4 Comments

  1. Brandon
    31. May 2017 @ 5:34

    Great video thanks so much. I have a couple questions. At 10:00 can I assume you doubled the capacity of the bottom capacitor (as per your diagrams)? And that you only had one protection circuit on the top capacitor?

    Because the zener is not providing enough current to the bottom large capacitor, too much is still going to the top one. That results in the top (smaller) cap having an over voltage. Is that correct?

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    • admin
      23. June 2017 @ 10:16

      1. Yes
      2. The zener has no clear cutoff voltage. Therefore, it allows voltages above the 2.7 volt (because its resistance is too high).

      Reply

  2. Nathan Bryant
    9. October 2017 @ 23:55

    Hello. Thank your for making excellent videos. I think your schematic for the board might still have an error. It seems like it makes sense for R3 to be in series between the cathode on the TL431 and the base of the PNP transistor (Q1). That limits the current through the TL431, which then limits the current through Q1. Otherwise, it is possible for Q1 to see more current than the load resistors (R4-R6)

    Reply

    • Nathan Bryant
      10. October 2017 @ 0:39

      Hmmm. When I wrote the comment above, I was playing with a simulation where I replaced the TL431 with a simple switch I could open and close to see the behavior, but the real circuit doesn’t work if it is modified like I described. It seems like the cathode must be tied to V+ with a resistor.

      Reply

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