7 segment display total confusion

Discussion in 'General Electronics Chat' started by RodneyB, Dec 19, 2012.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    I am trying to make a novilty number to be displayed on our post box. I have a dual seven segment display KingbrightDA56-11EWA. Common Anode right hand decimal.

    As I wanted to be able to display severalnumbers I am trying to drive the 7 segmentdisplay with a SN74LS47N Which is A BCD 7 Segment display driver Yje Datasheet shows a maximum 15 Volts. Is that the maximum supply voltage for the IC.

    I Have Pins 4 & 5 B1/RB0, RB1 ( both on data sheet have lines shownabove them and I have no idea what that means or how to show it here. ) connected to the positive.
    Pin 3 LT (Again with a line able it ) can be switched to goto the positive
    Pins 1,2 6,7 B,C,D,A Can be switched on to the positive or off .
    The pins to the 7 segment display are connected through a 150R resistor. The common on the Display is connected to the +ve.
    I have connected a 5 Volt supply andnothing happens.
    I have removed the IC and Taken a jumper from the Negative through each resistor and each segment lights up. But Icant get it to work from the IC and nervous to increase the voltage from 5 volts,I cant seemto findthe correct supply voltage.
    Assistance willbe appreciated.
    Thanks
    Rodney
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,221
    It's rather difficult to follow your circuit description. Can you post a circuit diagram?
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,415
    3,354
    Do not increase the voltage above 5V.
    Post a circuit diagram.
    Post a photograph of your wiring.

    Did you connect pin 8 to GND and pin 16 to +5V?

    Temporarily connect pin 3 (Lamp Test) to GND and you should see all segments light up to display 8.

    You cannot simply connect switches from +5V to A, B, C, D inputs because TTL inputs will float high.
    You can either use 100 - 220Ω pull-down resistors or a better solution is to put the switch to GND and use 1k - 4.7kΩ pull-up resistors.

    How many digits do you need and what number do you want to display?
     
    Last edited: Dec 19, 2012
  4. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    I will post a diagram of the project thanking you in advance
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Please see the drawing as requested
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,415
    3,354
    The LED shows CC on pin 6. I presume you meant CA as in common-anode.

    Don't wire the switched to +5V. Wire the switches to GND (pin 8 of 74LS47)

    and close the LT switch at pin 3 (to GND) and tell me what you get.
     
  7. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    I connected all the switches to the negative .

    Pins 4 & 5 connected To the Positive

    Pin 3 connected to the negative and switched on and all the segments come on showing the figure 8.

    Pin 3 switch off all segments off

    Then its strange what happens next

    according to the data sheet

    B= L
    C=L
    D=H
    A=H

    shouldgive the digit 3

    Howeverit displays a 6

    I went through allthe combinations shown on the data sheet and nothing corresponds.

    I connected pins 4 & 5 to the negative and nothing came on. Conected them backtothe positive Lamptest works and Still get 6

    Thanks

    Rod
     
  8. absf

    Senior Member

    Dec 29, 2010
    1,490
    371
    D_C_B_A = "HLLH" = 1001 bin =9 dec

    Could it be 9 instead of 6?

    Allen
     
  9. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    I wish the decimalpoint is at the bottom right.and no other numbers come out
     
  10. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Many thanks for all the help I had a join between 2 tracks and I was making a mistake reading the data sheet forthe numbers. I just want one last piece of advice! I want to add some spark to this so want to add some routine to the display using a PIC12F675. If the Pins on the pic are low, will the 7 segment displaystill light up with out damaging the PIC. I want to Run the routine on the pic, lighting segments on the display and eventually counting down tothe desirednumber.
     
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