overvoltage protection circuit problem!!!

Discussion in 'The Projects Forum' started by studystudystudy, Jun 4, 2010.

  1. studystudystudy

    Thread Starter Member

    May 21, 2010
    34
    0
    an my overvoltage protection circuit connect in this way?

    the voltage input, 'V in' go through the voltage regulator, which are Zener diode D7 series with Resistor R2 showing in the attachment. Zener diode D8 connect parallel with D7 and act as the protection or prevent of reverse polarity of voltage and current going through output.

    to consider the overvoltage, i add the thyristor parallel with D8, can it be connected in this way?
     
  2. Bychon

    Member

    Mar 12, 2010
    469
    41
    This is called a "crowbar" circuit. Well known among experts. It is well known because it works.
     
    studystudystudy likes this.
  3. Bychon

    Member

    Mar 12, 2010
    469
    41
    Oh yeah...you will need a triac instead of an SCR to make this work for both polarities.
     
    studystudystudy likes this.
  4. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    Your circuit will not work. :(

    The addition of another zener D8 in parallel to the original D7 has reduced the tripping point of your circuit to only one volt or a little more.

    Remember, a zener is simply a diode when used in reverse and permits current to flow to trigger the SCR.
     
    studystudystudy likes this.
  5. Bychon

    Member

    Mar 12, 2010
    469
    41
    I missed that one so badly! Apologies!
     
    studystudystudy likes this.
  6. studystudystudy

    Thread Starter Member

    May 21, 2010
    34
    0
    to eblc1388

    so i have to remove the zener diode D8, but what if i want additional function that can prevent wrong polarity voltage and current going through. i hope this additional function can grounded the wrong polarity
     
  7. Bychon

    Member

    Mar 12, 2010
    469
    41
    Go to ElectroTech chat. I just posted a schematic for you.
     
    studystudystudy likes this.
  8. studystudystudy

    Thread Starter Member

    May 21, 2010
    34
    0
  9. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    @ Bychon, why go to an other forum if you can post the schematic over here?

    @ studystudystudy, you can make two (contra mounted) circuits without the D8.

    Bertus
     
    studystudystudy likes this.
  10. studystudystudy

    Thread Starter Member

    May 21, 2010
    34
    0
    if my circuit without D8, then it will be a overvoltage protection circuit. this is what i found in the internet sample circuit. but i want additional function where i can ground the wrong polarity. so i decided to add the zener diode which is D8.

    sorry, i dont understand what is make two (contra mounted) circuits, is it you mean to have only D7 series with resistor, and parallel with thyristor. then make the same thing twice?

    thanks for you post reply, thank you very much
     
  11. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    studystudystudy likes this.
  12. Bychon

    Member

    Mar 12, 2010
    469
    41
    I was having trouble with PDF's on this site yesterday. All fixed today.

    I also thought the OP could look at the other site he posted on and find the answer...which he did.
     
    studystudystudy likes this.
  13. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    You can even simplify the circuit:

    [​IMG]

    Bertus
     
    studystudystudy likes this.
  14. Bychon

    Member

    Mar 12, 2010
    469
    41
    Yep. That works too.
     
    studystudystudy likes this.
  15. studystudystudy

    Thread Starter Member

    May 21, 2010
    34
    0
    thanks bertus,

    sorry, my understanding is low, despite the value of the zener diode or triac,

    is this simplify circuit can do following three function?
    1. voltage regulation - regulate the voltage
    2. wrong polarity protection - ground the wrong polarity
    3. overvoltage protection - ground the overvoltage occur

    i actually don't know how to interpret the simplify circuit you design, lol.
    i have to do more work on it.

    thanks again for bertus and bychon
    you both really help me a lot.
     
  16. Bychon

    Member

    Mar 12, 2010
    469
    41
    This is not a voltage regulator. It is an over-voltage detector, but you must already know that because you said that in the title of this thread. It reacts to excessive voltages of either polarity by shorting them to ground. You can not regulate a voltage by shorting it out.
     
    studystudystudy likes this.
  17. studystudystudy

    Thread Starter Member

    May 21, 2010
    34
    0
    to bychon

    thanks for advice

    i need voltage regulation function, reverse polarity, and overvoltage protection
    function, i attach a file, can it be like that?

    where D1 and R1 act as a regulator
     
  18. Bychon

    Member

    Mar 12, 2010
    469
    41
    With a big effort, I can imagine how that might be a voltage regulator for small currents IF you throw R1 away. R1 stops D1 from doing its job.

    It's more like this drawing.
     
Loading...