incandesent bulbs dimmer

Discussion in 'General Electronics Chat' started by Voltboy, Nov 25, 2007.

  1. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
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    0
    Hello guys.
    I want to do a light system for my bedroom. I want it to have about 3 light states and I don't know if use a PWM to control the dimming or a simple potentiometer. What would be the better?
    And if anyone know how to instead of a switch use a touch plate it would be great.

    Best Regards,
    Yoda
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If it's a bedside lamp, you can get a socket adapter that it touch operated and gives 3 levels of operation. I got mine at an Ace Hardware several years ago. I've never popped it apart to see what the controller is.
     
  3. eeboy

    Active Member

    Sep 27, 2007
    90
    1
    Depends... what LED(s) are you driving? If you truly are lighting your bedroom it may be best to look in the direction of an IC dedicated to controlling LEDs. This would be the most efficient method.
     
  4. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    Eeboy, I'm not using LED's, i know that a LED driver is best for LED's but I'm using incandescent lamps and not for illuminating all the room. Just about 3 small bulbs to give some ambient and to read.
    I think that the best for incandesent bulbs is a potentiometer, so I think maybe I'll use a digital pot.
    About the touch operated mode, I think something of sensing the resistance because when you touch it the resistance increase because of the body (or I'm wrong)
     
  5. eeboy

    Active Member

    Sep 27, 2007
    90
    1
    Not sure where I got LED's from... sorry.

    Are you indicating you are going to use a digital pot to limit the current to the lamps? This is not a good idea. Most digital pots have current limits in the mA range. They are not suitable for this application.

    Take a look at triacs for your dimming control... http://en.wikipedia.org/wiki/Triac .
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Greetings Yoga,

    I'm pretty sure that the digital potentiometers will need some additional circuitry since the pots themselves are fairly low power devices.

    Perhaps you had in mind to incorporate a power MOSFET as the controlling device and use the digital potentiometer in the gate circuit. That should work well.

    hgmjr
     
  7. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
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    But triac's can't reduce current. Or they do?
     
  8. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
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    I like your idea hgmjr. Do you think instead of a MOSFET I could use a power transistor?
     
  9. hgmjr

    Moderator

    Jan 28, 2005
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    My MOSFET suggestion was based on an assumption that the lamps would be powered from a DC source.

    hgmjr
     
  10. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
  11. hgmjr

    Moderator

    Jan 28, 2005
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    A MOSFET transistor and a digital potentiometer could be a useful combination.

    You will most likely need a heatsink depending on the wattage of the lamps you intend to use.

    hgmjr
     
  12. eeboy

    Active Member

    Sep 27, 2007
    90
    1
    I assumed you were using an AC source.

    DC control makes it much simpler. I would use a FET as hgmjr stated and use PWM at the gate to control current. You could substitute a BJT for the FET as well.

    The implementation really depends on what you have available to you.
     
  13. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    Make sure to provide some decent filtering or you'll get a lot of disturbing electrical noise.
     
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