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Making small PC boards

Discussion in 'Electronic Design' started by Palmer, Dec 27, 2004.

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  1. Palmer

    Palmer Guest

    I'm looking at either finding or making some small PC boards. They need to
    be about a 1/2 inch square. I'm wanting to mount an LED on each board but
    I'll need to connect 4 LED boards in series but each board will be connected
    to the next with insulated wires. I could either have a board with 4 holes
    right down the middle but then I would have a long length of wire for the
    negative side of the source. I was thinking of having a board with four hole
    on the upper half and two on the bottom half. The bottom two holes would
    just be a place for the negative wire coming in and one going out to the
    next board. The two center holes on the top half would be for the LED wires
    and the outer holes on either side would be for the positive coming in and
    one going out to the next board.
    So would it be easier to make a board as such or find something to work? I'm
    new at this so I'm looking for help and direction. The only thing is that
    the side the LED is mounted on to remain smooth so that means all the wires
    and LED legs to be soldered on the back side.
    Thanks for your comments and help.
    Palmer
     
  2. hamilton

    hamilton Guest

    Palmer,

    OK, the cost of a 1/2" x 1/2" PCB will cost a lot.
    Building a larger board and cut up into small pieces will be good.

    Using a vector board with the wireing you are looking for would be the
    easiest.

    If I understand your circuit each board would look like this:

    LED LED LED LED
    o--o-|<-o--o o--o-|<-o--o o--o-|<-o--o o--o-|<-o--o
    o----------o o----------o o----------o o----------o
    board 1 board 2 board 3 board 4
    Are the LEDs surface mount ?

    This would put all the LEDs in series.
    What does you power supply look like ??

    PS: Got to www.digikey.com and search for "vector board".
     
  3. Guest

    Why are you making a PCB if all that is going on it is a single LED? It
    would be more efficient to mount the LEDs in some kind of fixture (e.g.
    a matrix of holes drilled in a piece of metal, wood or styrene).
    Although you can etch a PCB to do this (I recommend Olimex,
    www.olimex.com, for this, since they charge by panel area rather than
    by number of PCBs). Or you could build it on snippets of regular matrix
    board. But as I said, I don't understand why you need a PCB for this
    application.
     
  4. Palmer

    Palmer Guest

    You are correct on how the boards will look and be arranged. ( I could have
    never drawn that on the computer)
    The power will be coming from the car in which they will be installed.....
    so it will be a 12 volt to 13.6 volt source. What I have seen are the LEDs
    that are bought at places like Radio Shack. They look like a small dome with
    a small flared bottom. What I am after is being able to drill a hole the
    same size as the LED and inserting it from the back side of the hole and the
    flared bottom and or the PC board stopping the LED from going any further
    in. That is also why would like all the wires and LED legs to be on the
    back side of the board.
    I tried searching for vector board but not too sure what that is and what
    I'm looking for. I've seen boards at R.S. that are just a bunch of drilled
    holes that I could cut down but I wasn't sure how to apply the connections
    between the holes...like a circuit board is. Like in your drawing ....the
    "--" are connected via copper trace...if that is what it is called.
    Again thanks for your help.
     
  5. Tweetldee

    Tweetldee Guest

    Well, you could do something like this...
    Arrange your boards so that you have right angle 2-pin female headers on one
    side, and mating 2-pin male headers on the other side. Then, you could join
    as few or as many as you like. No connecting wires except for the ones
    supplying power.

    --
    Dave M
    MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
    the address)

    Never take a laxative and a sleeping pill at the same time!!
     
  6. hamilton

    hamilton Guest

    A picture is worth a thousand words.
    Also tell others what you have in mind without knowing the terms.
    "Radio Shack" means you are in the US.
    Good, Yes you are correct, getting the boards and LEDs from Rat shack
    will get this done quickly.
    Just like the drawing, a few holes to insert the LEDs or the wires will
    make it easy to mount.
    Yes, a "vector board" is a board full of holes.
    Yes, you are also correct in that the "--" are the "wires" on the vector
    board. Pushing the leads of the LEDs thru the vector board and bending
    them over to solder to the ends of the interconnecting wires can be done
    in no time. How long the interconnecting wires is up to you.

    The next thing to look at is the voltage drop across each LED.
    If you bought the LEDs from R.S., then on the back of the package will
    be the voltage and current rating for that LED.

    Most LEDs are about 2.0 volts each. ( more or less, check the packaging )

    At 12.0 volts, 6 LEDs can be strung together with out damaging them.
    If however your supply goes to 13.6 volts, some of the LEDs may get
    damaged. ( burn out ) Maybe not right away, but one may burnout and then
    the whole string will go out.

    It seems to me that this is a simple wiring problem. This "thing" your
    drilling thru can be used to mount the LED and the interconnecting wires
    can be soldered directly to the legs of the LED. Using some hot melt
    glue to cover the connections will protect the connections.

    No PCB necessary.

    How many LEDs will you need in any single string ?
    As mentioned above, 6 is a good number.

    You many want to insert a voltage regulator before you connect the
    string to the battery. This will help regulate the voltage to the LED so
    any varation will not kill your work.

    R.S. also sells voltage regulators. Look for a LM317.
    This is a 3-Terminal Adjustable Regulator, which means you can control
    the output voltage with a potentiometer.

    Here is a link: http://www.national.com/pf/LM/LM317.html

    Good Luck.
     
  7. Dmitri

    Dmitri Guest

    A PCB is not going to be smooth on both sides unless you are using SMD
    LEDs, and all your soldering as well as parts are on one side of the PCB
    only. The layout of the PCB looks so simple (with SMD parts) that you
    don't even need to etch it, craft knife would be sufficient to cut the
    copper and separate those limited amount of pads you'll need from each
    other. Use gull-wing type SMD LEDs, they are easier to solder than a
    chip-type SMD LEDS. Make your power pads as large as practically possible
    considering the size of the board so they don't easily de-laminate if you
    accidentally pull on the wires hard.
    Good luck!
    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------

    Palmer wrote:







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    Article posted with Cabling-Design.com Newsgroup Archiv
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    no-spam read and post WWW interface to your favorite newsgroup -
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  8. Rich Grise

    Rich Grise Guest

    .
    Only if you are very, very lucky.

    Do not attempt to drive LEDs with a constant-voltage source, without
    a current limiting resistor. In this case, if we take battery voltage
    as a nominal 13.6, then that's 1.6 V you have to drop, at 20 mA is
    1.6/.02 = 80 ohms. So 82 ohms, 1/4 watt will work, but at 14.2V,
    you'll have 27 mA. So go for 20 mA at 14.6V (this is how high the
    voltage gets when it's charging), you want 14.6-12, 2.6/.02= 130R;
    RS has a 100 and a 220, so two 220s in parallel will give you 110R;
    2.6/110=23.6 mA, so you should be OK.
    With no current limit, you are guaranteed to destroy LEDs.

    Also, if the LEDs are going to be in fixed positions relative to your
    holes, just do one board and line them up right. :)

    Good Luck!
    Rich
     
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