Sunday, November 25, 2007

Ha HA! Triumph!

Blogging is oddly cathartic. When I find myself frustrated to the point where I can't think straight anymore, it's nice to be able to kick back with a big giant drink and write about it.

Strangely, as I was writing about maybe needing the low voltage Fluke VoltAlert, I got to thinking about why I would need the low voltage VoltAlert. Christmas tree lights have the bulbs strung in series connections of 25 or so bulbs, and then they have a bunch of these strings in parallel so that if you unplug one light, you lose only the series that that particular bulb is part of and not the stuff in parallel.

Now, each of the series-connected strings divides the voltage across the bulbs such that if the string is working, each bulb sees a progressively lower voltage. That explains why the VoltAlert (which is only good down to 90V) can't find voltage present in the last bulb of a string but can in the first. However, if you unplug the last bulb in the series, suddenly there is no current, and every bulb sees the line voltage, and will light up the VoltAlert. I tested this on a working series just to make sure.

Now, the very first light in the bad series didn't register any voltage. I unplugged its bulb just to make sure there were no downstream shorts (though that should have blown the fuse), and still no voltage. That means a bad supply line, not a bad bulb. I'd been searching for the wrong thing last night, in the dark, in the cold, with the lights strung up on a snow-covered tree.

So I started at the plug and found that the supply was fine. I followed it along with the VoltAlert, and within 30 seconds found a place where the wire was severed. A couple minutes later after judicious application of a soldering iron and a water-proof wire nut, and the lights were back in working order.

Sometimes, it helps to work during daylight hours.

My luck with the HO trainset I tried to set up under the tree today was much more agonized. It's a trainset I've had since I was a kid, but it was nailed down to a sheet of plywood forever, and my parents just brought it here on their last visit. It sat in a suitcase since then. Until today when, in a momentary lapse into good parenting, I decided to show it to MaxieC.

I think it's kinda sorts working now. It's very hard to run HO tracks on a carpet, so I cut out a platform for it out of 1/2" blue rigid styrofoam insulation I had left over from the garage door insulating project. I still need to tack down the track and shim the turns, though, as there is still a tendency to roll over at the corners and for the track to separate if the foam is bumped.

I haven't hooked up any accessories yet.

3 comments:

blogauthor said...

I am really impressed that you fixed the lights instead of just buying a new string for $5.99. My dad does all of my christmas light, if not, we would have no christmas lights.

We are going to buy Offspring an O gauge train for Christmas (shhhh, don't tell him). Wheeler has gads of track and old trains from his dad and his dad's dad. It will be really cool. I have always wanted to put a train around the tree, so it will be cool to do it next year. Post a photo of yours?

Rhonda said...

It's awesome that you set that train up!

We have (now dismantled) one of those plywood concoctions of track and tree and plaster of paris shtuff from when our boys were young...
making memories (even if you need a tall glass of that snowshuvvle drink thing)...

Manly lesbian said...

Cool beans - someday I will get a train and build it with all my ceramic houses - as soon as I get a house large enough to put it all in. Hmm.. I could moove in with you and bring all my houses and set it all up in your basement...