Led dimming circuit (pwm)

Discussion in 'General Electronics Chat' started by majkl7777777, Sep 19, 2009.

  1. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
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    Sorry, I found some projects with PWM, I tried most of them, and without any luck :(

    Can someone who tried that post me a schematic?

    Or if someone would be so nice paint a layout on prototype board? please...

    can be variable frequency, or constant (houndreds of Hz)

    Duty cycle range 1% - 99% or something like that...

    Best would be to use 555 Timer

    want to make it for high power LED(s) some Watts.

    Thanks for an advice :)
     
  2. mauro.laurenti

    Active Member

    May 8, 2009
    68
    0
    well,

    a PWM schematic using the 555 can be found on www.ti.com datasheet.
    With the 555 you can not really achieve the PWM range you have asked for...

    by the way if nothing you have tried work, it could be also due to some mistakes you have done.

    Probably if you post the schema you have used, people can better see where the problem is...

    Ciao,

    Mauro
     
  3. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
    10
    0
    hi,

    I have tried this:

    http://www.reuk.co.uk/LED-Dimmer-Circuit.htm

    but if you or somebody else has a schema with some other IC and could be used for my purpose I would be very greatful :)

    In short,

    I want to dim a high power LED or some high power LEDs with a trimer lineary without any flicker effect. Dont know what frequeny must it be to dont notice being the LED turned on/off.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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  5. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
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    try without any result...

    is there someone who did the PWM and want to send me a photo or paint of prototype board... :(

    please :(
     
  6. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
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  7. Wendy

    Moderator

    Mar 24, 2008
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    You did notice the picture of the prototype board in the link I gave you?
     
  8. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
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    Yes I did :) thanks a lot Bill...

    I have another question... Can be this schema, or Bill's modified, or added by something to do this:

    there should be a button to do the following:

    1. Press : Turn on by fading in the LED to the intensity setted up by potenciometer...
    2. Press : Delayed by few seconds, and than fading out till switching off

    thanks for advices :)
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    It could be done, but there would be some designing involved. You would be better starting from the other PWM circuit I showed that translated voltage into PWM, then you could have a capacitor charge and discharge.

    I don't see the first design lending itself to that very well.
     
  10. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
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    Which schema should be best? Could you send me a direct link for the purpose I describe you Bill please?
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Thing is, you want a custom design. I've done this, but right now is not a good time. Here is the schematic I was talking about.

    [​IMG]

    The PWM range is between 1/3 and 2/3 the power supply voltage. If you were to connect a capacitor and a large resistor (1MΩ) on the plus input, which a switch between them and the PWM control pot.
     
  12. majkl7777777

    Thread Starter New Member

    Sep 18, 2009
    10
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    Sorry Bill, but I dont understand you... For what is not a good time? And I dont get the schematic eighter... Square wave out = my output for the LED. Right?

    For what is the PWM out?and the R1... Should it not have three pins?

    sorry, but I really dont get it :(
     
  13. Wendy

    Moderator

    Mar 24, 2008
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    Means I have a full plate, lots of other irons in the fire, I work for a living. :D

    OK, here is what I was talking about. You'll have to tweak the components to whatever you need.

    [​IMG]
     
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