7-segment display

Discussion in 'The Projects Forum' started by marnus, May 8, 2013.

  1. marnus

    Thread Starter New Member

    Apr 10, 2013
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    0
    Hi

    I would like to get some information regarding 7-segment display unit.
    This is a project that im busy quite a time with now, and i see im going no where slowly...

    This display unit is from babcock, made probably in the 80's. It part number is
    SP-324 and SP-325, the one is a 4 digit display and the other one is a 5 digit display, i cant figure out the circuit because i have no idea where is the common/ ground pin. Here is the link http://www.babcockinc.com/babcock/documents/doc_3262.html

    so I can see 7 pins for the seven segments and th dp pins is there
    and 2 pins under the ring ( on the sketch ) wich is the keep alive and anode contact.

    I have made some circuits on circuit lab under the name "raised cathode 7-segment display" im not done yet with the circuit but suggestions can help

    Many Thanks

    Marnus
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,997
    3,756
    You realize these displays are high voltage and require about 180 volts. They are not simple LEDs. I don't know if you are we or experienced but, if new, you might want to start with a 4dighit LED display.

    I will wait to learn your experience level before providing any advice on high voltage displays.
     
  3. marnus

    Thread Starter New Member

    Apr 10, 2013
    4
    0
    Thanks for the reply.

    I have work with LED displays before, I understand them pretty much.
    I have interface them for flight sims before, I have look for simular LED size displays but could not find them that is why i want this one to work with my new interface board
    ( Open cockpit i/o display board )http://www.opencockpits.com/uploads/manuales/IOCard_Displays_II_Manual_2012_REV2.2_English.pdf.

    I am a student electronic technician working full-time bussy with my trade and part time student at varsity... I understand electronics
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,997
    3,756
    Well, they work very similarly to the LED but at higher voltage (be sure to limit current with appropriately sized resistors. Most displays that look like yours are running at 30 to 50 volts and are known as VFD (vacuum fluorescent displays). However, the voltage of your unit (180) is in line with Nixie tube technology. Again, limit current.

    Look for a 7400 series logic chip, either 7441 or 74141 as a BCD to Nixie tube display driver. Just push the bcd digit value to the logic chip and the chip will output to a-g segments.

    Good luck and stay safe.
     
  5. marnus

    Thread Starter New Member

    Apr 10, 2013
    4
    0
    Hi thanks for that info, i did some research last night on it... I still need to think of a good way to generate a good supply of 160 v..maybe building a transformer?

    This is how i think the old system used to work http://www.cheekytronics.com/Projects/7447_BCD_7_seg_driver.html

    The reason, this is what is in the old interface board.

    A High voltage cathode driver SN75480
    Single bipolar timer NE555N

    So if i want to test the display where do i put the ground and the live (wich pins )

    Thanks for the help.
     
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