LED Strip (AC / DC Question)

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  #1  
Old 08-21-12, 10:16 AM
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Question LED Strip (AC / DC Question)

Hello everyone,

I'm really happy with my setup in my backyard. My deck has a 300W transformer near it that outputs 12V AC power. I hooked up all my low voltage lights to this with a trenched 10 gauge wire, and now i'm looking to do strip lighting under the remaining dark areas (the railings).

As you probably guessed, everything that I want to buy to strip light is using DC power. What do I do? I have a GFCI receptacle outside that my transformer is hooked up to. I have a free outlet on it, and I suppose I could plug a DC transformer into that but I want to light two areas with strips, one of which is 35 feet away on the other side of the deck!

How do people tackle projects like this? Do I have to trench a whole new set of wire running dc current? I want to somehow use my trenched 10 gauge wire (for the 12v AC low voltage lights). Any thoughts?

Thank you so much and my apologies if anything was a tad ignorant
 

Last edited by ray2047; 08-21-12 at 11:59 AM. Reason: Correct Formatting.
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Old 08-21-12, 10:34 AM
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I believe you can run all of your lights on DC. You would need to get a different transformer though and the bulbs may not last as long (the incandescent bulbs).
 

Last edited by mossman; 08-21-12 at 10:55 AM.
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Old 08-21-12, 10:53 AM
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Actually you can do this by adding a simple full-wave DC bridge rectifier inline with the LED strips. I did this when I switched over some of my Malibu lights to LED. This way you don't lose brightness from the AC bulbs and you don't have to buy a new transformer. It's real simple, you just hook your 12VAC up to the two terminals with the ~, and your LEDs to the terminals marked +/-. No need to put it into an enclosure because they are potted and the voltage is low. Just screw it to the wall/deck post/joist where the wires come out of the ground (make sure the cables are fastened too so they cant get yanked), and use insulated spade terminals to prevent shorts.

They cost about $5.

NTE Electronics, Inc. - NTE5322 - Semiconductors - Diodes - Allied Electronics
 
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Old 08-21-12, 10:57 AM
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JerseyMatt, according to the datasheet, the output voltage will be about a volt less (11V). Will this affect the LED circuitry? Doesn't seem like enough difference to matter, but figured I would mention it.
 
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Old 08-21-12, 10:59 AM
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Should I just buy a few of these? Low Voltage LED Under Railing Deck Lights and Under Step Lights - Moonlight Decks™

it claims to run off AC.. are there more products like this?
 
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Old 08-21-12, 11:01 AM
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Compare prices and then make your decision. Those are $80-$170 a piece. Seems rather expensive for a strip of LEDs.
 
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Old 08-21-12, 11:03 AM
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I agree.. Wow @ that rectifier. So just to rephase, I literally can cut my 10 gauge wire, and then splice up to the ~ terminals. Then just take the LED and hook up to the +/- terminals, and i'm done?

So conceivably I can do this multiple times (2-3 let's say I need) at any point in the wire?
 
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Old 08-21-12, 11:05 AM
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Yes...very simple. Thanks JerseyMatt, I didn't realize such a part existed in this type of sealed package.
 
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Old 08-21-12, 11:14 AM
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so my output is 12V AC and the light strips I was looking at were something like this: LED strip light warm white Colorbright Series, 600 LEDs per reel

Sorry to ask/bug you but does that product spec (just as an example let's say) coincide properly with the rectifier? I can just pull apart the leads from the led strip and connect to the +/- ?

btw how do I know what is +/- on the led strip? i know for the low voltage cable it's notched
 
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Old 08-21-12, 11:52 AM
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I'm assuming the installation instructions will tell you what the polarity is. It will only work on way so if they don't come on, just flip the connections (you won't hurt anything). By the way, these appear to be for indoor use only.
 
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Old 08-21-12, 12:07 PM
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Thank you I just noticed that. They do have some outdoor ones but this particular reel seems a bit pricey (perhaps they all are). At any rate I need to do some looking now, unless you have done something similar that you would recommend?

Do you suppose these are dimmable?
 
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Old 08-21-12, 12:40 PM
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I prefer the incandescent type landscape lights because of the color temperature. The LEDs are too harsh in my opinion. I'm sure there are comparable ones, but I honestly haven't looked. Do you HAVE to go with LEDs? If you're mixing incandescent and LEDs, you are likely going to have a color difference, which wouldn't be desirable.
 

