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EMF Sensing

Discussion in 'General Electronics Discussion' started by Jfrank9900, Oct 24, 2013.

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  1. Jfrank9900


    Oct 24, 2013
    I am looking for help. I have, for awhile now, been looking for a small viable solution to have an emf sensor. Electromagnetic Field Sensor. I have been using a emf (Ghost meter) for measuring it currently to log the data using voltage from that device into an arduino board. I have lately been experimenting with telephone pickups, they seem to be able to pickup the emf for audio use. Is there anyway to convert this frequency that I am hearing from the telephone pickup and to a voltage signal that I can read in the arduino??
  2. BobK


    Jan 5, 2010
    The frequency you are hearing is likely 50 or 60 Hz, depending on where you live.

  3. Jfrank9900


    Oct 24, 2013
    I am assuming that the frequency is changing and that is what I am looking for. When I get it closer to the breaker panel it gets louder and louder. Not sure if this is true. Meaning the emf is getting greater and greater. I would like to try to get the response that I am getting from the pickup in a voltage form to record it.
  4. BobK


    Jan 5, 2010
    Oh my god, your breaker panel is infested with ghosts!

  5. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    A bit early, isn't it? Halloween is in a week.

    You can't hear electromagnetic fields. I'm not sure what you'r problem is. Can you try to elaborate a bit more to help us understand what you want to achieve?
  6. shrtrnd


    Jan 15, 2010
    I get it. He's got a ghost hunter EMF meter. It makes a noise when it's near a voltage
    source. His issue is that he's wondering why, as he gets it closer to a voltage source,
    the meter makes a louder noise.
    I'm checking my manual on Mr. Spock's tricorder right now, to diagnose the issue.
  7. CallumA


    Jul 22, 2013
    It's been 3 days, hope I'm not too late. I think the question was "I have an EMF detector which makes a sound (increasing in volume or frequency?) and I want the output to be read to the Arduino". At least that's how I'm going to interpret it for this answer...

    This should be relatively simple really. If you're dead set on using the device you have and it outputs a louder volume closer to a "ghost" (or, more likely, electronic equipment) you should test the speaker output with a multimeter with it outputting as loud as possible. If the voltage is under 5V it should be fine to connect directly to the analogue input on the Arduino (I'm assuming this is a small battery-powered device) but equally the maximum should be somewhere >= 2V to get a nice precise range. If the maximum is 1.1V or less it would be possible to use the Arduino's built in voltage reference for more precise analogue measurements in that range.

    If it outputs a higher frequency the more EMF is detected that's a bit more complex but it still really a matter of software, Google "Arduino frequency measurement" or something. I can probably help explain if you need help with that but there's a library you can use somewhere.

    If you want to create something yourself it would be much simpler to just use the analogue input on the Arduino to directly detect EMF. Make have an article on this:
    You can also Google "Arduino EMF detector" for masses of results.

    Basically what they did was get a piece of wire to use as a probe and connected it to the analogue input on the Arduino then used a 3.3MΩ resistor pulldown to ground (you can use more resistance to increase sensitivity (probably), I think I've done a similar thing with no resistor in the past which did work and gave me an analogue value down to around 300 or something and up to 900 or so). That can be read in Arduino with analogread and will give you a value which should increase as you get closer to a source of EMF (try putting it near a transformer like a phone charger). They have an Arduino code download on that page.

    Hope that helps.
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