Dimmer soft start

Discussion in 'The Projects Forum' started by stpx, May 17, 2011.

  1. stpx

    Thread Starter New Member

    Dec 31, 2010
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    0
    Hello

    Can a standard house lamp dimmer be used as a manual method to charge filter capacitors in an AC to DC power supply (~120 VAC to 170 VDC).

    A thermistor is in series with filter capacitors but for testing I would like to test it slowly by increasing voltage in steps. Any ideas are greatly appreciated.

    I already tested it up to 25 VDC by using a DC power supply.

    Thanks
     
  2. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    My first idea is that "direct from the power line" is forbidden on this site.
     
  3. stpx

    Thread Starter New Member

    Dec 31, 2010
    7
    0
    Currently I don't have a dimmer as in a wall socket. I was planning to buy one and install it after the isolation transformer if that is your concern.
     
  4. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    Cool. I just got suckered into the forbidden zone yesterday because I didn't recognize the name of a perpetual motion scam. Didn't want to tick off the Powers That Be.

    so...yes. A standard dimmer can be used to power a rectifier to charge capacitors, as long as the rectifier has enough reverse voltage ability and such as that. They do tend to have a dead zone at the beginning where nothing happens as you start turning the knob, then "blink" you have 30 volts DC. Be careful about that, and be careful about getting shocked. It hurts the same, even after an isolation transformer.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I have used them for heater circuits. They are rather wimpy though, so be careful.
     
  6. stpx

    Thread Starter New Member

    Dec 31, 2010
    7
    0
    Thank you for your concern about my safety, I'll be under supervision in my university while attempting this.
    I just don't want to test the circuit right away using intended full voltage.

    I did several tests using function generator and DC power supplies, everything seems to work as designed, most importantly the bleeder resistor and inrush current limit thermistor. all components are rated for at least double the target working voltage and currents.
     
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