arm to re trigger the system.

The temperature part is easy - in all the scenarios above, when I say the system is active, I mean the thermostat controls the fan. When the system is inactive, the fan/thermostat are off regardless of temperature. If you decide on a human detection scheme that's plausible, adding temperature to the mix won't be hard.

 

One "gate" sensor per entryway. It will prove concept. A vertical line of gate sensors per entryway...with a processor is much more sure. You can keep track of occupancy with hard to fool gates. A zigzag vertical line.