stupid optocoupler question

Discussion in 'The Projects Forum' started by yonubear, Jan 3, 2014.

  1. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    hi amm I am in need of some help I am currently working on a project and this is the first time I have used optocouplers and I am lost.

    If it matters they are PC123 packaged couplers no Idea on the brand.

    just for the sake of making sure they atleast work I tool a AAA battery and a x10 DS10a transmitter ?I wired the DS10a to the collector and emitter and applied power to the coupler and it will trigger the DS10a. however I can't get it to simply turn on an LED or what I am actually trying to do which is trigger an input on a Pi board.

    Thanks,
    Yonu

    P.S. HELP!!!!
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,535
    2,369
    You need to calculate the resistor for the LED and the load res for the transistor emitter or collector.
    Calculated for the supply you are using, in this case AAA cell?
    Any more than the 1.5v you would have destroyed the Opto.
    Look at some of the Manuf. ap sheets for typical applications.
    If you look it up at DigiKey the Sharp app note shows how to configure at fig12.
    Max.
     
    Last edited: Jan 3, 2014
  3. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    Thanks I will have a look at the app note and yeah I know over 1.5 will kill it that was why I was using a AAA for testing.

    yonu
     
  4. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    ok sorry to be back asking agin but I just went through the dip-4 sharp optos and none have a applications note unless I am missing something on the digikey site

    yonu
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,535
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    PDF attached.
    Max.
     
  6. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    thanks that one I have looked at sorry I didn't realize you meant the datasheet however I now feel extremely stupid as I don't see anything about hooking them up
     
  7. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    sorry are you referring to figure 13? if so that makes no sense to me.
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    [​IMG]

    The picture shows a current limiting resistor in series with the input LED and a pullup resistor on the output transistor to allow it to work as an open-collector type output.

    Let's start with this:
    What do you think the output voltage would be when the transistor is turned on (conducting) vs turned off ?
     
  9. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    I don't actually have any idea as I was planning to trigger to ground the GPIO voltage on the PI board is 3.3 so I suppose 3.3
     
  10. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    hey sorry for not posting this a second ago I have it figured it out and I am stupid I had a diagram from a guy on the raspberrypi.org that I had tried and never got to work so I assumed it was me and came to ask for help well I just got to looking at the diagram and the datasheet MaxHeadRoom provided and I had my emitter and collector backwards.

    so yes please some one say it I AM A DUMBASS
    thanks
    yonu
     
  11. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    Hey I am about to order a batch of optocouplers for another project and want some advice what is better 4pin or 6pin?

    Yonu
     
  12. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    The 6 pin is more accessible if you don't already know how you will be using all of them.
    Couldn't hurt to have the extra feature.
    Only if you know that a 4 pin will work for all your applications, buy 4 pin.
     
  13. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    Ok thanks 6 pin it is
     
  14. yonubear

    Thread Starter Member

    Jan 10, 2013
    73
    1
    ok I am back sorry to be a pain I am planning out the circuitboard for my next project and have a stupid question as I really don't understand how they work I need to as a basic switch to short lets say a 2vdc 5ma switch sorry for asking something I am sure is very basic but I normally do this with reed relays but on this circuit I want isolation from the stereo receiver

    thanks,
    yonu
     
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