Sunday, November 30, 2008

Gingerbread House Light-up Fun

My wife occasionally makes a gingerbread house to donate for a charity auction. Her houses always look great. (Gingerbread house tip #1: for stained glass windows, crunch up some Jolly Ranchers, put them in the window holes in already baked ginger bread, then heat in the oven. The Jolly Ranchers will melt together into a very nice looking edible stained-glass window!) (Gingerbread house tip #2: wives, allow your husbands to eat the ginger bread. You may think they're crazy, but their mom never let them when they were kids and they always wanted to. Now you have this opportunity to make your husband insanely happy.)

Her last house was a lighthouse. Being the manly husband that I am, I offered to put a light inside the light house tower. Of course, as with most of my projects, hilarity ensued.

Since the mini Christmas lights (usually) stay on when a bulb burns out, I always thought the lights were wired in parallel. Like this:


So, I should be able to just cut off all the other lights, leaving just one to be the ├╝ber cool lighthouse light, right? Wrong. When I tried this braniac experiment of mine, my reward was a spectacular flash and pop.

It turns out mini Christmas lights are wired in series, like this:



Which means I put 120 volts across a light bulb built for about 2.5 volts. Oops.

Of course, this begs the question, how does a string stay lit when a bulb burns out? It turns out to be a clever little wire looped around the base of the filament leads at the bottom of the bulb (see image at right). The wire is oxidized so it's usually insulated and doesn't conduct current. But, if the filament burns out, the oxidization is burned through and current is passed through the loop of wire instead. 

Simple, clever and effective. I hope the person who thought this up is paid .01 cents for every bulb made. (Probably not. It seems patents now days aren't used to reward clever designs, but rather exist just to give patent lawyers a job at patent troll companies.)

At this point I was having way too much fun learning about Christmas lights for my own good, so I stole away to the local hobby store and got a pre-made non-manly (but non-explosive) craft light for the gingerbread lighthouse. I still had to resort to stealing some ginger bread to eat when my wife wasn't looking.

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