I am thinking about doing a project very close to this:
The last time I did an instructables project, I found out I could have made it a lot easier had I asked here first. So lesson learned! Anyone care to comment on what they would do differently with this project?
Are you up for using leds instead of bulbs?
If your up for LEDs, you should look at smart LED strips. If you google for "arduino smd5050" you will get started. Basically, you can set the colour (RGB) of every LED in the strip individually using only a couple of control outputs from your Arduino. You can keep joining strips together, but you will need to inject power as you go as there is a voltage drop. You can have a lot of LEDs drawing some significant current, so you will need a separate power supply but you would need this for any sort of lighting display.
There are many different sorts of strips, waterproof/non waterproof, different chips, different numbers of LEDs per metre etc.
Or WS2812B, with FASTLED.h library, or NeoPixel library at adafruit.com
Just 1 control line needed.
I think I will be doing a little of both. I have some regular christmas lights that I bought after christmas last year that I want to control as full strands. But I will be doing some neo pixels or something like them too. I've done those before and they are a lot of fun. But for this project I will just work on controlling the lights that I bought.
Are the lights you have DC with a transformer or AC? What is the voltage and current rating?
The instructable you linked to is switching AC current through opto isolated relays. While definitely feasible and a good approach, you need to be extremely careful as you are working with enough voltage and current to kill you. Unless you have some familiarity with AC wiring I would try and stick with DC as you might destroy some electronic components if you get it wrong but you shouldn't hurt yourself.
If you do go ahead make sure you insulate the AC part well (e.g. insulated project box) and connect it to a safety switched household circuit.
A lot of homes have 12V from the electrical box mainly for safer out in the yard use. IIRC some have 24V according to an Old Electrical Projects Book but I've only seen 12V (dunno about regulation) with more than a couple of Amps of fuse behind it.
If you run 120VAC/240VAC outside, it's going to need heavier insulated wire than indoor and hope you don't have many squirrels.
Good questions! I am pretty comfortable with residential wiring. I know the difference between neutral, hot and ground and I have wired several switches in my house. I looked at the lights that I bought and they are all "regular" light strands. No transformers. They have 110V plugs. I was planning on putting the electric distribution stuff in some plastic storage bins. That would probably be safe, but now you guys got me thinking.....
Are there LED strips with christmas light spacing, if you know what I mean? All of the LED strip lights that I have bought were one, short; and two, the lights were only a few cm apart. I'd like something that looks more like christmas lights. I don't want to spend hundreds of dollars on led strips, that's for sure.
If you are comfortable with residential wiring then you should be right. The relay is the switch, and you just have to connect your active wire to the correct terminals on the relay. On the relays I have used, from memory there is "Normally Open" (NO) and "Normally Closed" (NC) and a common terminal. The relay can make a circuit with the common terminal whether it is powered on or not. I usually can't remember which is which between NO and NC so test it with a multi-meter to see which one is connected to the common terminal when there is no power and connect your active to the other one.
If the LEDs on the strip are too close together you can just turn on every second or third LED to get the spacing that you want. Check the pricing on the LED strip that has the smallest number of LEDs per metre and if that is still cost effective for you then go for it. You can get some nice animation effects going up and down the strip 