Controlling AC light using Arduino with relay

Discussion in 'The Projects Forum' started by Asad ahmed1, Sep 18, 2016.

  1. Asad ahmed1

    Thread Starter Member

    Feb 10, 2016
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    Please tell me the major difference between these two.
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    One of them is ready built and the other one you have to build yourself and needs a 12V supply but they both perform the same function.
     
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  3. Asad ahmed1

    Thread Starter Member

    Feb 10, 2016
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    THANKS FOR YOUR REPLY
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    You can find relays that work at 5 volts, or the same supply as the Arduino uses. That means just one supply for both units. Lower voltage relays need more current than a similar higher voltage unit but not excessively so, the same transistor could run either. The 4.7K resistor is a tad too large; I'd prefer something like 1K there especially for a 5 volt relay. (that is a guesstimate, I would not buy anything until I chose the relay first.)

    Full disclosure: I don't use those boards but as far as I know they run off 5 volts.
     
  5. george4657

    New Member

    Apr 12, 2016
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    The module shown has an optical connection for isolation of the arduino. This is why it does not require a ground connection to the relay module.
    Your sketch would require a connection from the arduino to ground of the transistor and provides no isolation of the arduino.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    The pictorial one has what looks like optocouplers on the PCB.

    The relay on its own should provide adequate isolation - but the opto is a lot more safety margin.

    Can't see anything wrong with the schematic version - but if the ready made PCB makes your MCU go phut, you can blame someone else.
     
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