Help with variable input to PS2501-4

Discussion in 'The Projects Forum' started by mark_anderson_us, Oct 3, 2013.

  1. mark_anderson_us

    Thread Starter New Member

    Oct 3, 2013
    Hi All

    I'm pretty new to electronics. I'm building a circuit where I need to sense a DC signal between 9 and 24v DC and an output to a microcontroller. I want to use a PS2501-4, but I'm kind of stuck on figuring out the range of input voltages it supports and what I should use to ensure this range of voltages will trigger it.

    I looked at the data sheet, but can't for the life of me figure out what the max input voltage is.

    In addition to this, I then need to figure out how to generate enough forward (for the 9-24v input) to trigger the device. I'd like to keep the no of components to a minimum due to size limitations.

    Any help/explanations would be appreciated


  2. #12


    Nov 30, 2010
    It's a 10 ma opto. You need to use a resistor to convert 24 volts (-1.14Vf) into 10 ma.
    That's a least 2286 ohms. Start with a 2.7K resistor in series with the input signal to the LED inside the coupler. That will allow 2.9 ma at 9 volts input and 8.47 ma at 24 volts input. Now the input is safe.

    This chip has an 80% guaranteed transfer ratio so you can bet on the output transistor passing 2.3 ma to ground. Whatever voltage you are switching on and off, use a resistor to limit the current to V/.0023 or less. That will give you V for an output when there is no input voltage and less than .2 volts when there is any input voltage from 9V to 24V.
    Last edited: Oct 3, 2013
  3. mark_anderson_us

    Thread Starter New Member

    Oct 3, 2013
    Thanks #12! Will give it a shot.