LED light strip - wiring multiple sections

Discussion in 'The Projects Forum' started by knightfork, Sep 11, 2013.

  1. knightfork

    Thread Starter New Member

    Sep 11, 2013
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    I'm planning on buying 12VDC SMD3528 LED strip lights, such as these: Amazon.com: HitLights Cool White Double Density 600 LEDs Flexible Light Strip, 3528 Type SMD, 5 Meter or 16.4 Ft, 12 Volt, 48 Watt: Home Improvement

    This will be used to light a cabinet. The entire LED strip is 48W, so 4A on 12VDC. I want to use the entire 16ft, but partition it into 4 pieces: 3x1ft sections and 1x13ft section. The shorter sections would be to light up individual shelves, while the large section would go around the inside of the door frame.

    Can I wire these like so:
    [​IMG]

    Hopefully the above diagram makes sense. Basically, I'd like to split the power lead coming out of the switch into 4 leads and drive 4 LED strips. Would this plan work?

    In terms of splitting the wires, I'm thinking I'll solder some wire to the coming off the switch. What type of wire is appropriate for this? 18 gauge? 22 gauge? Should it be copper or is copper clad aluminum suitable?

    Also, should I solder all 3 additional leads to the first wire in the same spot, or solder each of them to the main wire where I need them to branch off? I.e.:

    [​IMG]
     
  2. wayneh

    Expert

    Sep 9, 2010
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    What is the function of the "switch"? Is it really switching between strips or is it a junction box?

    As I understand it, you can properly cut this into sections, any one of which still needs 12V. This means you can wire strips just like you wire a house - every strip is connected in parallel to your 12v "mains". You can use either a bus topology or a star. I suppose a house is wired in a star, with the center at your breaker box.
     
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  3. knightfork

    Thread Starter New Member

    Sep 11, 2013
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    The switch would turn the lights on when the door is opened, and turn them off when the door is closed.

    As I understand it, the typical magnet switch wouldn't be suitable because they are more for signaling, while the switch in my proposed circuit would have 4A passing through it.

    A refrigerator switch (like this one) should work even on DC, correct?

    My first diagram is essentially all LED strips wired in parallel (in star topology), correct? Would that work even though the strips are of unequal current draws?

    The second diagram seems like a combination of parallel and serial circuits. Would this setup work? Or am I better off going with a simple parallel circuit setup?

    What type/gauge wire should I use for this application?

    Thanks!
     
  4. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,292
    1,255
    I would use the first diagram just because I think it will be neater. Hooking wires to the LED strip might be tough.

    22awg is ok.
     
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  5. knightfork

    Thread Starter New Member

    Sep 11, 2013
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    That's a good point. If I went with the second diagram, I'd have to cut the strip (Strip1 in the diagram) in a few places and make a lot of connections that could be avoided by wiring as per the first diagram. I'd save some wire length of minimal cost at the expense of a lot more work.

    In the first diagram, I show 4 leads coming off the switch. The refrigerator switch I'm thinking of using looks like this:

    [​IMG]

    My understanding of these switches is you place it on the negative line. So I'd have the negative line coming out of the DC power supply and solder that onto one of the switch prongs. Would I then solder all 4 negative leads for the LED strips to the other switch prong? Is there a more elegant way of making this connection?

    Does this fit the bill? 20ga 25' Red/Black Hookup Wire 12V DC

    It's 20ga, but cheaper than the 22ga wire I could find because of the free shipping, plus I don't need to buy wire in bulk for this and other upcoming small DIY projects.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,154
    3,060
    That wire should be fine. The ad says it's copper (which is good, easy to solder).

    If you want all the lights to come on together, then yes, all the negative leads come back to the switch. You might want a terminal block or some other way to bring them all together, so that only a single lead goes to the switch. It would be nice to have a way to isolate a string from the others, if you ever need to work on them in the future, make replacements and so on.
     
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