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Wire Wrap

Discussion in 'Electronic Basics' started by GT, May 23, 2005.

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  1. GT

    GT Guest

    I would like to wire wrap some small hobby circuits. I figure 30AWG is
    correct for me. I see Digikey (http://dkc3.digikey.com/PDF/T051/1323.pdf)
    has regular wrap and modified wrap. Which one is best to use?

    Also I saw a post that suggested wire wrap is obsolete. I can not imagine
    how that could be because it seems perfect for small prototype and hobby --
    do others out here wire wrap? Is there a better way to do small hobby stuff
    (I do like breadboad but some stuff I'd like to keep for a while and so
    wirewrap seems better).

    Thanks for any advice.
     
  2. BUt you might start by saying why you think it would be good
    for the hobbyist.

    Real wire wrap is multiple turns of wire around leads intended for
    wire wrap, and it counts on the wire biting into the leads for good
    contact. You need IC sockets that are long enough, and if I recall
    properly, the leads of those sockets should be square. Done
    badly, it can add to problems, and note that while wire wrap was once
    common, it's not happening much anymore. I don't think anyone felt it was
    particularly good for analog, and one does not see real wire wrap done on
    resistor or capacitor leads, one sees those soldered or plugged into pins
    that can be properly wire wrapped.

    I would guess you think it's good for the hobbyist because the
    wires can be unwound if you want to change things, or reuse the parts.

    But soldering is not a problem, once you get used to it. And when
    components aren't big and heavy, there's little need for a mechanical
    joint before the solder, so you can just tack solder the leads together.
    Then they are very easy to take apart when needed.

    One of the best routes for the beginner (and oldtimer) is to take
    a piece of copper circuit board, and use that as the "chassis". Every
    ground connection is soldered to the board, and then the parts reside
    above that copper ground surface. Usually, there are enough leads
    to ground to support the other components. It's really easy to change
    things, and there is ample lead length on the components for
    making most of the connections. Some scrap wire does the rest. YOu
    get a very good ground surface this way, and unlike something like
    perfboard, you don't require much effort to change things.

    Of course, you may not be asking about real wire wrap. There were
    things referred to as "wire wrap" where one twirls the wire around
    a component lead, but then you do solder the joint. But it actually
    ends up being quite cumbersome to remove components.

    Michael
     
  3. Graham Knott

    Graham Knott Guest

    --
    Have a look at http://homepage.ntlworld.com/g.knott/elect97.htm


    My most uptodate website is
    http://homepage.ntlworld.com/g.knott/index.htm
     
  4. Chris

    Chris Guest

    Wire wrap is fairly easy, but has a bit of a learning curve, and is
    difficult to do well.

    As another post mentioned, the process involves twisting wire (usually
    30AWG) around a square wire wrap post with a wire wrap tool. If the
    job is done right, the edge of the wire wrap post will bite into the
    surface of the wire, galling it and creating a cold weld. (You can
    feel whether a wire wrap is good by unwinding it. If you've done it
    right, the wire will pull as you unstick the gall for each quarter
    wind.) If the job is done right, the cold weld joint is sturdy and
    should take the same abuse as a solder joint while maintaining a good
    gas-tight electrical connection. You require special wire wrap sockets
    for everything you're wire wrapping, or you can solder connections to
    discrete components and just use the special sockets for ICs. If you
    do get those, make sure you buy the sockets that have 3-deep posts.
    Otherwise, you'll run out of room unless you really think out each
    daisy chain first. Obviously wire wrap IC sockets are quite a bit more
    expensive than plain IC sockets.

    The problem is doing it right. Most hobbyists working with a small
    hand tool end up with intermittent electrical connections and a lot of
    frustration in trying to debug, not to mention nicked and easily broken
    wire ends where the insulation strip was a little aggressive. As an
    extra added bonus, a poor wire wrap frequently results in unwinding a
    lot of stuff in very cramped quarters, with the possibility of
    disturbing adjacent wire wrap joints. (This is covered in the link
    shown in another post.)

    You can see where this is headed. I feel a hobbyist should stick with
    soldered connections. A good place to start for newbies is a perfboard
    with a layout similar to the protoboard you're probably already using
    to check circuits out. Radio Shack sells a perfboard with 4-pad 0.1"
    spacing, just like your protoboard. It's the same size as their small
    protoboard, and you can transfer your circuits right over from one to
    the other. If you've got a small soldering iron, some solder, and some
    24- or 26-gauge solid wire, you can do this easily. It will also give
    you some additional practice in soldering.

    Good luck with your projects.
    Chris
     
  5. Good advice above.

    There are other methods which can be combined in any way you like.
    The goal is to connect two or more points (nodes) with another
    electrically. Exactly how it is done is less important.

    I often take a piece of copper laminate (pcb material) and clean it
    with a kitchen sponge, the abrasive type.
    Then I use a sharp tool, like the end of a file, and make grooves in
    the copper surface, dividing it into small squares.

