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Electronics newbie- controlling LED illumination

Discussion in 'LEDs and Optoelectronics' started by salman, Dec 22, 2013.

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  1. salman

    salman

    3
    0
    Dec 22, 2013
    Hello Everyone!

    My knowledge of electronics is very basic so please bare with me. What I am wanting to do is to very precisely control the illumination of a set of LEDs.

    I would like to be able to control the LEDs over a 4 log until range of illumination (ie be able to control the range of brightness from 0-1000) however I would only require access to about 256 steps equally spread out across this range.

    Also I would like the LEDs to be pulsating as they do this.
    How dim can LEDs go before they completely go off?

    The project I am working on is a medical device known as a dark adaptometer for a university project which measures the rate at which a person's eyes adapt to the dark by progressively making a pulsating light dimmer and dimmer.

    Thanks for taking the time to read this. I would really appreciate any advice on what the best way to go about this task cheaply is.
     
  2. kcoer

    kcoer

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    0
    Dec 20, 2013
    Last edited: Dec 22, 2013
  3. salman

    salman

    3
    0
    Dec 22, 2013

    Thanks for you reply :)

    I don't think with the suggestion you've made that I'd have precise enough control of the LED illumination. Would it be possible for me to do something using pulse width modulation?
     
  4. kcoer

    kcoer

    24
    0
    Dec 20, 2013
    Salmon ( i like your name ),

    Use Two potentiometers. Look up 555 timer astable oscillator diagram. For R1 use a pontentiometer and for the resistor leading to your LEDs use a potentiometer. That Pot1 will control the length of the V high. I could be wrong though.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Let me answer some of your questions that have not been answered and ask you for clarification in some places...

    A possible question is how will you set which of these 2656 levels you want? Is it from a microcontroller? Or do you want to dial it up?

    If you are going to dial it up, is a continuous adjustment a problem?

    And when you say precise, do you mean accurate? Do you want to be able to set the same level again (accuracy), or the same level on another LED (precision)?

     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
  7. salman

    salman

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    Dec 22, 2013
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,501
    2,841
    Jan 21, 2010
     
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