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What resistors should I use to reduce power from 120v outlet

Discussion in 'General Electronics Discussion' started by Rallye, Nov 11, 2015.

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  1. Rallye

    Rallye

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    Nov 11, 2015
    Hello, I am new to this forum and need help with a project I am working on with my younger brother.


    Using Arduino Uno broad and Seeed relay shield to turn the power on and off via the computer. Have the power coming straight from the outlet but the resistors I got from Radio Shack cant handle that and start to get hot really quickly because they were only 100ohm 10watts. (small white ones) and some of the tape around it started to melt!!!

    What kind of resistors do I need? (I have yet to determine how many ohms the output has to be but can buy a few and test the ones I need)

    Any help would be appreciated.


    Thanks!
     
  2. BobK

    BobK

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    Jan 5, 2010
    Stop! Now! Drop those resistors and walk away!

    You cannot use resistors to reduce line voltage for electronics. What you are doing is dangerous, could kill you or someone else.


    If you want to power an Arduino, you need to use a low voltage power supply. Cell phone chargers are cheap and put out a very accurate 5V. Use one of these.

    Bob
     
    Last edited by a moderator: Nov 12, 2015
    Ian, Martaine2005, KJ6EAD and 2 others like this.
  3. Rallye

    Rallye

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    Nov 11, 2015

    I dont want to power the aurdino, I want to send power in to something using a relay switch which turns it off right away.

    I originally made this just make a lamp flicker. Now I want to put something else on the other end instead of lamp but need to reduce the power. How can I do that?

    Thanks for the response BTW
     
  4. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    You probably want to looking into driving a triac. A triac is like a relay but can be switched much faster. It is the heart of a common dimmer used in household circuits.

    Need more details of what "something else" is.
     
  5. Rallye

    Rallye

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    Nov 11, 2015
    is there anyway just reduce the power without changing what I already have? because what I made so far got the job done, just the resistors started to heat up........
     
  6. dorke

    dorke

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    Jun 20, 2015
    Please a clear explanation would help.
    Can you put a diagram of what you did and why?
     
  7. duke37

    duke37

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    Jan 9, 2011
    Have you still got a younger brother? Do not teach vulnerable people dangerous practices.

    Get a power supply (wall wart) which gives the voltage you require without the danger of playing with the mains.
     
  8. Rallye

    Rallye

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    Nov 11, 2015
    yeah when i noticed what he was doing it didnt seem right to me, thats why i stopped him and started to research myself lol

    I didn't think of using a wall wart.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Can you tell us how old you and your younger brother are?
     
  10. Rallye

    Rallye

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    Nov 11, 2015
    17 and I am 23.
     
  11. BobK

    BobK

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    Jan 5, 2010
    You really need to tell us what you are powering, what are its voltage and current specifications. Resistors are rarely the best way to reduce power.

    Bob
     
  12. davenn

    davenn Moderator

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    Sep 5, 2009
    This is sooooo freakin dangerous ... some one is going to get electrocuted !! :( :(

    thread closed
     
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