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What are these things called?, Newbie question...

Discussion in 'General Electronics' started by bigbossfan80, May 14, 2004.

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  1. bigbossfan80

    bigbossfan80 Guest

    I don't really know a lot about electroncis, and therefore since I
    need an answer to something I figured I would start here...I hope
    there's some experts here!:)

    Basically I have taken apart something called an AutoXray(no need to
    know what it is). The AutoXray has an LCD screen/display. The display
    is connected to the main part of the electronics which houses all of
    the IC's and chips etc. It is connected using some type of light-green
    plastic that looks like it has 8 or 9 thin, flat metal lines running
    through it. I'm guessing that these metal lines are basically acting
    the exact same as wires would, except they use these instead because
    it saves a ton of room.

    So basically I have two questions. One, do these green, plastic things
    with metal lines running through them actually have a name. And two,
    since I want to extend the length of the LCD screen from the "brain",
    can I just use regular wires to do so?


    I wish I had a picture but I don't...I tried searching online but
    couldn't find I hope what I said makes sense!:)
  2. Don Bruder

    Don Bruder Guest

    I've always heard them called "zebra strips" (for reasons that should be
    pretty self-evident) but if they have some other "official" name, I
    don't recall ever hearing it. As far as moving the display somewhere
    else, yes, you could do that. As you suspect, the main concept behind
    the zebra strip is "compact connection" - The metal lines are exactly
    what you think - "wire subsitutes".

    What I'd do is etch a small board (a little bigger than the LCD panel)
    with pads that match the pads the zebra strip connects to on the main
    board, connected to holes to solder wires to, then use the zebra strip
    to reconnect the LCD to the "mini board" you've made, and solder the
    wires to the corresponding pads/holes on the main board and mini-board.

    I'm guessing, from what you're playing with, and what you're asking,
    that you're looking at dash-mounting the AXR's display (yes, I'm aware
    of what the item is - neat toys, if you've got an OBD/OBDII equipped
    ride - but total junk for me and my pre-OBD car) for "in motion code
    display" use, while the "brains" and ECU hookup hides someplace out of
    sight? If so, be sure to pay *REAL* close attention to how hot it can
    get in a car in the summer sun when you start looking for a place to
    mount it - You may find yourself with a cooked LCD that displays nothing
    if you put it in the wrong spot... Of course, you may just find yourself
    in the same situation if you mount it in the RIGHT place, since cars,
    especially dark ones (dunno if yours fits that category, but...) make
    such wonderful "solar ovens"...
  3. This could be one of two things. If the lines are flat and have
    some width to them, and you can kind of see through the plastic,
    then you have a flex-circuit, short for flexiable printed circuit.
    If the lines have a circular cross section, and do not really have
    any width to them, then you have a ribbon cable. As you suspect,
    the lines are wires imbedded in the plastic.
    You can try extending the wiring. What you might run into is that
    the wire spacing is critical to keeping the signals on each wire
    from interfering with the signals on the other wires. It is also
    possible that these wires are carrying signals that have frequencies
    that would radiate into other devices and cause interference if you
    attempted to run this device outside of the case that it was built in.

    If the device is FCC certified, you will certainly no longer be in
    a certified configuration. That means that you can probably get away
    with it for personal use, but you couldn't use it in commercial
    applications or resell the unit (at least no legally).

