Detecting AC voltage (contactless)

Discussion in 'General Electronics Chat' started by Kenjutsu, Feb 24, 2015.

  1. Kenjutsu

    Thread Starter New Member

    Jul 26, 2010
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    Hello everyone,

    I want to build a circuit that can signal an Arduino that an AC voltage is present in a cable or not. I am not interested in measuring the AC volt/current. Since I have no experience working with AC circuits, I would prefer a contactless solution.

    I am clueless on how to proceed :oops:
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    What is the AC voltage?
    120/240V?
    50/60 Hz?
     
  3. Dodgydave

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    Jun 22, 2012
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    Last edited: Feb 24, 2015
  4. Kenjutsu

    Thread Starter New Member

    Jul 26, 2010
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    230V 50Hz
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Here is the safe way of doing it:

    Get an old 4Vdc to 5Vdc (no higher) cell-phone charger that looks like this:

    [​IMG]
    Cut off the output plug, and wire it to a load resistor, like 470Ω or 1KΩ. Check the output voltage across the resistor with a DC Voltmeter. If 5Vdc or less, wire the 0V output end of the resistor to the Arduino Vss (Gnd), and wire the +5V output end to an Arduino Port pin.
     
  6. Dodgydave

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    Jun 22, 2012
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    see circuit in post #3, contactless detection
     
  7. MikeML

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    Won't work if no current is flowing in the sensed circuit.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Do you need contact-less voltage detection even in the absence of current?
    Max.
     
  9. Dodgydave

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  10. Kenjutsu

    Thread Starter New Member

    Jul 26, 2010
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    Thank you for all the replies. Like I said, I have never worked with AC powered circuits before. Basically what I want to know is: is there AC power in the cable, yes or no.
     
  11. MaxHeadRoom

    Expert

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    Here is one from another site.
    [​IMG]
    Max.
     
    cmartinez likes this.
  12. MikeML

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    Good reason to use the cell-phone charger...
     
  13. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    What kind of cable are you working with?

    Ken
     
  14. Kenjutsu

    Thread Starter New Member

    Jul 26, 2010
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    It is a standard "household" cable that is rated at 20A. I think just to clarify further: I want to monitor several mains appliances/devices to see of they are still receiving AC power from the grid.

    Something like: TV power ON; Fridge power ON; Fan power OFF; and so on. The idea is to determine whether there is a general power failure (blackout) or just one circuit breaker tripped.
     
  15. Dodgydave

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  16. Kenjutsu

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    Jul 26, 2010
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    This looks interesting. I'm sure I'll be able to open it up and hack to provide input to the Arduino. At that price point, it is probably cheaper than a DIY solution as well. ;)
     
  17. MaxHeadRoom

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    In many cases these electricians neon type testers require that the unit be held by the operator for them to operate via earth leakage, the return path is a very minute current through the body.
    Max.
     
  18. alfacliff

    Well-Known Member

    Dec 13, 2013
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    I have at home a stud finder with wireing detector. it is for findi9ng studs in walls and live circuits in walls. it uses a coil like the previous diagram (numbedr 11) and works by induction. even a circuit drawing no current will show its there. ou might try a small ausio transformer, remove the Bridge from it and the open end of the E shaped core should pick up ac induction.
     
  19. Kenjutsu

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    Jul 26, 2010
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