Wire size and power supply for control panel LEDs

[Anonymous]

I am newcomer about to embark on wiring up a DDC layout of about 7 x 10 feet. I think that I have the DCC wiring part figured out, but have questions related to the control panels. I plan on using low voltage 20 mA red/green 3-lead LEDs for turnout indication on my control panels (one for each route). These LEDs will be controlled by SPDT accessory switches mounted on my PECO switch machines. Most of the runs from my DC power supply should be 10 feet or less, though a few could be longer where I will have separate control from two panels. What would be the appropiate wire size for the wires running between the panels/power supply and the accessory switches? The charts that I have seen show recommendations for wires routing 1A currents and above, but nothing for the low amperage that these LEDs will use. Can I get by with 22 or 24 AWG for the runs, or do I need something larger? Also, I have seen it recommended to use stranded wire in control panels because the greater flexibility makes it easier to route the wire. Will this be a problem for soldering to the LED leads? I am planning to use terminal blocks at the panel and can change gauges and wire type there if needed. Also, I plan to use a simple DC converter (12V; 500 mA) as the power supply for the LEDs with approprately sized resisters in series. Is there any reason to go with a lower voltage or different type of power supply? Thanks for your help.

[Big_Boy_4005]

Sounds like you have a pretty good plan, and have done your homework well. Your distances are short and your current draw levels are low enough that those sized wires should be fine for that application. Its track feeders that need the larger wires for the most part. Your panel indicator lights are a closed system, there is no connection with the track, so there shouldn't be any danger.

[nfmisso]

Hi Eric;

22 guage gives you approximately 17 ohms per thousand feet, 24 guage you are up to just over 27 ohms per thousand feet, even 30 guage is only around 110 ohms per thousand feet.

Use what you are comfortable with. There is no issue soldering standed wire. I would use 24 guage "speaker wire" it is cheap, and flexible. Here is a source for you:
http://www.allelectronics.com/cgi-bin/category.cgi?category=825700&type=store

[der5997]

You shouldn't have any problem using any of the wire sizes you've got on hand. The current draw for the LEDs is not going to melt the wiers this side of the sun going nova. [:D] On the power supply issue, if you are planning on having some sensors on the layout in the future, you may want to consider buying, or building, a 5 volt power source, and running the pannel LEDs from it. [2c]

[Anonymous]

suggestion: if you use stranded wire, and I recommend it as well, tinning the ends of the wire before you solder will help keep them together when you make your final connections.

[Anonymous]

Thanks for all of your suggestions. [:)] I will go with 24 AWG stranded. Also, I thought about a 5 VDC power supply after seeing the recent articles in MR, though block detection and signalling are not in my immediate plans. If I go the 5 VDC route, what size of power supply should I get? Any recommendations on a source? Thanks.

[nfmisso]

Eric;

Here: http://www.allelectronics.com/matrix/DC_Wall_Transformers.html

Or any old PC's power supply. They put out 5VDC and 12VDC, the four pin connector for the drives has two ground pins, one 12VDC and one 5VDC.

And here are some more.

You will have no trouble with 40 LEDs per 1 Ampere of power supply, I am being very conservative here.