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  1. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    OK I understand now that the process of charging/discharging is the same but the difference is when using it with AC or DC.

    One case of AC use is that it could charge/discharge from both sides....
  2. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    I really appreciate your practical demonstration as I actually all my work is done with simulation :)



    Is the circuit the same one as this ?
    ...
  3. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Hi,

    I'm working on this simulation.

    I just have a question about the best way to measure the gate voltage and thus calculating the gate current.

    158614

    Is it enough to measure the rms...
  4. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    The signal appears to be really stable. So this would a very/low cost oscillator for a lot of electronic systems. Where could this oscillator be used and how famous it's in current designs ?

    - - -...
  5. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    OK that's really good to know.



    This is my next task to do.


    But there's a problem in this regard which is that I can't control the amount of voltage that goes to the gate, thus I can't...
  6. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yep, it should work in reality. But I believe the simulator didn't cover this effect.

    I found it here:
    http://www.bristolwatch.com/ele/diac.htm

    It's the diac relaxation oscillator, there's...
  7. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    OK, I only got one pulse, then it continues to have 22V output.

    158591

    I just changed the capacitor value, to have more obvious charging time.

    It charges until 42V ti drop to 22V...
  8. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Here's another simulation I did, and I think the diac here is continuously in conduction mode, the effect of oscillating as Brain told me that it should happen but it isn't so I think the simulation...
  9. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yes because 100 V - 68.5 V = 31.5 V which is less than minimum break over voltage which is 35 V but it is close.

    So the diac would break any time the voltage across it is from 35 - 45 V.


    ...
  10. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    I tried, it's the same. I put the capacitor voltage at 45V as maximum DB4 VBO is 45V.

    158556

    - - - Updated - - -



    I could observe the diac effect as a voltage clipper. In this circuit I...
  11. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    I actually did exactly as he said, see 2nd line of #69, he said the schematic is correct, then he also told me to try 100k. So I did two circuits one with 1k (yes it's not 10k because I already did...
  12. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yes I understand the scr is a current driven device.

    Like BJTs are current driven transistors where MOSFETs are voltage driven. So scr firing is about current amount, and the discharging is the...
  13. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Highest current rate possible, if the voltage is so high it could cause a high current spark.
    When I work with PC power supplies, I use like 1k ohm/1W resistor to discharge the high voltage...
  14. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Of course not, I actually learned a lot. Like I thought about the last information you told me that the resistance has to be very low, so I removed the unnecessary resistors and kept the overall...
  15. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    OK, I think I learned something.

    158534

    I simplified the circuit more, no need for all those voltmeters, because they give rms value. I can now know what's going on with the scope.

    In this...
  16. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Hi,

    I modified the circuit a bit.


    1. Measuring the signal at the gate, is negative with one scope probe. Why ?

    My understanding here, is that the AC has two branches to run in. Path 1 is...
  17. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    oh yeah .. thanks :)

    really fundamental things.

    I really should have thought of that .. it's an ac signal. And the value in the voltmeter is the rms value ! It's a huge different thing !

    One...
  18. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yeah, first I get the warning, but after some time I get the fatal error.

    I know that there are differences between the real and simulation, but I think warning means that there is something not...
  19. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yep I did it !

    158505

    But:
    1. I can't get the scr to full conduction.
    2. I get simulation warning.
    3. Gate current is 10mA where it should be > 50mA.
    4. After some time I got simulation...
  20. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yes that's correct and I'm putting two simulations side by side, one has the load on anode and the other on the cathode.




    Because of scr output.

    With load connected on cathode, I get the...
  21. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    I didn't understand that completely, it would take me time to understand specific process of triggering the scr.



    I think I go the idea, that it's about the time of charging the capacitor and...
  22. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    How about these ones I found on Aliexpress:
    ...
  23. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    I want to know the type of the capacitor ? is it ceramic, electrolytic, polypropylene .. etc ?

    There are cheap caps on aliexpress that work on high voltages +240V.




    Yep I know that I know...
  24. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Yep, OK but when I don't put a ground the output signal doesn't clear any sense and really different than anything know about rectifiers.



    yeah .. well ! I don't know almost all circuits that...
  25. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    I followed a method on this website, and it worked but I think there's something different about Proteus simulation.

    https://www.electronics-tutorials.ws/power/thyristor-circuit.html

    I works...
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