Create an IR sensor to switch on and off lights when someone enters or exits the room

[gursi11594]

I am planning to build an IR sensor to automate the lights. What i am planning to do is to place to IR emitters and two IR detectors parallel to ground and to each other such that both don't get triggered at the same time. What i need is that if i trigger the first IR first and the second IR second then it should switch on the light ( that means i entered the room), and if i trigger the second IR first and the first one after that( means ive exited the room), it should switch them off. Any suggestions? i would like to avoid any PCBs or programmable microcontrollers and use only simple relay kind-of circuit.

 

[Magnatron]

hmm use something kind of this.. (simple one)
IR emitter >------> *DOOR* >------> IR receiver >-----> trigger circuit using 555 Timer (monostable) >---> clock signal to a Flip Flop >---> relay diver (transistor) >-----> relay.
or search Circuit lab, diagrams,Free circuits, Electronics periodical, e-mags: India

 

[freddyp007]

Hi,

You can use TSOP1738 IR receivers. They are easily available and are commonly used in TV remote control receivers. But they are excited only by an IR radiation of frequency 38kHz. So, you also need a 38Khz astable oscillator using 555 timer.Refer the following circuit for emitter. For that entry and exit thing try using a flip-flop as Magnatron suggested.

 

[ard]

I would suggest PIR modules, the kind that come with a plastic fresnel dome. Very easy to wireup, and the output goes active when the module sees motion. They also come with a small trimmer for a built-in adjustable timer that keeps the output active for a delay *after the last sensed movement*. This way, you dont have to actually the monitor the door for incoming-outgoing traffic.

Regards,

Anand Dhuru

 

[gursi11594]

hmm use something kind of this.. (simple one)
IR emitter >------> *DOOR* >------> IR receiver >-----> trigger circuit using 555 Timer (monostable) >---> clock signal to a Flip Flop >---> relay diver (transistor) >-----> relay.

So basically what im doing is when the beam is trigerred the flip flop( or latch, is that correct?) switches the lights to on and they stay on until the beam is trigerred again. IS that right?
i have a couple of questions-
1) what is the use of a 555 timer in this circuit??
2) i need the lights to remain lit such that any number of people enter the room, it does not switch off, and switches off only when someone exits the room. can this be achieved?

You can use TSOP1738 IR receivers. They are easily available and are commonly used in TV remote control receivers. But they are excited only by an IR radiation of frequency 38kHz. So, you also need a 38Khz astable oscillator using 555 timer

Your reply has triggered another plan in my mind. i can place a detector somewhere and use an infrared battery powered remote as emitter. Is it necessary to convert the radiation to 38khz? i can directly shoot a single beam of IR to the reciever and i need only lights to be automated. This plan can even rule out the error of lights closing accidently due to one person going out of the room, when i am still sitting inside. ( I can imagine myself screaming at him. )
What accourding to you would be a better plan? to fix the emitter and the detector at the entry or use an ir remote?

I would suggest PIR modules, the kind that come with a plastic fresnel dome. Very easy to wireup, and the output goes active when the module sees motion. They also come with a small trimmer for a built-in adjustable timer that keeps the output active for a delay *after the last sensed movement*. This way, you dont have to actually the monitor the door for incoming-outgoing traffic.

But that would even trigger the circuit if i pass by my room, as the link said it detects change in IR lever. another problem i could have is that when i am sitting in the far end of the room, away from the sensor, it would feel that no one is there so it would switch on the lights.


Ive decided that ir remote would be a better option as i can also use it when i want to watch a movie to switch off the lights automatically. What are your opinion on this regard?

 

[Magnatron]

i think this may solve all of the issue..
**broken link removed**