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  1. #1
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    photodiode with ir filter

    what is sutiable material for covering ir photodiode and ir led used in proximity detector ckt.
    for following purpose without affecting operation like range and sensitivity

    1> protection from dust and humidty
    2> protection from changes in ambient light
    3> protection from bright light if it will fall on photodiode it will suprress the ir signal

    ir photo-diode and ir led are place near to each other and seperated by a metal partition
    and also in some ckt ir photodiode is replace with TSOP1738 ir reciever module from vishay.

    i have seeen in vishay modules range increases as brightness of light in surrounding decreases.
    and this is undesirable for us

    •   Alt14th July 2006, 08:58

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    ir photodiode or phototransistor sunlight

    In order to provide the protection againt bright light- such as light from sun,
    tube light etc, it is better to use modulated ir light(with LEDS) and photo transistors which have frequency dependancy. Thus it is possible to
    filter out noise voltages from other natural and artificial sources. Photodiodes
    do not have freaquency sensitivity.



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    photodiode cover

    what about biasing the biasing point will change with change in intensity of light.
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    •   Alt14th July 2006, 11:15

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    biasing tsop1738

    The biasing point will not shift . Only a small current will be the
    at o/p of transistor. Use filter and amplifier to avoid low freaquencies
    and to obtain a required voltage and current from ckt.



    •   Alt17th July 2006, 02:48

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  5. #5
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    ir photodiode sunlight

    i am using TSOP 1738 from vishay in which we are using modulation first of all carrier is 38Khz and on it we are sending 1200bps signal. so its modulated already.

    when i switch off my tube light i get more range which is undesirable.
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    led ckt with photodiode

    i think your IR detector(modulaor) is not working properly. As i have used an ordanry IR detector module, there is no any problem.
    tell me how much % rang is reduced when tube light is placed on that?
    if it is about 10% or less. that is no problem if it is more, then replace IR detector module.



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    photo diode bright light

    Hi,

    here is the article describing the use of fully exposed
    and developed photographic film negative as cheap ir filter
    (it is dark = no visible light, but still quite transparent to ir)

    h**p://geektechnique.org/index.php?id=254



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    range of ir photodiode

    Quote Originally Posted by Noman Yousaf
    i think your IR detector(modulaor) is not working properly. As i have used an ordanry IR detector module, there is no any problem.
    tell me how much % rang is reduced when tube light is placed on that?
    if it is about 10% or less. that is no problem if it is more, then replace IR detector module.
    I think this is likely the case. Last spring I used the Handyboard for a school project involving IR obstacle detection, using two different IR detectors. One worked the same regardless of lighting (inside or out), but the other had some seriously reduced range (up to 75% decrease) whenever in bright sunlight, or flourecent lights. Replaced the one module and everything worked as it should.



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    ir obstacle detector using tsop 1738

    Noman Yousaf: I am using tsop1738 most widely used ir detector.

    blue_snake: idea is good i will surely check that out.

    Bigestlee: which modules u were using
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