Interfacing 5 in (124mm) Seven Segment Display

Discussion in 'Embedded Systems and Microcontrollers' started by Ice_Blue, Aug 5, 2014.

  1. Ice_Blue

    Thread Starter New Member

    Jul 28, 2014
    Hello Guys

    I am new to the forum and I have just begun learning a bit more about microcontrollers.

    I am working on a project to drive an industrial type seven segment display. I got the code running on the prototype which i used small 12mm displays. Now the challenge is interfacing the hardware with the big 5 in displays. I am tring to drive the LEDs using the ULN2003. When I make measurements on the multimeter The seems to be nothing much happening @ the output. I have an input of 4.85 V and an output of 0.6V from the ULN2003.:confused:

    Can you please assist
  2. pwdixon


    Oct 11, 2012
    Need a circuit diagram of what you are doing.
    Probably a part number for the parts that worked and a part number for the parts that don't work would help too.
  3. MrChips


    Oct 2, 2009
    ULN2003 is an inverting driver. Also it has open collector output.
    Need circuit diagram in order to provide help.

    BTW where did you get the 5" displays?
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Ditto, where did you get the display? Love em. Have no need but might get some anyway. ;-)

    Also, having the spec for it lets us see how to drive it. Knowing "UNL2003" is only half the story.
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5 inch displays like that often have a Vf of >10v.

    It might be as simple as needing a higher voltage PSU. :)
  6. elec_mech

    Senior Member

    Nov 12, 2008
    Welcome to AAC.

    As THE_RB said, I'd guess you're using too low a voltage. 5" displays will require more than 5V to operate.

    Looks like Futurlec.

    If this is the case, those require 9.25V according to the website (though be leery, they've posted incorrect data before).

    A ULN2003 is only going to work with a common anode (CA) display. Is yours common anode or common cathode?

    Assuming CA, if I'm doing my math right (it's late), you could feed the CA pin(s) 12VDC, then connect each cathode segment in series with a 100-150Ω resistor to each ULN2003 pin. Make sure pin 8 of the ULN2003 is connected to ground. I'm assuming your micro takes 5VDC. This will work as long as you tie the GND from both the 5VDC and 12VDC supply together.

    How are you taking this measurement?

    As others have said, a schematic showing how you've got everything connected will help us help you immensely. If nothing else, sketch something on a napkin, take a picture, and post it here.
  7. pwdixon


    Oct 11, 2012
    Surely if the OP didn't have enough volts then the picture he posted wouldn't have had the LEDs lit?
  8. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    Interesting point. Let's assume it's not a power issue for a moment.

    The OP stated that with an input (to the ULN2003?) of 4.85v his output was 0.6v. To be expected as noted in elec_mech's post. And assuming the display is common anode, all segments would be lit as in the picture. I'd be interested in the case where the circuit outputted a mix of 4.85v and 0v.

    I'd REALLY be interested in a schematic!
  9. MrChips


    Oct 2, 2009
    Post #2, #3, #6, #8 and #9

    all would really like to see a schematic!