# How to run 12v lights through 110v wired house?

by ulhbuilder
Tags: 110v, house, lights, wired
 Sci Advisor P: 1,724 Welcome to PhysicsForums! Unfortunately, most LED bulbs still aren't terribly bright, although you can buy CFLs and full out fluorescent tubes that run at 12V--you find a lot of these in campers and RVs, as well as off-grid houses / cabins / caves (just kidding on the last one, but I'd bet that there're probably some fall-out shelters that do just that...) This probably applies even more so to lights meant for car interiors. I'm not familiar with any screw-in style 120VAC to 12VDC adapters that then allow you to screw in 12V lights. And will automatically bypass when 12VDC is present instead of 120VAC. That's probably the big problem: having both 120VAC and 12VDC and expecting the lights to automatically switchover (or be able to use both). That said, how about having a parallel "emergency lighting" system (or even day lighting for when electricity is most expensive and lighting demands are lowest)? You could still have the 'fun' of running romex (and cutting out knockouts for electrical boxes, running wires through walls, patching drywall, etc.) Losses (and you have losses with 50/60 Hz AC, which at that frequency, isn't all that different from straight DC) are a function of cable diameter. Wikipedia has a chart of the resistances of differing gauges (milliohm per ft or per m): http://en.wikipedia.org/wiki/America...AWG_wire_sizes So assuming a hundred foot run of 14 gauge (and good, low-resistance connections, and no high-resistance kinks), the resistance from one leg of the wiring would be 1/4 ohm. For the sake of calculations, I'll assume you have some 3W LEDs. Using the formula $P=V^{2} / R$, you can model the LED as a resistance of (roughly) 48 ohms: your wire resistance is pretty negligible in comparison. In comparison, most house-hold low voltage (12VAC for your central vacuum, HVAC, door bell, etc.) uses 18 gauge wire, and is run throughout your house. EDIT: Most of these low-voltage systems are also pretty low current: usually less than an amp. As for your second question, Google for peltier drink cooler: http://www.google.com/search?q=peltier+drink+cooler