Electronic 220/12 v switch.Pwr can not be rectified!!??

Discussion in 'General Electronics Chat' started by foundit, Feb 7, 2012.

  1. foundit

    Thread Starter New Member

    Mar 9, 2008
    hi everybody, please tel me why I can not get a dc from an electronic step down adapter (that is used to light a halogen spot 50W).

    I used a bridge and a cap. but I got 0.4 volt dc why, should i use a fast diods instead??

    thanks for help
  2. RiJoRI

    Well-Known Member

    Aug 15, 2007
    Posting a schematic will help people here aid you.

  3. foundit

    Thread Starter New Member

    Mar 9, 2008
    thank you for the rpely,

    I'm late, the first time I used a digital multimeter that gave a false result, when I tried again and pluged an oscilloscope I found 10Khz very narow spikes that vary in amplitude by the 50Hz line frequency, so I used the same bridge and the same cap. but I tested it with an analogue multim. and get around 17 V (open circuit). a block of leds then connected to the rectified current without current limiting R, the leds illumnited with flickering intense light, using R, the flickers decreased but not disapeared Why, should I connect a small cap (0.1 to 1 uf) parallel to the electrolytic one? I wish I will have time to try again.

    I have no schematic, but it is a very simple circuit of a rectifier bridge and a filtring capacitor to feed a led block and maybe to charge a lead accum.

    I've got some photo of the oscilo. screen, but they are of low quality, may I have time to post it.

    Thank you forums.:rolleyes:
  4. K7GUH


    Jan 28, 2011
    When someone on AAC asks you for a schematic, it is perfectly OK to draw one by hand. Especially if it is simple. As we used to say in the olden days, one picture is worth ....