Would this SSR with 3-32V control signal need a current limiting resistor?

Discussion in 'The Projects Forum' started by kender, Jan 12, 2014.

  1. kender

    Thread Starter Senior Member

    Jan 17, 2007

    There are lots of SSRs, which switch AC and use 3-32V DC as a control signal. I'd like to use one of them and control it with a 12V signal. I haven't worked with large 3-32V SSRs, however I've worked with small IC-size SSRs. I'm trying to figure out if the control side of the SSR already has a current limiting resistor, or I need to add one. The specs for the input are here: datasheet page 4.

    The datasheet doesn't give the forward voltage of the LED inside the relay, no min or typical current. To me, this implies that relay just accepts the control voltage it's rated for and takes care of current limiting internally.

    I've also found this thread on the Arduino forum, which says that a 3-32V relay should have internal current limiting resistor.

    Folks, what do you think?

    - Nick
  2. MaxHeadRoom


    Jul 18, 2013
    As long as your supply is within the input voltage range you do not need a series resistor.
    The limiting is internal.