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Old magazine series 99 IC projects

Discussion in 'General Electronics Discussion' started by bertus, Feb 9, 2021.

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  1. ratstar

    ratstar

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    Aug 20, 2018
    In the 1979 one, I see a gizmo for a bar graph, and someone needed one for his water tank not long ago. =)

    It works with a strange technique of dropping voltage through diodes, but I dont see how it works entirely. Its actually an ADC! but you need one bar per bit, not one bit per power of 2 of the result, goes to show if all you need is 8 bit resolution ADCs sample as fast as you want, as long as you put the full 256 lines down.
     
  2. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    Did you read the text of the led bar graph?
    led bar graph 28 79.png
    When turning up the voltage, led 6 will be on first, then about 0.7 volts higher led 5 will turn on etc.

    Bertus
     
    ratstar likes this.
  3. ratstar

    ratstar

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    Aug 20, 2018
    I see, I was thinking it was a current dependant input! i see now. cool.
    You can exchange the diodes for voltage dividers, if your short on semiconductors. :)

    So does that mean you just put a current divider instead of a voltage divider you get the current version!?
     
  4. Nanren888

    Nanren888

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    Nov 8, 2015
    Diodes used to set voltage thresholds is not an uncommon technique.
    Here it would give a soft turn on, for each LED, I guess.
    .
    256?, OK :) with 256 LEDs, maybe 32,768 diodes, about 150 volts and 256 resistors, ratings for that voltage & quiite a lot of current.
     
  5. ratstar

    ratstar

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    Aug 20, 2018
    Pure Parallel does increase power requirements - but it would potentially give you sub pico-second sampling, if you handled all the other problems, which I'm not aware of yet.
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
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  7. TCSC47

    TCSC47

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    Mar 7, 2016
    Love these 99 cct books and others like them. When I was an apprentice and we were being taught valves (It was the 60s!) I got hold of a Practical Wireless, cct pocket booklet. I spent a lot of my time knocking up the transistor ccts and learning from them. Didn't get very good marks from my supervisors, but I found I knew a lot more about transistors than any of my apprentice colleagues.
     
  8. ratstar

    ratstar

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    Aug 20, 2018
    Maybe they were jealous.
     
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  9. bertus

    bertus Moderator

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  10. TCSC47

    TCSC47

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    No, I just didn't realise that I was supposed to do as I was asked to! You get wallys like me everywhere! Lol! Took me a while to figure this out. Mind you it enabled me to walk straight into a job after my apprenticeship.
     
  11. TCSC47

    TCSC47

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    Mar 7, 2016
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