How do i use my optocoupler

Discussion in 'General Electronics Chat' started by twn115, Mar 13, 2011.

  1. twn115

    Thread Starter New Member

    Mar 6, 2011

    I am curious...

    I have been experimenting with relays and using them to switch on other circuits, then i came across optocouplers. What i want to know is whether or not i can use these optocouplers the same way as i use my relays? e.g. connect a power source to one side and make the circuit on the other side activate.

    Please let me know.
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    Optocouplers are most often used for electrical isolation of circuits. See the attached schematic for an example. In this case the optocoupler allows a logic level voltage to control a Triac which switches mains voltage.
  3. mkbutan

    AAC Fanatic!

    Sep 30, 2008
    The optocouplers are used in the electronics ckt. where there is two diff. voltages are used in same ckt. eg. 3v and 9v also given eg. by Mr.Tracecom ie. 12v (DC) /117v (AC).
    you will be needing extra ckt. to drive the optocuple it comes in difft. voltage's or you can make it yourself with one LED & Photo Tr. or LDR to get it work properly you have to some R&D
    for that best of luck
  4. k7elp60

    AAC Fanatic!

    Nov 4, 2008
    Welcome to the forum.
    Optocouplers can be used like a relay. It depends on what kind of voltage and current you are switching. As you probably know is the the simple opto coupler consists of IR(infared diode) and a photo transistor. Both the diode and the transistor have specifications. These spec's are really varied and there are hundreds and hundred's of different ones. I have used them for both linear and digital service. In linear service as the input current(diode current) varies the collector(transistor) current varies. In digital switching the input current causes the output transistor to switch on.
    There are high powered ones....namely a solid state relay. In this type a small voltage, usually 3-32 volts can switch many amps of current at different voltage.
    Of course optocouplers come in many different packages also. I have use one that has 4 independant couplers in one package to reverse the polarity of a circuit. That is to say I had a circuit that generated positive going pulses with reference to ground. I make a circuit that made the pulses alternate between negative going pulses if reference to ground to positive going ones.
    I have use dual opto couplers to only switch on a circuit of the two inputs were there.
    There are numerous uses of them.
    orbiter and mkbutan like this.
  5. nipungupta

    New Member

    Apr 21, 2013

    please explain me the cicuit which you have attached.
    do we have to give constant supply at pin no 1 or pin no 4
    of optocoupler moc3021
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
    When Q1 is turned on, it connects ground to the cathode of the LED inside the optocoupler, which lights the LED, which turns on the triac inside the optocoupler, which turns on the external triac.
  7. SgtWookie


    Jul 17, 2007
    Keep in mind that circuits with TRIACs and/or SCRs and/or SSR's (SSR = Solid State Relay) are generally intended for controlling AC circuits only. TRIACs, SCRs and most SSRs will only turn OFF when the current flowing through them nears zero. If you try to use these types of devices with DC, you will need a method other than these devices to stop the current flow, or you'll never get them turned off.
  8. BillB3857

    AAC Fanatic!

    Feb 28, 2009