What gauge wire for LED lighting?

Model Railroader Electronics and DCC
21

Thanks Randy

I have another question: When I am calculating the length of the run do I include the length of the LED strips themselves or just the hook up wire?

Dave

22

Another question:

Since I will be running 5 amp leads off of the power supply, should I have circuit breakers in each line, and if so, can you recommend which breakers I should be using?

Thanks

Dave

23

Something like this would work:

http://www.ebay.com/itm/5-Amp-Panel-Mount-Push-Button-Circuit-Breaker-for-Boats-Push-to-Reset-Design-/120995129372

They’re 12V DC breakers for boats. There are automotive ones too. Some are in the form factor of the blade fuses for cars, which means you would also need some sort of fuse holder or block - there are high current 12V distribution blocks with fuse holders meant for adding lots of heavy duty 12V accessories to a car or truck, you could use one of those panels to break the big power supply into multiple 5 amp circuits.

Something like this:

http://www.amazon.com/Blue-Sea-Systems-Blade-Block/dp/B000THQ0CQ/ref=pd_sim_200_3?ie=UTF8&dpID=51%2B5nXsWtYL&dpSrc=sims&preST=_AC_UL160_SR123%2C160_&refRID=0TXR93P5DSV6JV3VE8R1

For your wire length, don’t add in the LED strip, just the length of wire from the power supply to the terminals on the end of the LED strip.

–Randy

24

If you haven’t purchased your LED strips yet I would suggest you consider 2835SMD strips. I went through this decision process recently and the 2835 LEDs put out a lot more lumens/watt than the other LED SMD options currently. I wanted to keep all my layout lighting LED power supplies in a central location which lead to some fairly long runs for the layout lighting LED 12V power bus. I opted for 12GA bus wire because I have a couple runs that in theory are pulling about 10-12AMPS.

From my post on another message thread:

[quote]

I chose to go with 2835 LEDs vs 5050 vs 3528 vs 5630 because they are significantly more efficient in terms of Lumens/Watt and they have a better heat sink design so they run cooler. I tested various 5m LED strips and found the 2835 strips use about 1.8 amps at 12V.

SMD2835 have efficiency rating of 130 versus 90 for the SMD5050: https://en.wikipedia.org/wiki/SMD_LED_Module

http://olympianled.com/led-smd-5050-vs-2835-vs-3528/

LED SMD 5050 VS 2835 VS 3528

So what do these numbers mean? Is one better than the other? Well, the numbers actually represent the package size.

SMD Type Dimensions Watt
SMD5050 5.0mm x 5.0mm 0.24
SMD 2835 2.8mm x 3.5mm 0.15
SMD3528 3.5mm x 2.8mm 0.08

SMD stands for Surface Mount Device. SMD 2835 is the newest SMD configuration and offers the best cost / performance. It is significantly smaller than the SMD5050 and has better heat dissipation.

Advantages of SMD 2835 vs 3

25

Hi Onewolf:

Unfortunately, I have just ordered 10 x 5m strips of 5630 natural white LEDs - 60 LEDs/m and two 36 amp x 12v power supplies. Everything is in shipment as we speak. I wish I had known about the 2835 strips before that.

Fortunately, there is always eBay so if I want to go with the 2835s I can always get rid of the other stuff. I already have power supplies that would be suitable for the 2835 strips.

Dave

EDIT:

Can you tell me where you got your 2835 LED strips?

26

Dave,

A handy chart to have around…just scroll down to it…:

http://www.powerstream.com/Wire_Size.htm

12 gauge stranded, should be fine.

Take Care! [:D]

Frank

27

I’m going to question this with a logic query …

Why would it be necessary to use such a heavy gauge wire when the CIRCUIT TRACES themselves carry the full current, and they are considerbly smaller than 12 gauge wire ?

Not that I’m saying anything like 22 gauge wire would be recommended, but 12 gauge sounds a bit like overkill.

Haven’t we gone over this in another thread ? …

Mark.

28

According to handy chart referenced in above post, go no smaller than 14AWG for those 5 amps, so, based on that, 12AWG is not that far off.

With 10 strips, per other thread, I would totally recommend “overkill”, if only for safety reasons. 50 amps is quite a bit of power to be messing around with. Hope those strips all get their own supply line. If they don’t, even 12AWG is not enough, per referenced chart. If it is all one line, then now we are talking 3-4AWG instead… So, I only hope those 10 are broken up.

29

Can one of you electrical guys explain this chart to me? They want 14ga wire for 5 amps, but house wiring spec is 14ga for 15 amps and 12ga for 20 amps. Why the difference?

Also, for the OP’s question, isn’t the length of the wire important?

30

Can someone explain how the paper-thin circuit traces can carry 5 amps the length of the 16 foot strip, yet you have to connect it with 16 feet (for example) of wire 20 times plus that size to the power supply ?

Mark.

