How To Mount 7 Segment Displays?

Discussion in 'The Projects Forum' started by JDR04, Jul 26, 2011.

  1. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Who can tell me how to neatly mount 7X 7 segment Displays? I am looking for a way I can neatly do the wiring or tracks for the displays ie what connectors can be used etc. I'm not too concerned at this stage as to how to mount the module in a box yet but suggestions will always be appreciated.

    Is there a way to neatly do tracks to a connector of some sort and then physically connect the display module by way of wiring etc.?:confused:
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Well, usually one would mount them on a printed circuit board, and most frequently the drive circuitry is on the same PCB. If for some reason you need the display mounted remotely from the drive circuit, you could use dual row headers and flat ribbon cable w/plug connectors to get the control signals to the displays.
     
  3. debjit625

    Well-Known Member

    Apr 17, 2010
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    We call it PCB bar or PCB connector,I already used them to do that.
    [​IMG]

    Here is a pic for the connectors male and female
    [​IMG]

    Good Luck
     
  4. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks Sgtwookie, is there any chance of a photo or schematic of the tracking? I'd like to see how its actually done? Thanks again JDR04
     
  5. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks debjit625, it looks really neat the way you have done it. Any chance of a photo of the underside so I can see how you connected all the pins up.Thanks again.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Well, the wiring/traces will be very different, depending on the particular display model, manufacturer, etc.

    Do you have a part number for the LEDs in question? They are normally marked on one of the ends.

    If you don't have a part number, then we'll need a lot of information about your displays, and you will have to do some testing using a multimeter that has a diode test function.

    Do you have such a multimeter? If not, Harbor Freight sells them for a few $
     
  7. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Some 7-segment displays will fit on wide IC sockets.
     
  8. debjit625

    Well-Known Member

    Apr 17, 2010
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    You don't need IC socket,FNDs have their own base available in market.


    That’s a varoboard and the connections are quite complicated, looking at a pic you will not get it. And another thing even a schematic can't help you as their are many different FNDs with different rating as Sgtwookie said, so the circuit will depend on your FND.

    Try to figure out which kind of FND you are using...and post the details here so we could help you.

    Good Luck
     
  9. KJ6EAD

    Senior Member

    Apr 30, 2011
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    What's FND? Do you have a link to one of these bases you speak of?
     
  10. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Hi SgtWookie, I'm using common cathode 7 segemnt displays. I dont know how to attach the datasheet so I'll try and insert a link to the datasheet.

    http://docs-europe.electrocomponents.com/webdocs/0200/0900766b802001c1.pdf

    I hope the link works.
    My overall objective with this display is to have it as a module on its own so when I mount it in a box I have a degree of flexibility with positioning etc.

    I have a Fluke 179 meter. Do you still need me to do some testing of some sort?

    Anyway, thanks for your time and help, I appreciate it. Cheers JDR04
     
  11. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Hi debjit625, I'm a newbie so could you tell me what is a FND please? I'd be keen to see a photo of the underside just to get an idea of the principle of how you did it. I've figured out that the wiring will be different due to the different types of connection etc but an idea of how you did it would be appreciated. Thanks again.
     
  12. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Is a "FND" refering to a "Fairchild Numeric Display"? Was someone using that acronym to refer to a 7-segment LED numeric display? :confused: Kinda like saying you made a Xerox of something, rather than a copy of something? ...or that you used a Kleenex rather than using a tissue?
     
  13. debjit625

    Well-Known Member

    Apr 17, 2010
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    FND means Fundamental Numeric Display, but it’s quite old and not used much instead seven segment display (SSD) is used. I did that many years ago even I can't find the schematic right now (I will try),anyway here I found the underside photo ,just after soldering the components.
    [​IMG]

    I will try for the schematic later,BTW I was using common anode SSD.

    Good Luck
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    I didn't have a model for your exact 7-segment LED, but this one is the same pinout, just a different size.

    [​IMG]

    That's more or less the way it could be done for a commercial board, except I'd put the 10-pin ribbon cable connector on the other side of the board so that the display could mount flush.

    [eta]
    Here's the pin layout for your display from the datasheet:

    [​IMG]

    I eliminated the common anode schematic; now you just have yours to look at.

