Do It Yourself Christmas Tree light dimmer.
Why would you want a light dimmer for your Christmas tree?
One reason might be that it's a warmer and cozier light and more in keeping with the look of candles from centuries past.
The reason that has influenced me, over the past several years is that it's very tough to find a bad bulb when one fails. By reducing the voltage applied to the bulbs, the life of the bulbs are greatly extended. A 10% reduction in voltage doubles the life of the filament. Finding a bad bulb is even harder on the pre-wired trees that are popular these days.
I made a new dimmer this year because we added a tree at our house for a total of three. There's the biggest one in the living room that has the presents under it. That one is not very visible from the street in front of the house, so we added a slender one in the hallway by the front door that is very visible from the street. This year we added another one in the dining room.
Here's what you start with, all parts came from one trip to one store, Ace Hardware, the store closest to our house. Similar parts can be obtained from anywhere that has electrical parts, Lowes, Home Depot, etc.