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3.3v Analog Input question

Discussion in 'General Electronics Discussion' started by GonzoEngineer, Dec 18, 2011.

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  1. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
    I have a microcontroller that is powered by 3.3V and I need to read an analog signal that is also supposed to be in the 0-3.3v range.

    I have a LEM current sensor that puts out 4V at 100 Amps. (70 Amps is hopefully the highest current reading I will have, but we all know better than that.)

    The problem with the LEM, is it will also put out 8V at 200 amps, and even higher.

    Can I just use a 3.3V zener to make sure the signal into the microcontroller never exceeds
    3.3V?

    Is this the best way to do it?

    Any ideas would be greatly appreciated, this is the last part of the circuit I have to work out. All my digital signals into the board are 15V, so I am just using optoisolators to convert the levels.

    If anyone has any good advice on this, I would surely appreciate it.:D
     
    Last edited: Dec 18, 2011
  2. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,264
    2,717
    Jan 21, 2010
    Yeah, tips 10, 11, and 12 are something like what I would have suggested as possible options.

    Another thing to keep in your bag of tricks is this. Whilst overkill in this case, you may find it useful in more complex cases.
     
  4. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
    Thanks for the reply...and the link!

    That is a better approach than what I had for the digital signals..:D:D
     
    Last edited: Dec 18, 2011
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