+ Post New Thread
Page 2 of 2 FirstFirst 1 2
Results 21 to 27 of 27
  1. #21
    Super Moderator
    Points: 76,326, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,478
    Helped
    3521 / 3521
    Points
    76,326
    Level
    67

    Re: Multiple relay with controllers

    Hi,

    Is this circuit is correct..?
    It does not work ... how can it be correct?

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



    •   AltAdvertisement

        
       

  2. #22
    Super Moderator
    Points: 80,586, Level: 69
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    13,205
    Helped
    4410 / 4410
    Points
    80,586
    Level
    69

    Re: Multiple relay with controllers

    With R4, R9 and R13 replaced with a link it should work. As the schematic showed it, might have worked but the highest voltage you could get on U1 inputs would be half VCC (because of the voltage divider, example R4 and R1) less some extra voltage dropped by the transistor in the PC817. That might not be enough to ensure logic levels were satisfied. Personally, I would link out R4, R9 and R13 and also increase the value of R1, R2 and R10 to say 4.7K as there is no advantage in the extra current being drawn through them.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



  3. #23
    Super Moderator
    Points: 76,326, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,478
    Helped
    3521 / 3521
    Points
    76,326
    Level
    67

    Re: Multiple relay with controllers

    Hi,

    ...or use a HCT595...

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



    •   AltAdvertisement

        
       

  4. #24
    Super Moderator
    Points: 258,547, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    45,137
    Helped
    13723 / 13723
    Points
    258,547
    Level
    100

    Re: Multiple relay with controllers

    For correct shift register operation, the clock signal has to to fulfill the maximum rise/fall time requirements of HC logic family. A standard opto coupler probably can't guarantee this, high load resistance values further slows down the edges. An ST clock buffer may be required.

    - - - Updated - - -

    ...or use a HCT595...
    To save the useless series resistors?



  5. #25
    Super Moderator
    Points: 76,326, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,478
    Helped
    3521 / 3521
    Points
    76,326
    Level
    67

    Re: Multiple relay with controllers

    Hi,

    To save the useless series resistors?
    No, just to minimize the count of modifications to the given schematic...

    There are so many ways and so many reliable and proven circuits available ... the OP could use.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  6. #26
    Full Member level 5
    Points: 1,963, Level: 10

    Join Date
    Sep 2016
    Posts
    313
    Helped
    1 / 1
    Points
    1,963
    Level
    10

    Re: Multiple relay with controllers

    Quote Originally Posted by venkates2218 View Post
    Attachment 153567

    Now it is correct..?
    Does series resistor is required between the PIC and shift register pins..?
    Is it ok to place an resistor of 470R in LATCH,CLOCK,SERIAL DATA path to the controller..?



    •   AltAdvertisement

        
       

  7. #27
    Super Moderator
    Points: 76,326, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,478
    Helped
    3521 / 3521
    Points
    76,326
    Level
    67

    Re: Multiple relay with controllers

    Hi,

    Are you aware that you didn't show the 470 resistor in your schematic?

    Generally you are free to use as many resistors you like.
    The only thing you have take care is to satisfy the datasheet specifications.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



--[[ ]]--