230 detection - circuit question

Discussion in 'The Projects Forum' started by tudstudent, Mar 22, 2015.

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  1. tudstudent

    Thread Starter Member

    Jun 6, 2009
    HI all,

    I am currently busy with creating an extension for a to be defined interface (arduino, RPI, atmega...).
    Initially I just focused on RPI so I wanted to use GPIO, but since at the moment my breakout will use a lot of them an alternative communications method might be better (rs485).

    So in short at the moment I am focusing on detecting a light switch turning ON/OFF. At the beginning I used a transformer based power transformer to go to 5V. However I did not like it to have a bulky transformer on my print so I looked further. Since I am on 50Hz 203VAC I needed to have something which was able to phase correct and "stabilize".

    I found the following 2 links and created based on those the circuit attached:

    My Schematic:

    BOM List:

    The 2 main questions I have are:
    1. Does this work for my purpose (no delay "off" because of the capacitor, OFF will immediately shut the optoled)
    2. Are the parts I selected correct.

    Thank you in advance.
  2. Reloadron

    Active Member

    Jan 15, 2015
    Why not just use a simple AC type opto coupler. You want to detect the presence of 230 VAC On/Off correct? I would just use a selected opto coupler since you don't want to go the transformer route.

  3. tudstudent

    Thread Starter Member

    Jun 6, 2009
    He Ron,

    Never heard of, so did a quick google and came accross this great explanation:

    So broadend my search for a good circuit (why develope something new if it already exists):

    The only question open here is:
    If you have the 50Hz 230VAC the opto will show light bulbs like figure 3 on this link:
    They advise to use a C. Do I need somthing in parallel to R3 (or another place and if so what type/value would you advise).
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    I would strongly recommend using a transformer to feed your detection circuit,as opposed to a Live circuit on the mains...

    then feed it into your opto.
  5. tudstudent

    Thread Starter Member

    Jun 6, 2009
    Could you please elaborate a little more on that?
    I am no expert in this area and I have thought of a lot of different solutions. My current solution was based on a transformer...
  6. Wendy


    Mar 24, 2008
    Please take the time to read our terms of service. Transformerless power circuits are not allowed here.

    Terms and Rules

    Use and isolation transformer and start a new thread.
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