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  1. #1
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    8051+ir interfacing

    Hi,
    I want to make a security system for a room using IR. My job is when a man enters in the room IR detects it. But i never use IR before.

    How can interface a IR detector and IR emitter with microcontroller so that I can detect inturrupt beteen IR detection?

    Please suggest me and give me few links related to this topic.

    Thanks a lot.

    •   Alt2nd August 2006, 01:28

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  2. #2
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    pir lm324

    First you will need a PIR detector, like the ones used on alarms and such (http://lib.store.yahoo.net/lib/webtronics/kit62pir.jpg), normal ir detectors won't do.
    Some schemetics for this are available here
    http://www.geocities.com/archilochus...ges/sensch.gif
    http://www.discovercircuits.com/S/s-motion.htm



  3. #3
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    ir microcontroller

    I didn't understand. Why do I need PIR? Why can't I interface simple IR detector?



    •   Alt6th August 2006, 04:11

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    ir sensor interfacing with 8051

    PIR sensor detects human by the heat produced from the human body. Suppose if someone else except human came, then Ir will detect, PIR won't. Connect IR LED to 5V through some 330ohm. Other side u use Photo Diode with LM324 comparator to detect, but this has range of 5-7cm only. For long distance use TSOP1738 sensor and 38Khz modulated IR. sometime u can use sonar, but u better go for PIR+TSOP combination.

    See some distance measurement techniques. TSOP can detect 1m and sonar is also 1m or more

    see these
    Infra Red LED-http://booksbybibin.14.forumer.com/viewtopic.php?t=28
    DISTANCE MEASUREMENTS-http://booksbybibin.14.forumer.com/viewtopic.php?t=115
    light sensor: PHOTO DIODE-http://booksbybibin.14.forumer.com/viewtopic.php?t=127
    light sensor: PHOTO TRANSISTOR-http://booksbybibin.14.forumer.com/viewtopic.php?t=128


    COMPARATOR USING OPAMP(LM324)-http://booksbybibin.14.forumer.com/viewtopic.php?t=37

    Bibin John
    www.bibinjohn.tk


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  5. #5
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    photodiode microcontroller

    OP was talking beam break detector, those are other types..

    For beam break you just modulate IR LED on one side, when receiver doesn't see it something is in the beam. Easily can do 20 meters. Not a good alarm since it's easy to defeat, but fine for people counting or detecting. Used on a lot of garage doors near the floor as an object sensor, break the beam while the door is going down and it goes back up.

    Radio Shack used to have one for a long time for a door chime/alarm that had a sensor and IR sender in the same unit, and just a reflector for across the room on the other side to bounce the beam back. Most Radio Shacks had one set up at the front door for years. Never sold well and they dumped them a few years ago, now most of their door sensors are just the magnetic type.



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    interfacing ir sensors with microcontroller

    you can also use an IR detector module using a photodiode on one side and an IR led on the other. When someone enters the room then the IR signal being received by the photodiode will be interrupted and this activity can be monitored though a microcontroller. A PIR detector on the other hand is expensive and is supposed to be used in application having larger monertary support or precise environment.



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    interfacing of ir with 8051

    Just to mention, PIR stands for "Passive Infra-Red", since no one mentioned it here. :D


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