i want to use 4 big 7 seg

Discussion in 'General Electronics Chat' started by alitex, Jul 14, 2008.

  1. alitex

    Thread Starter Active Member

    Mar 5, 2007
    i have a project in AVR(attiny2313) and i want use 4 big 7 segments,what is the most suitable circuit for link 7 seg with my circuit....
    note:i have 2 voltages 5,12 VDC
    plz. help
  2. Wendy


    Mar 24, 2008
    You'll need to multiplex them. Something like a CMOS CD4511 for a decoder would also be helpful, I believe the data sheet here has some good suggestions. That and some darlingtons to handle individual digits.

    Just searching I found this website.

    I found the datasheets through the electronic resources forum.
    Last edited: Jul 14, 2008
  3. SgtWookie


    Jul 17, 2007
    Be careful with those big 7-segment displays. You really need current regulation for each segment.

    I bought some red 4" 7-segment displays from an online auction. Segments a thru g required about 11.4 Vf (forward voltage) for 25mA, and the DP was 5.7Vf at 25mA.

    You CAN use resistors, but verify what your Vf is for each segment using a constant current source before you hard-wire them in.

    After you verify Vf, then:
    Rlimit = (VoltageSupply - Vf) / LEDcurrent
    Then calculate the wattage required for the limiter resistors:
    W(Rlimit) = (VoltageSupply - Vf) x LEDcurrent x 2
    Then round up to the next higher wattage resistor available (eg: 1/10, 1/8, 1/4, etc)
  4. alitex

    Thread Starter Active Member

    Mar 5, 2007
    thanks alot,