  4. Sounds like a flat cable- a cheap-a** one that uses low-temperature
    plastic such as polyester.

    Best regards,
    Spehro Pefhany
  5. Sporkman

    Sporkman Guest

    Actually it could be a third. FFC is short for "flat flex circuit" as
    opposed to FPC which is short for "flex printed circuit". The
    difference is that FFC are basically flattened wires laminated onto
    polyamide, and then overlaminated except for a short length at both ends
    where the electrical contacts are made. FPC is actually etched
    similarly to a printed wiring board and then overlaminated. Thus FFC
    results in ONLY straight lengths, whereas FPC can be made in all kinds
    of shapes and can even be an integral portion of a rigid PWB (called
    rigid-flex). The contacts for FPC can also be of a number of different
    types, including soldered pins. The contacts for FFC are always either
    low insertion force (LIF) or zero insertion force (ZIF) connectors which
    allow the unlaminated end of the strip to be inserted and held by
    friction. FFC strips are typically only supplied in a set of standard
    widths and number of contacts, corresponding with the available ZIP and
    LIF connectors out there. It's also going to allow only limited
    amperages and voltages because of the standard cross sections and
    conductor spacing. You can make the cross section for FPC anything you
    like, and also vary the spacing so that your flex piece can carry a
    wider range of amperages and voltages. An FPC manufacturer can,
    however, make FPC to fit into standard ZIP and LIF connectors, and
    that's quite often done.

    FFC is typically MUCH cheaper than FPC for (hopefully) obvious reasons,
    and it's much more commonly used. The flex piece for your typical print
    head on your typical printer is a good example of FFC. The color of the
    laminate could be almost anything, so whether it's green or transparent
    or white or whatever is no indication. If (as I suspect) the connection
    on one or the other end of the flex piece that you have is a ZIF of LIF
    connector, then you could make a small circuit card with a similar
    connector on it (see, and run wires from the other side
    of the card.

    Mark 'Sporky' Stapleton
    Watermark Design, LLC
  6. Hey Sporky, how long have you trolled here also? :)

  7. Err, maybe polyimide. I don't think I've seen polyamide.
    Polyimide is typically amber, very expensive (relatively speaking) and
    is solderable directly. If it's clear or green, it's probably
    polyester and uses some other means of connection most likely.
    That would be a way.

    Best regards,
    Spehro Pefhany
  8. Pszemol

    Pszemol Guest

    And what if this kind of flex tape connector is cracked and conductors are
    broken... is there a way to fix them with a some kind of conducting glue?
    What would you recommend?
  9. Externet

    Externet Guest

    The green fiberglass board with etched metal is called a printed
    circuit board; those etched copper lines are the equivalent of wires;
    the AutoXRay is a code reader for automobile computer error codes, and
    the display can be extended with wires to a limited unknown distance
    IF the existing wires are spliced, as connecting to the display
    directly may not be possible.
  10. Sporkman

    Sporkman Guest

    Yah, you could be right. I'm relying entirely on my memory, and I've
    been known to confuse a fact or two in my time.
    It probably IS polyimide, as you speculate. There are other laminates
    used on FFC, apparently, because I remember it as white. Molex sells
    the stuff I believe.
  11. Robert Baer

    Robert Baer Guest

    That is a flat ribbon cable,and it is the latest variation of that
    class of cables.
    Look in a computer and see one of the older variations used for the
    hard drives and floppy drives.
    THe variation you are looking at is also called a "flex" circuit.
    It is made like a PC board - copper on a flexible plastic substrate,
    etched for the pattern, and then more plastic laminated on top.

    In making your own replacement (i presume longer) cable, either use
    floppy ribbon cable, or take a number of wires and carefully lay them
    side by side on some packing tape, and stick more tape on top as
    The idea is to keep the wires uniformily close together (constant
    spacing) for a low and constant impedance.
    Keep the length as short as possible.
    You might need to tape copper foil to the home-made flat ribbon cable
    and connect that to ground, to reduce the impedance and signal
    distortions due to ringing.
    If you get severe "ghosts" in the picture, then add about 100 ohms in
    series with each wire comint from the source to the cable.
  12. Rich Grise

    Rich Grise Guest

    It could theoretically be fixed, but it'd be a considerable PITA. If you've
    ever soldered anythig, imagine trying to solder little .002" thick strips
    of metallization on a .010" plastic substrate. The only logical thing
    to do is either replace the whole thing, of if there's any meat on the
    connector ends, solder new individual wires along each trace.

    Good Luck!
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