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Component values are unknown

Discussion in 'Power Electronics' started by wounder, Jun 22, 2019.

  1. wounder

    wounder

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    Jun 15, 2019
    I have a circuit consisting of ESP8266,STM and a single relay.

    For supplying power to these IC I need an SMPS circuit.

    I got a non-isolated buck converter (using VIPER06Xs) as shown but the component values are unknown.

    Could you please tell the suitable component values needed for this circuit? I chose this converter because the PCB that I will be planning is small in size.

    Voltage needed for ic--

    • ESP = 3.3 V
    • STM = 3.3 V
    • RELAY = 5 V
    https://www.st.com/resource/en/datasheet/viper06.pdf
     

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  2. Bluejets

    Bluejets

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    Oct 5, 2014
    I think you need to supply a bit more info about the project as a whole.
     
  3. wounder

    wounder

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    Jun 15, 2019
    project simply a smart socket.
    figure below gives much details
     

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    Last edited: Jun 22, 2019
  4. Audioguru

    Audioguru

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    Sep 24, 2016
    The circuit posted has its ground connected directly to mains electricity so it presents a serious shock hazard and this thread should be closed with the warning.
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Considering that the SMPS module is non-isolated you are completely right.

    @wounder : I suggest you use an isolated SMPS for safety reasons. The green area then is safe under this condition. You should not trade safety for size!
    upload_2019-6-22_19-9-28.png

    You need to know the current drawn by the relay (5 V is insufficient information). The use this our resource for selecting componnet values.
     
  6. wounder

    wounder

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    Jun 15, 2019
    Could you please provide other SMPS circuit rated(min of output 500mA)
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Use an off the shelf USB charger ...
     
    Martaine2005 likes this.
  8. Martaine2005

    Martaine2005

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    May 12, 2015
    In post #3, how is this circuit connected to ground?. It looks completely fine to me. Am I missing something?.

    Martin
     
  9. davenn

    davenn Moderator

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    Sep 5, 2009

    agreed

    huh ??
    and how did you determine that the off the shelf charger he is using is non-isolated ?

    Yes, his first cct showed a non-isolated converter … BAD
    but the cct in post #3 doesn't and as long as @wounder uses a smps as in post #3 he will be good to go

    I'm about ready to clean up this thread stating with AG's screwball post
    I think AG and Harald have both missed something

    But I await some responses first
     
    Last edited: Jun 24, 2019
  10. Audioguru

    Audioguru

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    The Viper 06 Buck Converter shown in post #1 has its ground connected directly to one side of the electricity with no isolation.
     
  11. davenn

    davenn Moderator

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    Sep 5, 2009

    yes, as I said, that one was bad, but his update in post #3 was good :)
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

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    The op stated that the SMPS is non-isolated...
     
  13. davenn

    davenn Moderator

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    Sep 5, 2009
    that was for the post#1 circuit

    The circuit in post #3 shows a normal, as you state "off the shelf" adaptor
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    My oversight.
     
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