Can't get 7-segment display to work

Discussion in 'General Electronics Chat' started by iFunk, Apr 10, 2018.

  1. iFunk

    Thread Starter New Member

    Apr 6, 2018
    Hi there, I'm trying to learn about 7 segment display, but I can't get any of the segments to light up, I am using a 12V supply from my power supply going into a 330ohm resistor. Currently, I have the resistor attached to pin one and the I am from pin 8 (which is common with pin 3) to the negative of the power supply.

    I was expecting that this is all I needed to get one of the segments to light up, but nothing. I'm more inclined to think I have made a mistake than the display is faulty, as I have two of them and I can't get any of them to light up. What am I doing wrong?
  2. ericgibbs


    Jan 29, 2010
    hi iF,
    I guess you know there are Common Anode and Common Cathode type , 7 seg LED's, which type is yours.?
  3. iFunk

    Thread Starter New Member

    Apr 6, 2018
    So the 7 segment I have is an A52-11EWA so I think it's common Anode? have I got that right?
  4. LesJones

    Well-Known Member

    Jan 8, 2017
    You have the polarity the wrong way round so there is a good chance you will have destroyed the segments of the display you have tested so far. When you test it with the correct polarity you will be slightly exceeding the maximum current rating. I suggect running them at about 20 mA.

  5. dl324

    AAC Fanatic!

    Mar 30, 2015
    You have the polarity backwards. Connect the common anode to the power supply through a 1000 ohm resistor (this will limit current to a more reasonable 10mA). Then connect one of the segments to ground.
  6. iFunk

    Thread Starter New Member

    Apr 6, 2018
    Thank you, it worked, one other issue I had was that the bread board I was using had some duff pins, this was what was causing much of the problem trying to get this going. When I put the right way round, it was indeed pulling 29mA, but reducing Voltage down to 5A put that down to 9mA and the segments light up fine. Thank you very much for your help.