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Thread: How to generate bursts for IR Detection

  1. #1

    Default How to generate bursts for IR Detection

    Please help me....i can't get those bursts ??? I can generate 33Khz frequency through 555 but its continuous one ,how to make those with bursts ??

    I am not using any PIC.I have heard that the bursts can be produced through another 555 but how in which mode they should operate and what frequency it should generate ?

    I am using TSOP 1333 for IR detection.

  2. #2

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    use and gate with another 555

  3. #3

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    Thanks shobhitkukreti for your reply...but can you..explain it a little bit more.

  4. #4

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    Please read this http://www.roboticsindia.com/modules...ighlight=#8548

    Also take a 2 input and gate and couple both inputs of the and Gate with outputs of different 555. One will supply the 33Khz frequency signal, and other will provide the bursts. Please refer to the datasheet to check out the burst length. Since the other 555 will be at lower frequency than the main one which generates the 33khz freq, it will allow the 33khz frequency to pass through for some time depending on the burst length.

  5. #5

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    I tried a lot but its not working...I have used the circuit in the below link

    http://home.cogeco.ca/~rpaisley4/IrProximity.html

    the basic one with 3Hz pulse (556A) and 33Khz for 556B.

    but its not working....and one thing..when i align the IR LED in the direction of TSOP then there is a slight voltage variation but when used for objects i.e reflection of IR is needed the TSOP is not responding.

    What should I do ?? Is there any other way out for obstacle detection ?

  6. #6
    Administrator T-1000 vikas's Avatar
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    Use tsop 1738 , first time heard using anyone 1333.

    Generate a continues 38khz from 555.

    And use it for obstacle detection , no need for bursts ... it works just fine.

    Not exactly this ... but this might help

    http://www.electronicsforu.com/elect...ar%20Deterrent
    Vikas Patial

  7. #7

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    Thanks...Vikas for your reply..

    I have worked on TSOP 1738 when i first designed the circuit and hopefully..it was detecting..a continuous 38 Khz signal but when I tried to make the circuit once again with the same TSOP 1738 ,it was not responding(or you can very small i m saying very very..small change was detected)

    i don't know whether its sensitivity is decreased due to continuous 38 Khz when i experimented for the very first time.

  8. #8
    Administrator T-1000 vikas's Avatar
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    TSOP outputs a digital signal , there is no small or big . Just high or low.

    Incase a carrier is detected it goes low.

    Check ur circuit. Are ur emitters working fine , use a web cam to check ... and CRO to check if frequency is correct. Check if TSOP working ok , they easily go bad with incorrect connections etc.

    There are few things that can be wrong , just check the circuit.
    Vikas Patial

  9. #9

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    I have checked the frequency with CRO which is within the 38Khz bandwidth varying 37.XX to 38.XX so I think this part is ok.

    As far as the TSOP is concerned....how to check whether its working or not.

    The output goes low when it detects the IR for the very first time (when the IR is aligned in the direction of TSOP not any reflection stuffs..) and then the output remains high even if the IR is continuously aligned to the TSOP.

  10. #10
    Super Moderator T-1000 docel's Avatar
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    1. TSOPs dont respond to continuous 38khz signal. It will just output a momentary low and go back to high. This momentary low will occur with ordinary sunlight too.

    2. The correct operation of the TSOP is output LOW. This is a pulsing low, depending upon the 'burst' frequency.

    3. The TSOP is a very sensitive device. It will detect even low 38khz signals, from ALL directions, but the detection has maximum range from the built-in cylindrical "lens".

    4. Do NOT connect LEDs directly to the output pin. This will gradually fry the TSOP. You need a buffer, either a TTL/CMOS inverter or a simple transistor to drive an LED.

    Some Forums blatantly publish wrong information regarding the TSOP series. It is up to the user to decide if it is wrong or right, ofcourse. A through understanding of the Manufacturers datasheet is the right way to start.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

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