How to control AC powered device using MCU?

Discussion in 'Embedded Systems and Microcontrollers' started by allahjane, Dec 9, 2012.

  1. allahjane

    Thread Starter Member

    Sep 19, 2012
    Hi all,

    Short explanation:

    I give 5v to [power control] --> AC Device ON
    I give 0v to [power control] --> AC Device OFF

    please advice simplest & cheapest option for [power control]

    P.S>I will not use relays

    Long Explanation:

    Basically I want to switch the AC (230V 50Hz) powered device on/off as per the MCU signals (Programmed logic )

    for signalling I have 5v from normal I/O pins

    I have considered Mechanical relays but I don't think they could run on the low current from the I/O pins .. further more I do not want to add a motor driver to control the relay as it will make the design more complicated and much of the power will go for keeping the relays engaged!

    So,I am looking for an electronic device/circuit for the purpose such as a MOSFET or something called as TRIAC

    But, I am pretty dumb at electronics

    can someone recommend a decet way to control the AC power to device using just the 5 v
    Last edited: Dec 9, 2012
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    Nothing says you can't drive the relay with a transistor or MOSFET.

    There are a number ways to do this.

    Solid state, relays, optocoupulers etc.
  3. tubeguy

    Well-Known Member

    Nov 3, 2012
    Look at this:
    The MOC3043 only requires 5ma drive current, drives a suitable Triac very simply.
  4. John P

    AAC Fanatic!

    Oct 14, 2008
    The trouble with triacs is that they inherently involve connecting your low-voltage electronics to the high-voltage line. This really is something to avoid in anything you build yourself, and I believe talking about it violates the terms of service for this board.

    The opto-isolator component is usable, though it still puts the high and low voltages very close together. And that little device isn't good for much current.

    I think you should use a solid-state relay. Much closer to foolproof, can handle plenty of current, can be driven by a microprocessor output pin, don't cost much.

    Pictures of several types here:

    Note that "trouble with triacs" is not the same as "trouble with tribbles".
  5. tubeguy

    Well-Known Member

    Nov 3, 2012
    Thanks for reminding me :).

    Just don't feed them.
    I'm heading to the shop now to work on my rudimentary lathe. :D
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011