Proper use of Open-Drain Output pins

Discussion in 'General Electronics Chat' started by Marquis, Sep 5, 2016.

  1. Marquis

    Thread Starter New Member

    Jan 18, 2015
    I'm a little confused about open-drain outputs. In my case I have a microprocessor that will be running on a battery so I'm trying to save power. I have a few components, a sensor and a large draw light that draw a fair bit of power. I want to use the pin to turn power to them on and off. How do I go about that using the open-drain pin?

    I'm more used to working with arduinos where I can just turn off the pin to disable the component and save power. How do I go about the same thing using an open-drain pin?

  2. ericgibbs

    Senior Member

    Jan 29, 2010
    hi M,
    Which type of MCU is it.??
  3. Papabravo


    Feb 24, 2006
    Using an external pullup with an open-drain output only consumes power when the output is LOW. When you turn the output off, it goes to the value of the voltage on the other side of the pullup resistor and no current flows.
  4. Marquis

    Thread Starter New Member

    Jan 18, 2015
    I am using an arduino for some of it, but to extend things I'm using the Maxim DS2408. It's a 1-wire switch that turn on and off some of the other items.
  5. Marquis

    Thread Starter New Member

    Jan 18, 2015
    I should also add that some of the things I want to control will likely draw more current than the chip can sink. So I take it I need to use it control a larger transistor.
  6. hp1729

    Well-Known Member

    Nov 23, 2015
    What are you having trouble with? Did you do the "Blink the LED" exercise on the Arduino? when the output goes low the output turns on. Turn on a PNP transistor to drive something of higher power.