Occupancy sensor

Hello there,

The attached circuit is a motion detector which uses monostable multivibrator (e.g. CD4535) to trigger the relay for a predefined time if motion detected when someone entering or leaving a room.

I want to modify the circuit, when a person enter in the room a bulb turns on and remain in on state until the person leave the room. Do I simply put a latch circuit built around CD4013 and replace with monostable, so when a pulse received to the latch circuit it toggles the bulbs?

Your suggestion/help need to how I modify this circuit to fulfill my requirement.

Yes, a 4013 would work. Configure as a /2 where first pulse toggles it on and second pulse toggles it off.

Ron

Reloadron said:

Yes, a 4013 would work. Configure as a /2 where first pulse toggles it on and second pulse toggles it off.

Ron

Click to expand...

Dear Ron, there is another problem. The sensor must distinguish between a person entering and a person leaving, otherwise when the first person walks into the room the light will switch on, but when a second person walks in, the light will toggle again which result light will turn off, which not desired. So, do you have any idea to fix this problem?

This is a homework assignment on the old people counter problem. I suggest you look at the attached and work from there. Everything you need to know and understand is in the attached.

Ron

Reloadron said:

This is a homework assignment on the old people counter problem. I suggest you look at the attached and work from there. Everything you need to know and understand is in the attached.

Ron

Click to expand...

Ron, first I pay thanks to you for the help.

This technique is useful when there are two passages for in and out. In this situation only one door to enter in the room, so, If i replace photodiode with occupancy sensor, being a wide coverage area, both of them trigger simultaneously, which is not required so please help me if you have another idea.

If you look close at the circuit I posted and make sure the sensors are spaced about a 6 inches apart then both sensors do not trigger at the same time. Look at the logic. If a person enters the room one triggers before the other and if a person exits, the other sensor triggers first. So while yes, both will trigger, one will always trigger before the other. This allows a counter for example to count up (person enters) or count down (person leaves). Think about it.

Ron

Reloadron said:

If you look close at the circuit I posted and make sure the sensors are spaced about a 6 inches apart then both sensors do not trigger at the same time. Look at the logic. If a person enters the room one triggers before the other and if a person exits, the other sensor triggers first. So while yes, both will trigger, one will always trigger before the other. This allows a counter for example to count up (person enters) or count down (person leaves). Think about it.

Ron

Click to expand...

Ron, I think you will agree with me that to make project simple and reliable, putting a shutter placed in front of occupancy sensor will fix the problem. Because the shutter will open for every 1 minute and then closed, so it will detect presence or absence of someone and the circuit will trigger accordingly. Please give your expert opinion.

If I remember well, the passive infrared motion sensor has compartmentalized lenses and samples the images every second or so, triggering when the previous image does not compare with the last.
The solution would be to have a sensor with say 8x8 pixels, and memory in the circuitry. a few bits (32, 64...one for each compartment lens) At first turn-on, or when put in "learn mode", the circuit would save the 'image' of the vacant room and keep it permanently in non-volatile memory.
Switching into operation mode, the memorized image pattern would be compared to every sampling, triggering only when there is a difference. That would take care of non moving occupants.

Dear Externet, your idea is considerable but this will obviously make the circuit much complicated. Instead if I put the motion sensor in a motor so that the motion sensor will see the non-moving person in movement each time unless it find the room empty and will trigger accordingly.

Furthermore, i do not think that a PIR sensor has memory, instead it has two compartments which compares movement and delivers output.