    You will need to use one resistor per segment resistor between whatever you use to power the segments, and the segment leads. What size resistor you need depends upon what the displays' Vf (forward voltage) at the rated current is, and what voltage you will be powering them from.

    I don't know what you want to control the display with, but you'll need something like a microcontroller or a decimal-to-7-segment display decoder IC.
     
    Last edited: Jul 28, 2011
  15. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks SgtWookie, that's a really neat schematic drawing you have done. Appreciate the other info as well.What software is that you used? I'm using 4026's to drive my displays, seems easier and cheaper to do than using two IC's to drive one display.

    My problem is that I have 7 segments to wire up and I'm completely lost as to how to do the tracks for a neat job. I like the way your display tracks go to a connector, its really neat. I could figure out to do two with the tracks coming out the sides ie a sort of mirror image of your one but when there are 7 displays altogether, help!!! Cheers JDR04

    I'm building this circuit as an excercise to learn about electronics. Eventually I will use it to test how many times a switch will work before it fails. I think there will have to be some sort of interface between the counting circuit and the pulses from the switch but that will be my next stage of learning.
     
  16. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks debjit625, wow that's a really neat job you've done. Thanks for the photo.
     
  17. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
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    I have listen this many time what is the full form of FND??
     
  18. SgtWookie

    Expert

    Jul 17, 2007
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    It was kind of thrown together really quickly. I didn't spend much time thinking about what pins on the ribbon cable connector would work for the trace routings the best.
    I used Cadsoft's Eagle. It takes awhile to get good with it, but it's pretty powerful. In the "free" version, you're limited to two board layers, a board no larger than 3" x 4", and 1 schematic drawing per filename. You can still do a lot within those limitations, though.
    You really ought to have a look at using 4553 & 4543 IC's instead. The 4553 is a 3-digit decimal counter, and the 4543 can drive three 7-segment displays; so that's two IC's for 3 displays. You cut your IC count by 1 for every 3 displays. Also, since the displays are multiplexed, it simplifies the wiring quite a bit. You will either need to use a 2-sided board, or lots of jumpers though.

    It's a lot easier when the displays are multiplexed, as the a thru g pins are shared between three displays; just the common cathodes have their own traces.
    Here's a link to an OnSemi (formerly Motorola) datasheet for the MC14543B:
    http://www.onsemi.com/pub_link/Collateral/MC14543B-D.PDF
    and the 4553:
    http://www.onsemi.com/pub_link/Collateral/MC14553B-D.PDF
    For starters, look at this last link first, on page 6.
    It shows how to wire up six 7-segment displays using 4 IC's (two 4553, two 4543) and three transistors.
    If you really want to extend the display beyond 6 digits, the wiring might get messy.
    Then have a look at the 4543, page 6; it shows the basic connections for common cathode and common anode 7-segment display - just a single segment.

    Well, testing switches will be a whole 'nother subject. So, just focus on how many digits you really want to display at the moment, and with this "new information", what approach would you rather use?
     
    Last edited: Jul 29, 2011
  19. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks SgtWookie, your info is great and I will certainly go through it. Your suggestion for other IC's is appreciated and I will check it out. It looks like my life will be made a lot easier.Thanks again. Its guys like yourselves that make this forum so great for newbies such as myself.
     
  20. SgtWookie

    Expert

    Jul 17, 2007
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    Sure.

    Just to show you one way the routing could be accomplished, I manually routed this example using Cadsoft's Eagle. I didn't route the common cathodes from each display to the transistors yet; it was just sort of a "fun" exercise. The red traces going horizontal are on the top of the board, the blue traces are on the bottom. The green areas are "pads" or "vias" that go through the board.

    The order of the segments on the traces extending to the right is:
    b
    f
    g
    c

    e
    d
    c
    DP
    But, the way I routed it, they could be reassigned in any order. Eagles' Autorouter will connect them up with far fewer vias than I used; this is just to show you one way that it can be accomplished, and I'm not terribly fond of the autorouter, as it connects things but the results frequently leave much to be desired. I was seeing if I could fit all of the traces required between the pins, but there was not quite enough room using a 50 mil (0.05") grid. There would be plenty of room if I changed the shape of the pads for the displays
     
    Last edited: Jul 31, 2011
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