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Can someone simulate this diagram for me please

Discussion in 'General Electronics Discussion' started by john2k, Jun 27, 2020.

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  1. john2k

    john2k

    174
    2
    Jun 13, 2012
    I came across the following diagram on the internet which is suposed to simulate the exact waveform a post catalytic convertor o2 sensor in a car does. I'm not too savy with this stuff and wanted to know if anyone is able to run a simulation of this exact diagram and show me how the output measures as a waveform over a period of time?

    One thing I don't understand is usually a LED has a resistor before it, so how is that first LED receiving full voltage and not blowing?

    Thank you.

    Here's the diagram below:

    beAR0Xh.jpg
     
    Last edited by a moderator: Jun 27, 2020
  2. john2k

    john2k

    174
    2
    Jun 13, 2012
    I think i've managed to create this diagram on LTSpice but i'm not sure how to run a monitor to monitor the output as a graph. If i click the man icon and type 1 in the stop time and then put cursor over the output i get about 970mV. I've uploaded the LTSpice file i created if anyone can help. Thanks
     

    Attached Files:

  3. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    Apart from an initial 0.5mS or so duration start-up current peak of ~700mA while the 22uF cap charges, the top LED passes only a few mA required mainly by the 555.
    Here's my simulation output. The voltage is dependent somewhat on the forward voltage drop of the particular LEDs used.
    555output.PNG

    Note: My sim time is 30S, not 1S :).
     
    Last edited: Jun 27, 2020
  4. john2k

    john2k

    174
    2
    Jun 13, 2012
    Thank you, the LED's suggested for this is [email protected]
     
  5. john2k

    john2k

    174
    2
    Jun 13, 2012
    What LED spec did you use to simulate getting 0.6V? in LTSpice i cannot seem to be able to add a 1.7V 20mA LED .
     
  6. Ylli

    Ylli

    324
    84
    Jun 19, 2018
    Try this, add a spice directive:
    Annotation 2020-06-27 124334.png
     
  7. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    NSCW100 (one of the LEDs in the default LTS installation).
     
    Last edited: Jun 27, 2020
  8. john2k

    john2k

    174
    2
    Jun 13, 2012
    Thank you. It seems that if I try and use a [email protected] LED then the high end of the voltage is just over 0.7V but if i use a higher forward voltage LED then it drops the voltage. Also, is it correct that if I change the 1M ohm resistor to a higher value then the switching time will increase and if I decrease it then it will decrease? So right now with the 1M ohm resistor its about 3 seconds, if i increased to 2M ohm then this time will extend to possibly double and if I decreased it by half then it will half?

    And the 10K ohm resistor just before the output, that seems to effect the voltage output. So whatever LED I choose, once I have the LED on there and if I wanted a certain voltage output then I could adjust that 10K ohm resistor right?
     
  9. narkeleptk

    narkeleptk

    21
    9
    Oct 3, 2019
    I was thinking of using this same schematic for some o2s simulation but never get around to testing it out. If you do try the real thing, let me know how it works out for you.
     
  10. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    Yes.
    The 10k affects the output voltage, but I don't know what you mean by 'a certain voltage'.
     
  11. john2k

    john2k

    174
    2
    Jun 13, 2012
    For example in your graph with a NSCW100 LED you were getting the high peak voltage of just above 0.6V and low of 0.0V. If I wanted the high peak to be 0.7V and the LED i used doesnt give me that, then technically swapping that 10K resistor should allow me to make slight adjustments right?
     
  12. Ylli

    Ylli

    324
    84
    Jun 19, 2018
    Tweaking either the 10K or the 100K on pin 3 will change the output voltage. If you want to increase the output voltage, increasing the 10K or reducing the 100K would do that. Personally, I'd reduce the 100K and leave the 10K alone.
     
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