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4 x 7 segment common anode

Discussion in 'Microcontrollers, Programming and IoT' started by Rajinder, Apr 9, 2019.

  1. Rajinder

    Rajinder

    402
    7
    Jan 30, 2016
    Hi
    I have a 4 x 7 segment common anode display, which i will be driving from a PIC micro.
    I need some help in calculating resistor values and selecting the correct PNP transistors.
    Can anyone help?
    Thanks in advance.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,306
    1,889
    Nov 17, 2011
  3. Rajinder

    Rajinder

    402
    7
    Jan 30, 2016
  4. Rajinder

    Rajinder

    402
    7
    Jan 30, 2016
    Are there any considerations required for the transistors? Also if i light up segments to say display the number '8'. Do i calculate each segments current to get the overall current?
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    9,306
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    Nov 17, 2011
    The transistors are used in on/off operation only. You need to match max. current and voltage, that's more or less all.
    Each transistor drives one segment only.
    The total current (per complete display) is relevant for the power supply.
    Plus you'll have to consider total current (per digit) when multiplexing the display for the transistors (per digit) that drive the common anode of each digit.

    See for example here. Post your own schematic for us to cross-check.
     
    Rajinder likes this.
  6. Mark2019

    Mark2019

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    Jul 7, 2019
    Rajinder likes this.
  7. Rajinder

    Rajinder

    402
    7
    Jan 30, 2016
    Thankyou.
     
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