31

I think what has been missing above is the fact we are talking about 12 volts, not 110/120 volts. This chart shows considerbly smaller values for 12 volt applications …

Mark.

32

To fine tune the lower current ratings, according to this chart, at 12 volts, you can push 5 amps through 22 gauge wire for almost 3 feet …

Mark.

33

I don;t know about your LED strips but the ones I have, that is no paper thin trace running the length of the reel, it’s a pretty darn wide trace, actually. And relatively thick compared to a typical low voltage low power electronic PC board.

There are two different things here - one is the current carrying capacity of a given size wire, which is the larger of the two numbers and represents how much current you can run through the wire without it heating up excessive. Then there is the voltage drop based on the wire resistence per foot and thus also directly proportional to the current. For a reasonable voltage drop of less than 1 volt, and with only 12V to start with, 1/2V is more reasonable, the amount of current that you can have will be much less than that size wire’s absolute maximum current capacity.

Per the chart - #18 wire is good for 5 amps at 25 feet. But draw 5 amps through 25 feet #18 wire and you will have almost a full volt less at the end. Not sure how they laid out that chart, if they mean 25 total feet for the circuit or 25 feet absolute distance. If they mean 25 feet for the circuit, that’s only a distance of 12.5 feet. If they mean 25 feet actual distance, a complete circuit would comprise 50 total feet of wire, in which case the voltage drop is almost TWO full volts. The same length of #12 wire would drop .2 or .4 volt at 5 amps, depending on if they mean 25 total or 25 distance, with 50 feet of wire total. Significantly less voltage drop.

–Randy

&nb

34

Well, instead of guessing through online charts, I checked out a few online professional sites for LED ribbon lighting …

Their recommendation for hook-up wire to be soldered to the strips is to use between 18 and 22 gauge stranded wire.

Don’t shoot the messenger …

Mark.

35

Yes but for how long a wire run? The power supply and controller that came with the reel of LEDs I bought is only like #22 wire, but it’s also only about 3 feet total.

–Randy

36

That would make sense based on the second chart I posted …

Mark.

37

Because I can guarantee that when I install LED strips on my layout, if I ever get to the point of building it, the wire runs from the power supplies to the strips will be #12 wire, like I use for my DCC bus, because they will be a lot longer than 3-5 feet. Like DCC boosters, the LED power supplies will be distributed along the layout to keep the wiring as short as possible. If sized for at least 2 strands, ideally it will be located in the center of the two strands, in order to get the most coverage possible. Assuming 5 meter reels - 5 meters in from one end is a power supply, then the second 5 meter reel, then another 5 meter real, thent he second power supply, etc.

----------PS----------<>----------PS-----------<>----------PS---------<

Further complicated by two levels of benchwork and more than one strnad of LEDs, and some home bre controllers. In addition to white LEDs, I want a string of RGB ones to do dawn, dusk, and night effects. The ones I have are severely limited in the colors they display but until I dissect the controller I don’t know if the limitation is in the way the controller was designed or in the IR remote that came with it which is the only way to control it. I need more steps per color to make the transistions smoother, plus I need to drive multiple spools. Not a terribly complex circuit, but for the number I need, it will have to work something like a DCC command station and boosters, where the main controller outputs a low level signal to multiple controllers, each running a reel or two of the LEDs so i don;t have to use massive heatsinks and fans to cool the controller. Multiple smaller, distributed controllers all keyed off one master signal. Should be fun to design and build.

–Randy

38

Hi Mark:

Yes, the subject was broached in another thread, but what I am asking is: is there any technical difference between speaker wire and other wire which would prevent its use.

As to the need for 12 gauge wire, there were several opinions offered but the PowerStream chart that Frank refers to seems to suggest that a continuous 5 amp load requires the heavy wire. I understand the apparent conflict between the trace wires used in the LED strips and the power supply wires but I want to get this right.

Dave

39

Hi Frank.

Thanks. I already had the chart but maybe I’m not understanding it.

Dave

40

I guess I should have added this question to the thread on wire gauge. I’ll send Mr. Otte a note asking if he can combine the two.

There appears to be some conflicting information between the three charts referenced above. Based on a 20 foot run with 5 amps continuous draw @ 12 volts:

  • The calculator in Frank’s PowerStream chart suggests a minimum of 14 ga. to keep the voltage drop to about .5 volts.

  • The first calculator that Mark shows suggests that 18 ga is sufficient, but it doesn’t reference voltage drop.

  • The second chart that Mark references suggests that 12 ga is required although you might get away with 14 ga if the actual run is only 18.4 ft.

Based on two out of three, my conclusion is that, in order to play it safe. I should work with 12 ga. wire. Many of the runs will be shorter than 20 ft. but I choose to use the same wire throughout.

As far as the original question about ‘speaker wire’, nobody has said it can’t be used. I told you it was probably a dumb question![swg]

Thanks again

Dave