Christmas window candles

We’ve been putting LED “candles” in the windows the last several years. Having tried a couple different commercially-available varieties and having been uniformly disappointed, I thought that I might as well make my own.

I can’t quite get over that it seems like terrible technological overkill, using an ATmega328P and a DS1307 RTC just as a lamp timer. But I guess that’s one of the great things about this stuff, even under-utilized, it can be quite economical. The electronics for these worked out to around $15 per copy. Add a couple bucks for wood and CPVC pipe, and they’re still quite competitive with examples at the local big-box stores or on the web. And they work exactly the way I want!

I’d previously made some RTC breakout boards, so I just plug them into the main board, so that I can re-purpose them off-season if desired. Although it would have been fun to try to develop a candle-flicker algorithm with PWM or whatever, I got lazy and just got the LEDs with the built-in flicker chip from Evil Mad Science.

So quick-and-dirty, but it was also a fun little project, and it does something that I want. They look quite convincing from the road! More pictures here.

Couldn't you have done with with a smaller and cheaper AVR though? A 328p seems a bit of an overkill to drive 3 LEDs. :) Cool display though.

KirAsh4: Couldn't you have done with with a smaller and cheaper AVR though? A 328p seems a bit of an overkill to drive 3 LEDs. :) Cool display though.

Undoubtedly. Gave some thought to using an ATtiny, which would have saved a couple bucks a copy. Hadn't done an I2C interface with an ATtiny though, so it came down to my time and effort to figure that out vs. a few extra bucks. Since I was only making a few, I took the quick/lazy way out.