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Bandpass filter help

Discussion in 'General Electronics Discussion' started by lucasfru, Oct 5, 2017.

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  1. lucasfru

    lucasfru Guest

    I'm currently trying to make 2 microcontrollers communicate using a laser laser diode and a solar panel.
    The problem I have is that I cannot manage to make serial data go from µc1 to µc2, a friend of mine suggested to use a bandpass filter but since I'm kind of a newbie in electronics and nobody I know irl seems to be able to help me I'm posting here...
    I want to make a 9.6khz bandpass filter, I dont understand the notion of gain, what should I use ?
    I have lm358's and lm324's at home, I would prefer to use 324 but any help would be appreciated !
    Thanks in advance!
  2. BobK


    Jan 5, 2010
    A solar panel is the wrong detector to use with a laser diode. You want a phototransistor. Or, better yet, you want device like the TSOP4838, which has the detector plus processing to recognize a specific frequency (38KHz for that part number) These are way better than what you would be likely to build.

    How far do you need to transmit? If not more than a few meters, a simple IR led would work. If not an IR laser pointed right at the detector would work. The emitter must be driven by square wave at the matching frequency.

  3. Audioguru


    Sep 24, 2016
    The lousy old LM358 and LM324 opamps have poor slew rate which causes trouble with frequencies above 2kHz. Instead use a more modern opamp that works fine up to 100kHz.

    Gain is the amount of voltage amplification. An active filter needs only a certain amount of gain so that it has sharp and steep filter slopes without oscillating.
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