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Design 3-step sequence circuit.

Discussion in 'Electronics Homework Help' started by asdffdsa, May 30, 2019.

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  1. asdffdsa


    May 30, 2019

    I have a question regarding designing 3 sequential circuits using an op-amp, diode, and transistor. Question is described below.

    The circuit is a comparator that supplies a 3-step sequence of output signals.
    The circuit should behave in the following manner.
    * Pressing S1 (Switch) discharges C1 and lights LED 1 (and LED 2 briefly).
    * C1 then charges through R4.
    * As charge on C1 passes 3 and 6 volts, LED 2 and 3 glows in sequence.
    * Reduce R2 to balance time delay sequence and reduce delay time.
    * Delays shown will vary with tolerance of C1.
    Need to use the following IC components:
    · LM1458
    · 2N2222
    · 1N914
    The power supply of the circuit is 9V DC
    LED 1 is Red LED
    LED 2 is Green LED
    LED 3 is Blue LED
    You need to use and calculate the values of the following components for the circuit.
    Ø Potentiometers, or Variable Resistors
    Ø Resistors
    Ø Capacitors

    Help would be appreciated.

    Thank you,
  2. AnalogKid


    Jun 10, 2015
    We help those who help themselves. Please post your schematic. To aid the discussion, be sure to have a reference designator for each component (R1, C1, etc.).

    hevans1944 likes this.
  3. BobK


    Jan 5, 2010
    What a strange assignment. You have no schematic, but it refers explicitly to components, as if you did.

  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    In case this is still an active topic:
    The magic word is "window comparator" (o.k., 2 words).
    Timing is to be adjusted by setting appropriate thresholds. Obviously part of the circuit has been given to you (how else could componnet identifiers be referenced). Upload this part of your schematic (if you get an error message, reduce the size of the image).
    The part you have is obviously critical for the timing. Do you recognize the circuit? What is the characteristic of output voltage vs. time? Show us your analysis.
  5. asdffdsa


    May 30, 2019
    I haven't given any circuit or schematic. This is all my question. I know how to make a sequence circuit using transistor and diode but, the op-amp is making me confuse and i am not getting it properly.
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Then show us your circuit, how else do you think we can guess what are components like C1, R2 etc?

    The Opamp will be (ab)used as a comparator, not a linear amplifier. Look up "window comparator", that's what you are going to need here.
  7. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    You claim you know how to make a "sequence circuit using a transistor and a diode." Show us your schematic with parts call-outs and your explanation of how it works. A picture of a hand-drawn schematic is okay. Someone here will look at it and ask more questions. Until that happens, you answer our questions. As Harald said, "show us your circuit." Otherwise, you are just wasting our time. Also, this does not look like legitimate homework and probably needs to be moved to another forum.
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