removing 120 hz from ac line

Discussion in 'Off-Topic Members Lounge' started by stevensrd1, Oct 7, 2011.

  1. stevensrd1

    stevensrd1

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    I have a meter that can read hz. I took my 12v 1 watt solar panel and connected it to the meter set to read in hz. I found anywhere light from ceiling light shines on my solar panel I get a reading of 120hz. I tried a full spectrum fluorescent bulb but it also puts out 120 hz. I bought a corn led light thinking maybe leds would do different,,same result. I found using regular leds on batteries gives no hz reading, except for the red green blue color changing leds. Also a 12 volt light used on a 12 volt battery gives no hz reading. But I want to use the ac light socket, so how do I remove the 120 hz? Thanks...
    stevensrd1, Oct 7, 2011
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  2. stevensrd1

    duke37 VIP Member

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    I presume that you have AC mains at a frequency of 60Hz. This has a voltage peak 120 times/second and fast acting lights will give flashes at this frequency and I do not see how these can be removed.

    Small flourescent lights rectify the mains, smooth it slightly, and chop it up at high frequency, these may give less 120Hz output but may have a large much higher frequency component.

    You could use a stabilised power supply driving filament lamps or leds if you wish to use the mains.

    Duke
    duke37, Oct 7, 2011
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  3. stevensrd1

    Resqueline Moderator

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    Old fluorescent lights use simple inductor ballasts and will thus "flash" with twice the mains frequency. It's no surprise most (cheap) mains LED's "flash" like that too.
    Modern fluorescent ceiling ballasts are electronic and will produce a steady light. They're better for both your eyes and the tubes.
    Fluorescent bulbs are electronic but have only a small smoothing capacitor so I guess they still "flash" slightly.
    Notice that you can set the meter to AC and see the level of this "flashing", not only detect the presence.
    Why is this important for you?
    Resqueline, Oct 7, 2011
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  4. stevensrd1

    daddles VIP Member

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    If you really need to remove the 120 Hz part of the signal, one way to do it is to create a 120 Hz notch filter. This will take a bit of design and probably some active circuitry. Look up "120 Hz notch filter" for more details -- or you can buy a ready-made unit (but it probably won't be cheap).
    daddles, Oct 7, 2011
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  5. stevensrd1

    TBennettcc VIP Member

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    ...or just rectify it with a diode bridge and some smoothing capacitors? Can you use DC?

    If I read that correctly, you're looking to smooth out the output from the solar panel when the solar panel is lit by a household current AC light?
    TBennettcc, Oct 8, 2011
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