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Comparator and alarm

  1. Nov 19, 2013 #1
    I completed this circuit with 6 op amps LM741. Now I want to connect any high and low level alarm circuit. I have found and tried some solutions but I didn't get it to work. Can you give me some advice how to do it?

    Attached Files:

  2. jcsd
  3. Nov 19, 2013 #2


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    Staff: Mentor

    Welcome to the PF.

    What is the circuit supposed to do? You are feeding in a large AC signal -- what do you mean by high and low level alarms?

    BTW, there is a design error near the right of the schematic that will cause the circuit to become unreliable in a couple years after construction. Do you know what it is?
  4. Nov 19, 2013 #3
    U3 and U4's function has me scratching my head. I haven't seen that particular arrangement before. It looks like it might be a variation of an ideal diode feeding a peak detector.
  5. Nov 25, 2013 #4
    berkeman i'm curious what will make the circuit unreliable?
  6. Nov 25, 2013 #5


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    Staff: Mentor

    See the discussion about potentiometers and opamps starting at post #39 on page three of this fun thread:


    The thread discussed a number of "Bad Circuit" examples from the textbook "The Art of Electronics" by Horowitz and Hill. Let us know if the explanation in the thread (and the Bourns application note) make sense to you. :smile:
  7. Nov 25, 2013 #6
    Also asking for stability issues using the opamp's output to directly drive a coaxial cable to scope. Needs 10 ohms or so of series resistance. (Unless this is actually a scope probe).
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