Layout Lighting and DCC

[conrail98]

He also added what he called "glue spots" to the backs to give them more hold. I have the name of it written down somewhere so I'll have to go search for it. He said he got them at the local craft store. He also had some gigantic power supply there that we all kind of raised an eyebrow at. I can say this much, it was the most talked about work-in-progress clinic afterwards,

Phil

[C855B]

While this discussion is going on, what types of fixtures are available for LED strips?  I was envisioning ripping plastic pipe and covering the inside with aluminum reflective tape.  Is there a better idea?  There must be 

There are. And as you will see, OMG are they pricey. This was one of the price/performance issues that steered me away from strips and back towards theater-style lighting. (Which, BTW, my order of umpteen RGB+W+A+UV PAR cans arrives Friday. I'm not ready and won't be for a couple of months, but at least they're on site.)

[Scottl]

Thanks, you are not kidding.  I'm still searching for a cost effective solution.  I only have 5m of lights, but that would still be a lot.

[C855B]

... He also had some gigantic power supply there that we all kind of raised an eyebrow at. ...

Those with exposure to ham radio and professional communications know about these. I've installed a couple of the 60 Amp versions myself. Yes, you can almost weld with this stuff, but I wouldn't recommend it. Fooling with high-amp supplies is the reason I fell out of the habit of wearing my wedding ring. A fellow technician once accidentally bridged his ring between the unfused 12V master bus and ground - it was nearly instantly red hot. He was most fortunate in not losing the finger.

[peteski]

A fellow technician once accidentally bridged his ring between the unfused 12V master bus and ground - it was nearly instantly red hot. He was most fortunate in not losing the finger.

And yet, you can stick your tongue directly across those buss wires ans all you will get is a strong tickle.   Ohm's Law baby! 

[daniel_leavitt2000]

Mike, that site is awesome! thanks for the link. That solves a lot of "Where to get..." questions for me.

[C855B]

My pleasure. They've been my go-to for a bunch of years, since way back when they had little more than component LEDs. They grew right along with the LED market.

[conrail98]

This just popped up over on the MRH site. Kinda shows what I was describing with the valence,

Phil

[daniel_leavitt2000]

Oh a computer power supply! 280 watts, several lines out. Just perfect for lighting!

[Scottl]

The 12V outputs may be limited, but these are useful supplies in some cases.

[C855B]

The 12V outputs may be limited, but these are useful supplies in some cases.

Yes, you'll have to double-check the power breakdowns. Older designs are biased toward most of the wattage on the 5V lines.

OTOH, I found this cheap 550W monster. 43 amps on four +12V lines. More power to you... literally.

[daniel_leavitt2000]

Ok I found 12v 300 watt power supplies on eBay for about $25.

So now a little math:
Double density LEDs (golden white and daylight) will require 1.25W per foot.
Single density lights (amber and blue) will require .625W per foot.

Layout areas 15' + 30' + 30' + 10' + 10' and a 10' island = 105' per color

Golden white: 131.25W/12V = 10.9A (Yikes!)
Daylight: 131.25W/12V = 10.9A
Amber: 71W/12V = 5.9A
Blue: 71W/12V = 5.9A

This would mean I can use a 400W power supply (I rounded up on the math), or two 200W supplies that each feed a white and a color.

So wiring... According to this chart, I would need to use 11AWG wiring for the white LED strips and 14AWG for the colors. That is pretty thick.

http://www.cablesandconnectors.com/wiregauge.html

Does this sound right to everyone?

[peteski]

How about dividing the lighting into something similar to DCC power districts on large layouts. Basucally split the lighting into smaller areas, each with its own supply?  That would also allow for more control of the lights in various areas of the layout.

[daniel_leavitt2000]

I was thinking of that, but I want to control the lighting evenly.

I guess my question is more about the wire gage... isn't household wire 14 gauge? And that's rated for something like 600 volts at 15 amps. Why does this wire need to be so robust for a lower voltage installation.

[peteski]

I was thinking of that, but I want to control the lighting evenly.

I guess my question is more about the wire gage... isn't household wire 14 gauge? And that's rated for something like 600 volts at 15 amps. Why does this wire need to be so robust for a lower voltage installation.

House wiring (ROMEX cable) is usually 14 or 12 AWG  14 is for 15A circuits and 12 AWG is for 20A circuits.   The heaviness of the gauge has nothing to to with voltage (120V or 12V) but it is all about the current carrying capacity.  It is all about voltage drop and heating of the wire (due to its resistance) under load.

Here is a handy charto of the current carrying capacity http://www.powerstream.com/Wire_Size.htm and more detailed info along with the chart http://en.wikipedia.org/wiki/American_wire_gauge

The charts also provide the resistance of the wire so you can figure out the voltage drop in your specific application.