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    Capacitive voltage dropper for LED pilot lights -- test

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    RODALCO2012

    by RODALCO2012

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    This test was done for Electrotech Forum where a LED circuit with capacitive voltage dropper was discussed.

    It shows the importance of having correctly rated mains Capacitors (X2 rated) or at least twice the peak rating of the mains voltage (1 kV in this case)

    Mains Voltage used was 240 Volts 50 Hz

    Initially three LED's were subjected to a test.

    LED-1 was connected to four 47nF 1kV rated caps ( in parrallel ) 188nF
    LED-2 was connected to a 0.1uF 300V rms rated capacitor
    LED-3 was connected via a resistive voltage divider consisting of two 27 k.ohm 1 Watt resistors.
    All LED's have a 1N4448 blocking diode in parrallel with the led.
    Also a current limit R of 680 ohm or 1 k.ohm ( 1 W ) was used to reduce inrush current destroying the led.
    Parrallel cap discharge R's were fitted too 270 k.ohm or higher.

    Before I had my camera ready the first Cap had exploded at 92 events. I did not expect that cap to fail so early in the test.

    LED-2 was replaced with similar LED and same type capacitor. That one failed within about 200 minutes, the cap shorted internally and remained intact but the series R burnt out, LED and diode failed.

    LED-4 was added later with a X2 rated 275 V rms cap of 0.1 uF. that worked fine.

    Current measurements are shown of the circuits in use.

    The timing intervals were 57 seconds on 3 seconds off every minute.

    The survey was done over 17000 events

    I created this video with the YouTube Video Editor (http://www.youtube.com/editor)