3.2V DC to control 24 volt 0.75 A. AC device.

Discussion in 'Analog & Mixed-Signal Design' started by Odin212, Oct 15, 2016.

  1. Odin212

    Thread Starter New Member

    Oct 15, 2016
    so i want the 3.2 volts coming off of my control device to control a 24 volt 0.75 amp actuator. When the control device is high i want the power to be delivered to the actuator and i want no power to be delivered to the device when the control unit is not outputting voltage. I have been cruising the internet to find out the best way to do this and so far the answer i have arrived at is a opto isolator triac circuit.
    this is just a generic circuit i found online. I did not make it. I get what u1 does and from what i can tell u2 is there to reduce the current going through u1 but while i kind of understand how it works i cant figure out what components to use for my application. I looked up the MOC3041M and it seems ok but i just get lost the minute i hit digikey and there are 100,000 different ones. For U2 i have literally no idea which one to get...
    Is there an easier way to do this?
    If not what parts should i use?
  2. #12


    Nov 30, 2010
    That's a very commonly known circuit. The triac in U1 is only a momentary conductor, a few milliseconds, used to fire U2.
    This output side only works for an AC circuit. You never said your 24 volts was AC. Is it?
    If it is, you need a triac rated for comfortably more voltage than 24 VAC and 0.75 amps.
    Something like 120 VAC and 3 amps to 5 amps (if this isn't going into a production line machine).
    These are so common you might find 10,000 of them that will work.
    Oh...wait...you did.:D

    Sort the candidates by price.
    U1 is a zero-crossing opto-isolator.
    Pick a cheap U2 that fires in quadrants I and III
    The only problem you have is being overwhelmed by options because this is so common, so easy, and so cheap to do.