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neo1786 • Oct 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
reachrkata • Oct 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).

davidjones333 • Oct 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

neo1786 • Oct 30, 2008
hey thnx a lot davidjones333........i got it!!!!!!!!!
Alisdead1 • Jan 24, 2010
Вы знали, что для наружной рекламы могут быть статичными и мобильными?

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