Hello. I hope this is a good section of the forum to place this topic. I had just gotten my Arduino (Duemilanove) this past week and I'm having a good time learning with it. It's a good hobby to have.
Anyway, I was wondering if it would be feasible to make your own Christmas light chains. Has anyone ever done that or seen a strand of homemade lights? I had this idea to have them controlled with the Arduino for around Christmas time or whenever.
I am still very new to electronics, so this is my thought about how to make it. This is probably very wrong. Would it be like this
I've actually been thinking about doing something like this, but the more control you want over flashing patterns and such, the more wires you need in the string, so it'd've required a prohibitively large harness to get the level of control I had in mind. If you just want simple chase patterns, you can get away with 3 or 4 interleaved series which requires only 4-9 wires at any point in the harness (depending on how many series/parallel sets you have).
I'll also point out that when you consider the parts and labor involved in building up strings from scratch, it becomes very attractive to buy commercially made strings and hack them up as needed.
For efficiency reasons, you'll want to put LEDs in series as much as possible which means you'll want a higher voltage supply. See the hardware interfacing forum for that info.
I've used an SSR (solid state relay) with the arduino and LED xmas lights. Make sure the SSR can handle the load. I used 25 amp ones which are serious over kill.
This is using a string rated at 120VAC.
With with a serial in parallel out shift register string I can control several hundred of these.
Remember that SSRs will have a certain leakage current in the off state. ~10mA is not much to worry about with an incandescent lamp or motor, but is more than enough to visibly light a string of LEDs (albeit dimly). You can mitigate the problem to some extent by putting several LED strings on each SSR or adding a ballast load in parallel.