Large Seven Segment Display Project

Discussion in 'The Projects Forum' started by emporiumx, Feb 16, 2007.

  1. emporiumx

    Thread Starter Member

    Feb 16, 2007

    I am building a rate counter that uses a photosensor/reflector type system to detect cans passing a point on a factory line.
    I am using an ATMEGA8535 Micro to do most of the work and outputting to either 3 or 4 separate 4511 (BCD to 7 Segment) and through a ULN2003(per display) to the 2 inch (50mm ish) display segments. (Common Anode)

    My Question is? Of course the ATMega and the 4511 will be working on 5v however the displays are on 12v (Each segment requires 8v to run). Is pin 9 on the uln2003's tied to the 5v or the 12v? Also is there any problem to tie the pin 9's from multiple displays together? (I am guessing it is ok to tie then together and to the 12v but why I ask is because I saw a design for such an application with the pin 9 floating so I want to make sure before having boards manufactured).

    Also I have found a pretty reasonable pcb house in china to make my boards (all through hole components) but can anybody suggest any other reasonably priced placed to get small runs of pcb's done?


  2. mrmeval

    AAC Fanatic!

    Jun 30, 2006
  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    The best practice is to tie pin 9 of the ULN2003 to the positive supply to your LED displays. They will be tied together in this case and that is OK.
    Check into SierraProtoExpress . I think they still have low pricing on low-volume 2-layer through-hole boards.

  4. emporiumx

    Thread Starter Member

    Feb 16, 2007
    THanks for your replies. What you are saying is as I suspected but I needed to make sure. Thanks Heaps.

  5. dionaide

    New Member

    Jul 30, 2007
    thanks for this forum...