Last edited by mossman; 08-21-12 at 12:56 PM.
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Old 08-21-12, 02:13 PM
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Wow y'all had a whole discussion while I wasn't looking!

1. LEDs wired for 12v will tolerate undervoltage down to about 9v before they start dimming out. You'll have no issue with the 11v.

2. I explained in a bit more detail how you should make the connection in a reply to your PM. You don't want to 'wrap' the wires around those terminals, you need to use crimp-on spade terminals for a safe, reliable connection. That pic is larger than life.. In reality, it's only about the size of a quarter, and the terminals are only 0.250" wide.

3. Yes, you can absolutely do this as many times as you want. That rectifier will support many thousand LEDs in strip form, or many hundred in 'plug-in' form, so if you want to have just one DC circuit that will be just fine, or you could have several DC circuits fed at any point from the AC circuit. You are only limited by the output capability of your transformer.

A regular Malibu tier light bulb is 4w. An LED replacement is 0.3w. So it takes 13 LEDs to equal the power draw of a single incandescent. In the spotlights, the MR16 halogen bulb is 10 or 20W. The LED replacement is 1 or 3W. So you can put many many more LEDs on your transformer than you can with incandescents. Those strips are 3w per foot, so just multiply that by how many feet total and see if you have enough extra capacity on your transformer.

I would also urge you to shop around for those lights. If you look at that listing, that is $9 per FOOT. There are other places that carry them for $40-50 per 16' roll.

EDIT: Here's a site that's got them for $47 for the roll, and they are outdoor rated with the adhesive back (I'd still use glue or clips though).

Warm White 12VDC Single-Chip Flexible LED Strip, LED Strip


They use a clip-on power connector with red/black leads so it looks real easy.


8MM SMD3528 Strip to Strip with wire LED connector, LED Strip

And they even have a dimmer control (I doubt it's for outdoor use though unless you put it in a protective box)

LED Rotatory Dimmer 12V 8A, LED Strip

4. If you use the Warm White LEDs, you'll never be able to tell the difference from an incandescent. They look exactly the same. The COOL white ones have the harsh blueish white light, and those are the ones you want to avoid for your accents.
 
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Old 08-21-12, 08:19 PM
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wow thank you for finding this for me!

LED Rotatory Dimmer 12V 8A, LED Strip this is something I was thinking about as a matter of fact!

I need to run 4 led strips in different areas along the same wire - they're all roughly 5 feet away from each other, but they're underneath different parts of the railing (the railing makes a few turns in each direction).

What would be a smart way to make it so all of them would dim from one switch? I could envision a connector extending one strip but the thing is they branch out from two different directions?
 
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Old 08-21-12, 10:29 PM
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The best way to run the wire really depends on how the railing is laid out and what it's made of. If it's wood, you would probably be best off stapling very thin cable (18-20ga) for each strip to the least conspicuous side of a vertical picket, cover it with a piece of hollowed out half-round molding for protection, and make your junction somewhere under the deck. If it's vinyl, it's hollow and you can usually figure out how to take it apart and run the cables inside. I would suggest you don't run them 'chained' together, as if one ribbon gets damaged, it would make anything after it go out.

As I said, I doubt the dimmer is rated for outdoor use, so basically you'd have to mount it inside a box with a cover to protect it from moisture.
 
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Old 08-22-12, 09:14 AM
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Great. So in summary, if I may:

----------------------------------------------------------------------------------------------------
1) I would first cut my 10 gauge wire and put both neutrals together into a weatherproof/silicon filled wire connector, and both hots into their own as well. Then i'd take some 12 gauge wire and slip that in the wire connector to leave a pigtail sticking out (2 pigtails, 1 for each connector). I'll take the pigtails from both and connect them to their own spade terminals.


2) Each spade terminal would plug into the ~ leads on the rectifier.


3) The remaining 2 leads on the rectifier (+ and -) would get their own spades as well, and i'd run 12 gauge wire (or smaller) out from the +/-'s to a dimmer switch: LED Rotatory Dimmer 12V 8A, LED Strip
The dimmer is for indoor use only, so i'll have to house it in something.


4) Now i'll mount my led strips under the deck railings, and i'll run 18-20 gauge wire from all the strips (i'll have roughly 5 separate wires) into one single wire (i'll join them all together). I'll then take this single wire and connect it to the +/- output of the dimmer switch.

5) I should now be able to dim all 5 LED strips from the dimmer!




Any thoughts?
 
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