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
    20
    1
    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:
    https://electrosome.com/transformerless-low-cost-power-supply/
    http://www.electroschematics.com/5678/capacitor-power-supply/

    My Schematic:
    230V_extension.png

    BOM List:
    230V_BOM.PNG

    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
    963
    232
    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.

    Ron
     
  3. tudstudent

    Thread Starter Member

    Jun 6, 2009
    20
    1
    He Ron,

    Never heard of, so did a quick google and came accross this great explanation:
    http://www.renesas.eu/products/opto/technology/ac/index.jsp

    So broadend my search for a good circuit (why develope something new if it already exists):
    http://electronics.stackexchange.com/a/33428

    The only question open here is:
    If you have the 50Hz 230VAC the opto will show light bulbs like figure 3 on this link:
    http://www.renesas.eu/products/opto/technology/ac/index.jsp
    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
    4,995
    745
    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
    20
    1
    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

    Moderator

    Mar 24, 2008
    20,766
    2,536
    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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