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Whats inside a IR reciver? — Parallax Forums

Whats inside a IR reciver?

stig2stig2 Posts: 5
edited 2006-03-14 13:32 in General Discussion
as I understand it a IR reciver is a photodiode and a IC that does some comparison..

anyone know if this IC function can be replaced by another IC, and then be connected to a larger number of photodiodes?

datahsheet on a recviver.
http://www.elfa.se/pdf/75/07520596.pdf

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-03-11 17:31
    This post is being moved from the Projects Forum to the Sandbox Forum.

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    Parallax Tech Support
    csavage@parallax.com
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-03-13 14:30
    The problem with IR is that you can have it modulated at many frequencies. If the receiver were for a wide open reception, the IR from light bulbs would insert a 50 or 60 cycle hum and so on.

    So much like the same problems in AM radio, the IR tuned into a band [noparse][[/noparse]about 38500Hz, though some manufatures vary this upward toward 41,000Hz].

    So what is inside. A IR receiving diode; maybe a sheilded case to receive in one direction, and a band-pass filter. I suppose there might be an amplifier too.

    So, you would need an op amp arrangement as your filter and you would need to get enough power out of it to be useful. Personally, op amps are something I don't really like to work with, but it can be done. An osilloscope would help you assure adequate filtering and adequate output [noparse][[/noparse]I don't have one].

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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

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  • stig2stig2 Posts: 5
    edited 2006-03-13 20:59
    ok. So my idea of saving component costs by replacing the more costly IR Recivers with dark photodiodes and only a singel IC or a Microcontroller is not such a good idea, since I will need a op-amp + amplifier + diode.. = 3 components ??

    I thought that a photodiode plugged into the I/0 of a basic stamp could recognise a osilated signal like 38,5 khz from the background light/noise? I have many photodiodes, and they are hard to use as a dark /light sensor. What are their purpose in life?
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-03-13 21:42
    stig2,

    Probably more than 3 components.... There are also more than likely a couple of components, RC or LC or both, that form a filter on the front end specifically
    tuned to either block or allow specific frequencies in the desired IR frequency range.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • stig2stig2 Posts: 5
    edited 2006-03-14 13:27
    thx. I will stick to the IR recivers instead, they are also easy to use.
  • bobledouxbobledoux Posts: 187
    edited 2006-03-14 13:32
    Google "PNA4611" to read the Panasonic datasheet for their IR receivers. They display a block diagram of the receiver. It includes an amplifier, automatic gain control, peak detector, comparitor, and more.
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