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Multiple LEDs to a single PC power supply

Discussion in 'Power Electronics' started by Vampiel, Jun 7, 2013.

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  1. Vampiel

    Vampiel

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    Jun 7, 2013
    Hello,

    I am trying to hook up multiple LED's to a PC power supply. I have all of the resistors pre-wired into the LED's already and basically just need to get power to all of them. There's around 15-20 of them and they are going to be powered by 12v DC coming from the PC power supply.

    Initially I was going to use a breadboard but the solderless ones aren't for a permanent connection. I was thinking of using something like a barrier strip where each side is connected all the way down instead of each one separated. This way I wouldn't need to solder anything and could just screw each connection down, then screw in the power supply into just one connection on each side of the strip.

    Would this work and is there such a thing?

    Thanks for any help!
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Am I right to assume that you want these LEDs to illuminate the different parts of a computer, with a transparent side panel?

    It depends on how you want to support the LEDs.

    A common construction method is stripboard (also called veroboard) - Google it, and you'll see what it looks like. LEDs and their current-limiting resistors are soldered through the holes and onto the tracks, and the board can be mounted with screws or whatever you want. You do need to insulate the tracks so they can't touch on anything else metallic.

    Another approach would be to use heat-shrink insulation and thin twin insulated wire, and build up individual modular LEDs that can be mounted independently. You could put a two-pin Berg strip connector (like a jumper shunt, but with separate connections to the two halves) on each LED, then make a "distribution board" using stripboard and jumper pin strips, to power the LEDs. Similar to how front panel LEDs connect to a PC motherboard.

    The simplest way to connect the LEDs would be to have a separate current limiting resistor for each one; that way, each one can be independently plugged into a 12V supply. You could save a bit of power by connecting the LEDs in series strings. Make sure you understand how to calculate the resistor values. There used to be a good article on this site for that, but it seems to have disappeared. There is a web-based current limiting resistor calculator available; Google it.

    If you can tell us more about your application, we may be able to make more specific suggestions.
     
  3. Vampiel

    Vampiel

    4
    0
    Jun 7, 2013
    Hi thanks for the reply.

    I have the LED's mounted on a piece of acrylic that will go onto the side of the PC. I was hoping to avoid soldering any connections just due to the time it takes since I will be making more of them. I ended up finding a solution of using the female connectors that go inside of the old type of PC internal power connectors.

    I just pulled the wire through, then wrapped it around at the end and this seemed to work. I wish they actually made a terminal strip that would work for this.... but I only found the ones that connect 1 to 1 instead of just two strips like the power of a breadboard is setup.

    I've attached a few pics for clarification.

    https://sphotos-b.xx.fbcdn.net/hphotos-prn2/980587_624736064205501_1088321356_o.jpg
    https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-prn1/976041_623646487647792_1940386870_o.jpg

    Oh and yes, the resistors are already built into each individual LED...
     
    Last edited: Jun 10, 2013
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    LOL! Those "connector strips" aren't connector strips. That's the way the little terminal inserts are shipped - all attached along a metal strip. You're supposed to cut them off individually when you insert them into the plastic connector shell.

    What you've done is alright of course, provided that you insulate them properly. You could just as well have twisted all the wires together though.

    You could do a more compact and tidy job using stripboard and dual Berg connectors (these are also called Molex connectors, but Molex make a lot of different types of connectors, including the old-style hard drive power connectors, so I called them Berg connectors to avoid confusion). There are many other options as well, such as insulation displacement type connectors where you just push the wire in between two bits of metal and they cut through the insulation. A similar method used to be used for telephone wiring; they were called "hedgehogs" I think.

    Anyway, if you're happy with what you've done, that's what matters :)
     
  5. Vampiel

    Vampiel

    4
    0
    Jun 7, 2013
    Yea I knew they were meant to be cut up, which is why I thought it was so strange they didn't have something like this that was meant to be used the way I did without having to solder connections.

    I am happy with the way it is, except the fact that it's a bit messy.... but it's dirt cheap and works. I didn't want to just twist them all together in case one of the LED's goes out so it would be easier to replace one piece instead of having to undue everything, plus I wanted it to be a little more organized.

    Is this the berg connector you're talking about?

    http://www.tekscan.com/store/flexiforce-sensors/male-berg-connector.html
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    No, that's a different kind of Berg connector. I guess Berg make a lot of different types too :)

    What I'm suggesting is a dual row of pins, of the type that's used on PC motherboards for the connections to the front panel components (LEDs, pushbuttons, speaker etc). These are more generally called "0.1-inch pin strips". They have a 0.1 inch pitch and stand about 10 mm high. You can get the pin headers in single and dual strips. They're also used for option selection jumpers on motherboards (at least, up until about ten years ago).

    It seems that Molex call these parts "C-Grid" or "C-Grid III". These are available in various lengths. There's a 16-pin one (two rows of 8 pins) at http://www.digikey.com/product-detail/en/0901310126/WM8124-ND/760838

    Instead of putting a "jumper shunt" on two adjacent pins, you put a two-pin socket onto each pair of pins. The socket has two little metal spring contacts in it, and you connect the LED wires to those.

    Then you get a long thin piece of stripboard, and solder the pin strip long-ways, so all the pins along each side are connected together in a long line.

    While searching I also found this: http://www.radioshack.com/product/index.jsp?productId=12825865 I'm not sure whether it's suitable or not; you'll need to confirm.
     
  7. Vampiel

    Vampiel

    4
    0
    Jun 7, 2013
    Ok I see what you are saying. I will give that a shot, and if it's not to much more work I may end up doing that instead. It would be cleaner than what I have. I would have to get a larger one than the one you linked at radio shack but it looks like they have more.

    Thanks again for your help!
     
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