Another DIY poster/marquee light-box - Page 7

Actually it does and explains the results I got vs what you mentioned

So in essence you have 1 connection point where your "home run" line and 2 LED strips meet ... then the same for the next group.

Thus 2 home run lines back to the power connector.

Right?

Greg

Not quite. You may still be wiring them wrong. Each strip has two leads at each end, a positive and a negative. Each individual LED is wired across the two busses.

The "home run" wiring suggests that EACH strip be wired to the power supply at each end. Thus if you had two strips, you would have a total of 4 positive and 4 negative wires running to the strips. They would be wired as a positive lead to the positive bus connection at each end of each strip, and a negative connection to each end of each strip.

If you use a fairly heavy wire (say 14 ga) you can run a single wire point to point along the run instead of running multiple wires all the way back to the power connector. The point is that cuzed and others have observed a voltage drop along the led strip busses, which indicates that the strip cannot handle the current of an entire strip. Adding the "home run" at the other end effectively shortens the run and solves the voltage drop issue.

Hopefully that makes sense. I can probably draw a picture tonight unless someone beats me to it.

Yes and yes.

GCS, what you have iterated back sounds correct. Remember to watch the ends of the strips because with this method you have to make sure that positive and negative ends match (they actually switch between ends).

Jayn_J,
I agree with what you are saying, however we are not seeing a visual drop across one 5m strip, but seeing it in the second one when they are connected or soldered together in series. The problem is not the voltage/power from the power supply, its the voltage drop being observed across the 2 strips of LEDs. One set of wires should provide more than enough power to power all 4 strips, but its the loss of voltage across each LED that prevents this (and why you see the 2nd, 3rd, and 4th strip get dimmer). By soldering two strips together with a lead we essentially put the 2 strips in parallel.

Hopefully this helps make everything clear.

Here is my current wiring set up.

Please note that where the wires meet they are wire nutted together and no bare ware contacts the other (ie crossed wires)



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DaDeuce method if I have it right that is



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This is exactly what I did, but instead of running my home runs to one end of the strip, I actually solder my wires to the same spot that I solder the two stripes together. I'm posting from my phone, but if this is still confusing I can draw a picture when I get home.

My current setup is the first drawing.

When I tried your suggestion we ended up with a darker second strand. Made no sense to me either but that is what happened

Greg

Not the case Craig. Each strip is like this:


|-LED-|
|-LED-|
|-LED-|
| ... |

The LED is across the two bus lines, so no matter how they are wired, all the LEDs are in parallel. What you are seeing when you wire the strips in series is the resistance of the bus lines themselves.

Ok here's a quick sketch of the way I am wired:



So the key here is that the strips are soldered together end to end. (Make sure you put the correct ends together as you might not put positive to positive and negative to negative). One they are soldered together I come back in and solder my wires to the same joint I just solder the ends together one. So at one joint I have Strip #1, Strip #2, and my wires all soldered together (the leads would be independent of course).

Does this clear it up?

After months of procrastinating I used up the remains of my pile of Walnut and made three lighted movie poster boxes for my theater entrance.

Craig, thanks very much for this thread, it made progress painless. I just posted these in my build thread (see sig) together with some construction pics but thought I'd share here too.



This is the first view that greets me when I go down to watch a movie



Close up of the frame profile:



Specifications:

• Solid walnut, finished in shellac and satin polyurethane.
• 2 3/4" thick
• 3x15' LED strips in each box, wired in strips to minimize resistance drop
• 5A power supply integrated inside box direct wired into wall
• 3/16" frosted plexiglass creating surface to mount spotlight front loading frames

Hope this is useful

Cheers!

Thanks! I wanted a border around the spotlight frames and so built it like an elaborate picture frame. The white board the LED's were affixed to was inserted from the rear side, tacked in place with hot glue and then reinforced and glued in the corners to allow me to screw through to mount to the wall.


I used this 5A waterproof LED power supply. It was shipped from China and was the cheapest listing by far. I have not issues with heat running 3x15' strips in each box. In fact it barely gets warm. I said 4 in my original post -- I'll update. This is plenty bright enough for my use in my darkened entrance. The only quirk is that it takes a couple of seconds to turn on when cold.


That would be Home Depot . Here is a link to the actual product. The product is called "OPTIX 48 in. x 96 in. x .118 in. Frosted Acrylic Sheet". I persuaded my local store to order for me for in-store pickup and so avoided any additional shipping charges. It cuts very easily on the table saw.


Yes I cut up the strip to avoid wasting any light and to ensure even coverage. I only used 3 15' strips per box and so I think the spacing was closer to 1.5" -- basically I got 5 strips per roll, so 15 across the width of the box. In any case with the box depth I choose (2" plus the additional 3/4" trim on the front) and the Optix frosted plexiglass I cannot make out the individual strands. I soldered them all up in groups of three. Here is an additional construction pic (there are one or two more in my construction thread) -- you can also see the power supply mounting.

Moggie,

Good work. I'll admit that I hadn't even thought about clipping the stripes and soldering the ends together like that. Seems that while it would add a few more minutes of soldering, provides a better effect and makes running the strips easier. I definitely think I will use this method if I ever build anymore.

Yeah, I was a little worried with all you guys saying you needed 4x15' strips but honestly my 3 strips is fine. I am using proper double sided posters.

I wired it the way I did to maximize the LED distribution over the poster area and ensure I didn't get any brightness drop due to accumulated resistance. The extra soldering didn't really take much time, maybe 30 mins extra per box.

Hey cuzed2 - what is the total width of this box, including your wood frame?

Bump this up..... GCS you have any luck fixing your frames?

Moggie (or anyone who can lend a hand),

I'm getting ready to get into my box now that I have most of my materials. I'm not much of an electrician.. at all. Is this how you wired your box? Do I have it right?

The lights look cool all lit up at night while lying on the ground. I kind of want to run them throughout the house to see how it looks as a permanent lighting solution.

Hi Adam,

Your wiring diagram (a parallel/series/parallel combination) will work just fine although you can move the short jumper connections all to the lower end and thus wire every strip in parallel if you like (this configuration will completely eliminate and possibility of voltage drop between strips. That said, all you are trying to do is avoid a very long series connection (daisy chaining) of strips -- such a configuration might result in a voltage drop with strips at the end of the chain slightly dimmer than at the start. Basic ohms law, V=IR. The manufacturer obviously believes that 15' is the maximum length when using unbroken copper connectors on the strip itself. Since you are cutting the strip up I'd keep the lengths shorter...

Cheers.

Thanks for the advice. I want to be sure I understand you right and I don't do anything wrong. Sorry for my lack of wiring knowledge.

This better? Looking forward to building this.

Yep. That's the way to do it.

Where did you get the rolls? Might have missed it. Boxes are coming along nicely....

Bud

I think he's used these:
http://www.ebay.com/itm/220736520180?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I have them in my watch list as I don't know if I'm going to go the LED route or stick with the fluorescent route like I did before.