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  • neo1786

    neo1786

    MemberOct 24, 2008

    Rolling LED display

    Hey guys
    Hav to make a rolling LED display.can u plz tell me how to go about it.
    i hav to mount around 500 leds on a PCB of 1 square feet.i hav learnt how to drive the LED's but want to know how to interface so many LEDS with the microprocessor..................plz help,all suggestions welcome
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  • reachrkata

    MemberOct 27, 2008

    Can it be done this way? Others may please correct me if wrong.

    Commonly used LCD drivers take in data serially to control the array of segments/pixels of an LCD. If you run the LCD driver in 1/2 Bias mode, I am sure you can use to COM and SEG outputs of the driver to control the LED array via opamp drivers (instead of an LCD pixel array).

    In 1/2 bias mode,
    1) When a pixel needs to be turned off, COM=SEG=1/2Vdd. We use this to have no Opamp drive to the LED and consequently no LED turnon.
    2) When a pixel needs to be turned on, COM=0 and SEG= Vdd. We use this to have a drive from the Opamp and consequently the LED turnon.

    An advantage with this idea of using an LCD driver to control LED are -
    1) LCD drivers usually are available to control a lot of pixels - which translates to lot of LEDs in your application.
    2) It is fairly simple to set-up communication between the processor and the driver (SPI or I2C).

    Cheers
    Karthik
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  • davidjones333

    MemberOct 30, 2008

    Use of Rolling LED display, By loading a single pulse into the shift register at a time,therefore 1 every 16 clock cycles, all the outputs of the shift registers will turn on sequentially. Each output from the shift registers is connected to a transistor which, when on, conducts the cathode of each LED to ground. Consequently, one column in each block is activated on each clock cycle. The initial pulse to the shift registers must be regenerated every sixteen cycles.
    ---------------
    David Jones

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  • neo1786

    MemberOct 30, 2008

    hey thnx a lot davidjones333........i got it!!!!!!!!!
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  • Alisdead1

    MemberJan 24, 2010

    Вы знали, что <removed> для наружной рекламы могут быть статичными и мобильными?

    Admin Note: Language of the forum is English.
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