+ Post New Thread
Results 1 to 9 of 9
  1. #1
    Full Member level 2
    Points: 986, Level: 7

    Join Date
    Dec 2014
    Posts
    143
    Helped
    3 / 3
    Points
    986
    Level
    7

    Confused between 2 terminals of Triac

    Hai , iam building a AC dimmer circuit using Triac, When going through all the available circuits online, iam confused between 2 forms..

    In some of the Circuit, the input AC Line is fed to Main terminal 2 of the Triac and in some other circuits Load is connected to main terminal 2 and Ac line is connected to terminal 1.

    Which is the best possible result??

    Click image for larger version. 

Name:	circuit 1.jpg 
Views:	34 
Size:	71.4 KB 
ID:	134339Click image for larger version. 

Name:	circuit 2.jpg 
Views:	25 
Size:	38.5 KB 
ID:	134340

    •   Alt9th December 2016, 13:45

      advertising

        
       

  2. #2
    Super Moderator
    Points: 227,400, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    39,187
    Helped
    11974 / 11974
    Points
    227,400
    Level
    100

    Re: Confused between 2 terminals of Triac

    Both circuits have the opto triac between A2 and G, in so far, they are connecting the triac in the same way. Circuit 2 has an additional filter suppressing fast pulses that might trigger the opto triac.



  3. #3
    Full Member level 2
    Points: 986, Level: 7

    Join Date
    Dec 2014
    Posts
    143
    Helped
    3 / 3
    Points
    986
    Level
    7

    Re: Confused between 2 terminals of Triac

    Quote Originally Posted by FvM View Post
    Both circuits have the opto triac between A2 and G, in so far, they are connecting the triac in the same way. Circuit 2 has an additional filter suppressing fast pulses that might trigger the opto triac.
    Oh,, i guess iam missing some knowledge here, Iam new to Triacs and analog circuit. But what confused me is in the diagrams above in the first one Load is connected to top part and input line is connected to bottom,, but in the next circuit it is vice versa.



  4. #4
    Super Moderator
    Points: 227,400, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    39,187
    Helped
    11974 / 11974
    Points
    227,400
    Level
    100

    Re: Confused between 2 terminals of Triac

    I see, I didn't pay attention to this point. It doesn't actually matter with an isolated trigger circuit. Triac is a bidirectional switch, either A1 or A2 can be connected to the input side.


    1 members found this post helpful.

    •   Alt9th December 2016, 16:45

      advertising

        
       

  5. #5
    Full Member level 2
    Points: 986, Level: 7

    Join Date
    Dec 2014
    Posts
    143
    Helped
    3 / 3
    Points
    986
    Level
    7

    Re: Confused between 2 terminals of Triac

    Quote Originally Posted by FvM View Post
    I see, I didn't pay attention to this point. It doesn't actually matter with an isolated trigger circuit. Triac is a bidirectional switch, either A1 or A2 can be connected to the input side.
    Yeah i read the same thing.. But i was learning more about triacs and somewhere i read that the order we choose plays a big role, And that the firing has to come from source connected to terminal 2.
    is there something like that ?



  6. #6
    Super Moderator
    Points: 41,798, Level: 49
    Awards:
    Most Frequent Poster

    Join Date
    Apr 2014
    Posts
    8,549
    Helped
    2061 / 2061
    Points
    41,798
    Level
    49

    Re: Confused between 2 terminals of Triac

    Hi,

    when you read about triac firing you may find the phrase "quadrant".

    With the given circuits you are in quadrant I and III.

    There are triacs that need different drive current in different quadrants.
    And there are triac not able to trigger in all quadrants.

    --> You have to check datasheets individually.

    Klaus



  7. #7
    Full Member level 2
    Points: 986, Level: 7

    Join Date
    Dec 2014
    Posts
    143
    Helped
    3 / 3
    Points
    986
    Level
    7

    Re: Confused between 2 terminals of Triac

    Quote Originally Posted by KlausST View Post
    Hi,

    when you read about triac firing you may find the phrase "quadrant".

    With the given circuits you are in quadrant I and III.

    There are triacs that need different drive current in different quadrants.
    And there are triac not able to trigger in all quadrants.

    --> You have to check datasheets individually.

    Klaus
    i am using a Triac Called BT138-600E.. let me check its datasheet

    - - - Updated - - -

    It says it triggers in all 4 qudarants.. So iam good to go with any of the above circuit ?



    •   Alt9th December 2016, 23:43

      advertising

        
       

  8. #8
    Super Moderator
    Points: 227,400, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    39,187
    Helped
    11974 / 11974
    Points
    227,400
    Level
    100

    Re: Confused between 2 terminals of Triac

    Any triac can trigger in quadrant I and III, G-A1 voltage has same polarity as A2-A1. AC trigger circuits with opto triacs will always work.

    The problem is only for quadrant IV, positive gate voltage and negative A2 voltage, which isn't supported by all triac types.



  9. #9
    Newbie level 4
    Points: 29, Level: 1

    Join Date
    Jan 2017
    Posts
    7
    Helped
    0 / 0
    Points
    29
    Level
    1

    Re: Confused between 2 terminals of Triac

    You can use any on of terminal as incoming and another one as outgoing. Main specialty of TRIAC is bidirectional current flow



--[[ ]]--