I have a 13.8 20 amp power supply on hand, Would it work to power street lights, house and building lights, that kind of stuff on a HO layout?
More than likely! 20A is a decent amount of load capacity. 13.8V will probably droop closer to 12V as you load the Power Supply down, but thats still a good voltage to work with.
A few things to take into consideration:
-LEDs usually require 1.5V-2.5V. They will need a resistor in series with them to prevent the 12-13.8V from driving too much current through them.
-The same can be said about bulbs, but the allowable Voltage range of bulbs is usually a bit more varied. (aka, there are 1.5v bulbs, 5V bulbs, 6V bulbs, 12V bulbs, 14V bulbs, etc)
-Calculate to have about 75%-85% of the rated current through the bulb/LED. Lowering the operating current will prolong the life of the device while only lowering the brightness slightly (if even noticeable)
Check out the link in my sig for a quickie “For Dummies” tutorial of Basic Electricity
Dave,
Can’t get the site to load for “Basic elect…”
Would love to review.
pjjkg
try this: link
Heh, my bad. I worked the site into xhtml strict 1.0 valid and forgot to update the link. 
Its fixed now!
Thanks 7793 and Dave.
Look forward to reading in depth your tutorial.
doc steve