Power for 7 segment display COMMON CATHODE

Discussion in 'The Projects Forum' started by dyeraaron, Nov 11, 2008.

  1. dyeraaron

    Thread Starter Active Member

    Oct 27, 2008
    lets say we have a 7447 powered up through its Vcc and Gnd all good and its got its highs and lows tied in through the gates.....wouldn't that at least show some kind of illumination on a COMMON CATHODE display...the part number on the display is all funky but its orientation on the back of the cardboard package states its a common cathode.......this means two Grounds right? pin 4 and 12 are common cathode...please help...I need to at least turn these on then i can start from there.
  2. dyeraaron

    Thread Starter Active Member

    Oct 27, 2008
  3. k7elp60

    AAC Fanatic!

    Nov 4, 2008
    The 7447 is designed for common anode displays as the segements are turned on when the 7447 outputs go low.
    The NTE3057 has the common cathode pins as pin 2 and pin 9.
    Here is the pin layout:
    PIN# Function Pin# Function
    1 no pin 14 no pin
    2 Common Anode 13 Anode A
    3 Anode F 12 Anode B
    4 Anode g 11 Anode C
    5 Anode E 10 Anode D.P
    6 Anode D 9 Common Cathode
    7 no pin 8 no pin

    I suggest you use a CMOS decoder driver such as the CD4511 as it is for common cathode displays.
    You would connect pins 2 and 9 together on the NTE3057 and connect them to ground. The connect individual resistors between the anode pins and the 4511 outputs.