Help with displaying on Double 7 segment Display

Discussion in 'The Projects Forum' started by Xtasy, Mar 26, 2009.

  1. Xtasy

    Thread Starter New Member

    Mar 26, 2009
    1
    0
    Hi,

    I was wondering if anyone can help with pin layout to create a double 7 segment display. I have a MAN6940 Double 7 segment display which is cathode to cathode. AND a cathode to cathode decoder part # CD4511BC and I have two of these since each decoder can only decode up to 9. So, the idea is to have four inputs (represented by 4 wires) such as 0000 which in turn will display 0 on the double seven segment display and for 1111 it will display 15 on the double segment display.

    Just giving me a general idea would of how to do this also would be helpful. Thanks.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK, just a quick bit about nomenclature.

    The MAN6940 is a common cathode 7-segment display.
    You can obtain a datasheet for it here: http://www.datasheetcatalog.com/datasheets_pdf/M/A/N/6/MAN6940.shtml

    The 4511 can drive common cathode 7-segment displays.
    However, it will only output numbers 0 through 9 (BCD codes 0000 through 1001).

    You'll need resistors between the outputs of the 4511 and the 7-segment display to limit the current. The value of resistance in Ohms will depend upon what the Vf of the diodes in the displays are, the current desired through the displays, and your Vdd.

    You can multiplex the display if you wish. You'll have to connect output a to LED inputs a1 and a2, output b to b1 and b2, ... g to g1 and g2.

    You put a 4-bit BCD number on the 4511 inputs for 1/2 of the display, and then you sink current from that side's common cathode pin for a period of time. Then you stop sinking current from the pin, change the 4-bit BCD number on the 4511 inputs for the other half, and then start sinking current for the other half for a period of time. Then you stop sinking current from that side, and repeat the process. This is known as multiplexing. If the multiplexing rate is high enough, you won't see the flashing from side to side due to persistence of vision.
     
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