Hi,

I need to build a proximity IR sensor (reflective) that detect human.
what IR sensor shall I use use to have maximum sensitivity?

IR Photodiode, or IR Phototransistor, which is best to use for my application?
what part number you suggest?


Thank you,
Victor

 

See the below sensor will it suits you? Actually it detects the motion not the body heat.

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Gayan

My Website
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Hi Gayan,
Sorry, not exactly correct.

The PIR [passive infra red], does in fact detect body heat.

But if the 'body' is stationary the heat is like 'dc' [background heat] to the PIR sensor.

The design of the lens and reflector cause shadows and bright bands of body IR to fall on the sensor IF the body is moving, so these are seen as 'ac' signals, which the PIR module reacts to.

Regards

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Eric
"Good enough is Perfect"

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Hi Victor,
As Gayan suggests a off the shelf PIR detector, IIRC Makro have them in stock.
I wouldnt recommend you try to build your own, the lens/reflectors are a bit special.

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Eric
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The sensor is to put on top of a entrance, purpose is to count how many people is passing though, to detect a few person pass though parallel, a few sensor will put in a line on top to cover. Hence I can' t use PIR sensor, as the detection angle is too wide (overlap), I need a more narrow detection angle for accurate counting.

I can't use camera solution for counting as the cost is too high to implement.

Thank you,
Vistor

 

hi,
This sort of request has come up on the forum many times.

Its very difficult to count people moving past sensors, especially if there is more than one person,
also to detect the different directions, in or out.

You will find that if people walk thru the PIR area when wearing wet clothing due to rain,
the PIR will not always detect them.

The other problem is when small children pass thru the PIR area, they are difficult to detect.

What you are going to need if you use IR, is a X,Y matrix of emitters and detectors connected to a MCU,
with some very fancy software...

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Eric
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Yes, this may be what I going to do, but I am not familiar with IR sensor/detector, what part I shall use for maximum sensitivity? I have read from other forum, to improve the detection range , a lens is needed, this is hard for me to get the suitable lens as well. So if I use a narrow angle IR Emitter and narrow angle IR Detector, do you think I can eliminate the use of lens?

Thank you,
Victor

 

hi,
Can you supply more details of the area thru which the people are moving.
Indoors, outdoors,, dimensions of the passage way ,, number and rate of people moving thru the space,, dark/light etc.

Its impossible to suggest a scheme without knowing the specification required.

Whats the purpose of the head count and how crucial is it no one is missed.?

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Eric
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Hi ,

Let me explain more in details, the idea is use on Home Automation, to switch on light or air-cond or anything.

If design use normal simple side beam sensor, or PIR sensor, the system can detect someone is enter, hence turn on lighting. But, when to turn it off? the system must detect the person is leaving . For example , If two person is enter living room, after a while, one is going out, the other one is still stay inside, the system won;t know there is still people inside, so by counting how many is in, how many is out, will be better solution.

May be someone will suggest putting PIR sensor at the living room to detect present of human, but PIR will not work if the humun is not moving. By other sensor like radar and etc, may not practical to install and cover whole living room.

So I come out idea on counting number of person in and out for the control, it just an idea only.

So, It shall use indoors, can be any size , depend on number of sensors. The environment can be light or dark, IR proximity shall be the cheapest solution as I think. (not consider camera)

Thank you,
Victor

 

If you have two sensors alongside each other. When a person passes sensor A and then sensor B, a person is entering. And vice versa for leaving. Two people don't usually pass through a doorway at once in the home.

 

hi Victor,
As its indoors you can use undercarpet pressure mats, [Maplins] they are not expensive.

I have them in my house for security and controlling the hall lights during the night.
They last for a long time, mine have been in operation for about 15 years.

They have a switch closure when stepped on, you could arrange two or more mats to detect direction.
If this wasnt sufficient you could have an hybrid system, say a knee high IR beam detector and pressure mat.

By using a PIC or other MCU it would be possible to make the detector system 'smart'.

There are two types, a square about 24inches and a rectangular stair tread type.
One at the top and bottom of the stairs switches a light timer on.

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Thanks Eric, you have provide an alternative solution.

Thank you,
Victor,

 

If you have an IR based exit/entry counter, you're in pretty good shape. You can use a PIR in the room as a backup in case there is a mistake in the count. (If the count somehow reaches zero, yet there is still movement, then the room is still occupied.)

 

Thats a simple safety net.

I think a hybrid system will be the way to go.

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Eric
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PIC tutorials:
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Bill's: www.blueroomelectronics.com/

 

VictorPS,

Did you fininsh your project? what did you used?