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Looking for Templates for an Analog Circuit to Control LEDs from a Photo Diode

Discussion in 'General Electronics Discussion' started by Gebhard Sengmüller, Nov 24, 2017.

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  1. Gebhard Sengmüller

    Gebhard Sengmüller

    4
    0
    Nov 24, 2017
    Hello everyone on the forum,

    I am trying to build an electronic circuit that can drive a bright array (size appr. 40 by 60 mm) of white LEDs from a photo diode. By that I mean that the LED array should be able to change its brightness according to the brightness induced to the photo diode. This should work with a maximum frequency of 2 MHz. The circuit should also include a potentiometer to gamma correct the signal.

    I need this for a mechanical television system I am building, as described here: http://gebseng.com/11_big_paul/big_paul_brochure.pdf


    Since this system (the spinning Nipkow Disk) blocks out 99.99 percent (sic!) of the available light, the photodiode needs to be very light sensitive, and the LED array needs to be very bright.

    As you can probably tell from this writeup, I am not an electronic engineer myself, but I have decent soldering skills and a basic understanding of analog electronic parts.

    If you could suggest a tutorial, or even better existing examples for similar circuits that I could modify for my purpose, this would be very helpful. I am not sure what the right terms for this kind of circuit are, but I guess it can't be too exotic.

    best,

    geb

     
    Last edited by a moderator: Nov 25, 2017
  2. AnalogKid

    AnalogKid

    2,571
    739
    Jun 10, 2015
    What are the voltage and current requirements for the LEDs?

    ak
     
  3. Gebhard Sengmüller

    Gebhard Sengmüller

    4
    0
    Nov 24, 2017
    Thanks for your reply!

    I don't really have voltage and current requirements so far. I need to build an array of LEDs that covers 40 by 60 mm, and they have to be as bright as possible, since only 0.01 percent of the light will pass through (due to the very small holes in a very fast rotating disk)

    geb
     
  4. Gebhard Sengmüller

    Gebhard Sengmüller

    4
    0
    Nov 24, 2017
    About the LED type: I am not sure if I can pick LEDs designed for lighting purposes. Are they dimmable like smaller LEDs, and can they be modulated at up to 2 MHz?

    If yes, how about this one:
    https://uk.rs-online.com/web/p/visible-leds/8792889/

    I would arrange 54 of those in a 6 x 9 grid.

    Specifications:
    LED Colours White
    Mounting Type Surface Mount
    Number of LEDs 1
    Forward Voltage 38 V
    Luminous Intensity 461.5 → 547.5 cd
    Number of Pins 2
    Viewing Angle 120 °
    Luminous Flux 1400 → 1800 lm
    Lens Shape Square
    Dimensions 7 x 7 x 0.7mm
    Series DURIS S10
    Colour Temperature 5700K
    Lens Colour Yellow
    Forward Current 20 → 400mA
    Lens Finish Diffused
     
  5. Gebhard Sengmüller

    Gebhard Sengmüller

    4
    0
    Nov 24, 2017
    OK sorry, I guess this would be a total of 810 W, which is probably too much ;)
     
  6. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    800 Watts in a 4x6 cm square? No problem, All you need is water cooling and a car radiator (with fan.)

    Bob
     
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