110v voltage detection

Discussion in 'General Electronics Chat' started by Hessam, Apr 11, 2013.

  1. Hessam

    Thread Starter New Member

    Apr 11, 2013
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    Hey everyone! I'm working on a project that will integrate all my home lighting to a microcontroller. The lights can be controlled manually or digitally from a computer. The only problem I have is that I cannot find a cheap solution for a circuit that will let the microcontroller know if 110v is flowing thru the ac line. Any help would be greatly appreciated.
     
  2. #12

    Expert

    Nov 30, 2010
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    Volts don't flow through the AC line, current does. Please define what you want to detect and how much.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    How about a simple relay.. power the coil with line voltage and use the contacts to pull the micro pin high or low.
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Neon lamp connected to mains shining on a phototransistor connected to μC?
     
    Hessam likes this.
  5. richard.cs

    Member

    Mar 3, 2012
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    Can you clarify if you want to detect either 1) that 110V ac is present - I like the neon lamp idea for this, or 2) that current is flowing - probably best done with a current transformer.
     
  6. Hessam

    Thread Starter New Member

    Apr 11, 2013
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    i would like to detect if there is 110V present. I do like tracecom's idea because i need to make 20 of these
     
  7. #12

    Expert

    Nov 30, 2010
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    NE-2 and a 100 k resistor. No problem. This worked in the 1970's and it will still work.
     
  8. ScottWang

    Moderator

    Aug 23, 2012
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    That is the good idea, we almost using some other parts but expensive and not easy to solve the problem.

    Thanks.
     
  9. richard.cs

    Member

    Mar 3, 2012
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    If you use a photodiode or a phototransistor you will probably see the neon go out during the mains zero crossings. You either need to allow for this with your microcontroller software, or add a small capacitor to filter it out. If you use an LDR they're so slow you won't see it.
     
  10. Hessam

    Thread Starter New Member

    Apr 11, 2013
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    Worked perfectly i appreciate the suggestion!
     
  11. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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