    I make more squares than I expect I will need.
    When you experiment you need space, so try not to cram things together
    too much.

    Then I can solder components between these copper "islands".
    Modern surface mount components can be used, and older components too,
    by cutting and bending the wires and soldering them to copper islands.

    By avoiding holes we save ourselves a lot of extra work and machinery
    for drilling. Or expensive prototype boards with pads and holes.
    (but this type of board is also a good alternative, it is just a little
    more expensive than buying pcb material in some surplus shop)

    In this way I can experiment, move and change components, and the
    circuit will be in a usable state afterwards.

    I bought a solderless protoboard once, but I never use it, because I
    hate having to take circuits apart and rebuilding them a second time.
    By experimenting by soldering you get a result which is directly
    usable, or if you want to save your experiments.
    The same circuit can come in handy later, so I save all experiments.
    I might also need a special component which I can take off an earlier
    experiment.

    Circuits which are to be used are placed in a box, so it doesn't matter
    much what the circuit board looks like, it is the function which is
    important.

    Forget about wire-wrapping. It is a very complicated way to connect two
    points electrically, it is expensive, needs special sockets, wire and
    tools, and is simply antiquated. You cannot use modern smd components
    with wire wrapping. We as hobbyists or experimenters will need to use
    both smd and old components for a few decades, until there are no more
    wire components in the surplus shops and in our shelfs.

    So use a method which can use both types of components.

    Later you will need to learn about etching and making custom made pcb's
    for yourself, but that is for circuits you need to produce more than
    one of, or if you need to miniturize a circuit.
    Etched pcb's are not suitable for experimenting so you still need the
    methods above for experimenting.

    Some people skip the experiments with real components and use a SPICE
    simulator in the computer to experiment, test a circuit, then design a
    circuit board, print out, etch it into copper laminate, build the
    circuit.

    Others think it is more fun to sit at the workbench with a soldering
    iron in hand, building as you like for the moment, see what happens :)
     
  6. Tom Woodrow

    Tom Woodrow Guest

    I don't want to get into the argument about a hobbyisy doing or not
    doing wire wrap. I have used ww for about 30 years and still use it
    ocassionally.

    A "regular" wire wrap wraps just the wire around the post. This provides
    sufficient strength for 26 ga. BUT for 30 ga you would want to use the
    modified wrap. The "modified" wrap is setup to wrap about 1 1/2 to 2
    turns of the kynar insulation around the base of the wrap to provide
    support (strength) for the wrap. After the insulation wrap comes the
    wire wrapping.

    The downside of the modified wrap id that it gives you a very small
    inductor at each termination, so this may not be very goot for ultra
    high frequency circuits and you may need some extra termination (r/c) on
    some lines to prevent ringing (not that likely, but I have seen it happen).

    Tom Woodrow
    www.dacworks.com
     
  7. Byron A Jeff

    Byron A Jeff Guest

    Modified wrap. However I wouldn't buy anything from off that Digikey page.
    Wow that's expensive!

    I still wrap boards with the handy dandy manual tool from Radio Shack.

    http://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=276-1570

    Not fancy but gets the job done.

    As for wire, the RatShack carries red, white, and blue. I get other colors
    locally here in Atlanta. However if you need mail order then
    Jameco has a good deal. Here is their catalog page:

    http://www.jameco.com/Jameco/catalogs/c252/P88.pdf

    Wire wrap sockets are on page 111.
    Yes. Like everything else it has its advantages and disadvantages. When
    properly done wire wrap is stable. I have WW boards in use that are
    approaching 10 years old. Also WW is usually easy to fix as wires can
    be unwrapped just as easily as they are wrapped.

    On the down side sockets are expensive. 3 level wrap will triple the
    depth of your board. Managing individual components can be problematic.
    Header plugs such as the one listed on page 112 of the Jameco catalog
    are helpful in this regard.

    But it certainly works. You can see a sample of my handywork on my PIC
    Designer: http://www.finitesite.com/d3jsys/picdesigner/underside.html

    Again it's debatable. I find that I get to frustrated with soldering
    screwups to do it consistently. That's why I've never moved permanently
    from wire wrap.

    I would advise you to get into wire wrap cheap (leave DigiKey alone!)
    and give it a whirl.

    BAJ
     
  8. Guest

    One other method for prototyping, which is probably the cheapest
    imaginable is this: One piece of softwood and a box of coppered nails
    (sometimes called hardboard pins).
    Draw the circuit on the timber, and drive a pin into the wood at
    connection points. The pins can be linked together by wire, soldered at
    each pin. Components are connected by the same method.
    It's cheap, and relatively robust (better than building a 'christmas
    tree' in mid-air). It's a method I always use for initial circuit
    ideas.

    - Martin T.
     
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