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

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Rallye

Nov 11, 2015
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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!
 

BobK

Jan 5, 2010
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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
 
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Rallye

Nov 11, 2015
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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


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I originally made this just make a lamp flicker.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
 

Tha fios agaibh

Aug 11, 2014
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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.
 

Rallye

Nov 11, 2015
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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.

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........
 

dorke

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

duke37

Jan 9, 2011
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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.
 

Rallye

Nov 11, 2015
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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.

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.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Can you tell us how old you and your younger brother are?
 

BobK

Jan 5, 2010
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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
 

davenn

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This is sooooo freakin dangerous ... some one is going to get electrocuted !! :( :(

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