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AC Current Measuring Device

Discussion in 'General Electronics Discussion' started by EngineerWannaBe, Feb 28, 2015.

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  1. EngineerWannaBe


    Feb 28, 2015

    I would like to build a power adapter that measure AC current continuously from a 120Vac 60Hz power source.
    The power adapter will plug to a outlet and an electronic device such as TV or radio is then plug on to the power adapter. It will be a high side current sensing device.

    The goal of the power adapter is to determine when an electronic device that is plugged on it is turned ON or OFF. Say if an electronic uses less than 1mA (peak to peak or rms) during standby or OFF (the adapter saves the threshold current in its memory), the adapter flagged OFF in its output. Otherwise, if more than 1mA, flagged as ON.

    What I am not sure is whether I should measure pk-to-pk or rms. Which will be easier? Is there any microprocessor that can use to achieve this? Any idea on what are will be the major components?


  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    You don't need to measure current to do this, just detect a current.

    The easiest way is to have three or four pairs of diodes in inverse parallel placed in series in line with the active (hot) lead. This voltage drop can be used to drive an optocoupler with the isolated output of the opto used to interface to your circuit.

    Careful design of this will allow you to detect different levels of input current if you allow the output to operate in the linear region.
    BobK likes this.
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