Step 1 : Introduction


There are multiple ways to control Christmas lights via a Computer. If you are just getting started, using the Parallel port is a good starting point in my opinion. (X-10 is another option. X-10 is probably a little cheaper and easier, but there are issues with speed and scalability.) With just a little bit of electrical knowledge and some fairly common equipment, you can control up to 8 circuits per parallel port (max of 3 ports per computer without needing to know anything about integrated circuits. Plus, if you do plan to upgrade to a more complex parallel port control method (or use digital I/O boards), all you need to do is change out the 5Vdc interface and these boxes are ready to go in your new environment. (Full image)

Step 2 : The Parts

Solid State Relays (SSRs	I use 10A 120V Relays. You can usually find them for $3-$10 a piece, used. You'll need 8 of them. Since you local hardware probably doesn't carry these, you might want to check out All Electronics or MJPA, Inc	$40
Bulk Wire (14 gauge)	5 feet of black, 5 feet of white is plenty. I usually find this at about $.10/ft	$1
14-3 Wire (I prefer Rubber coated.)	$.60/ft or so. Depends on what you get. 10ft or less.	$6
Pig Tail (14 gauge)	Be careful. Don't go smaller that 14 Gauge. If you shop around you can usually find a good deal on these. Alternatively, you can make your own.	$3
Crimp Connectors	These are really optional. I just prefer them to wrapping wires around terminals.	$5
Machine Bolts with nuts	Or something else for connecting your SSRs to your project box.	$5
120V Indicator (optional	Lots of people place these on each box they build. I personally just have 8 wired to some electrical plugs for debugging. That way I can easily move them from box to box for testing SSRs.	$8
1/2" Wire clamps	Depending on your exact configuration, you might use 5-10 of these guys. (The are used for clamping the wires to your project and metal boxes.) A bag of 10 cost about $6.	$6
two 4x4 electrical boxes to hold the outlets	Cost will depend on meta vs. plastic. My metal boxes with covers cost about $4.50 a piece.	$8
4 outlets	White, brown, black, whatever	$4
Box to hold the SSRs	Projects boxes can really range in price. I got lucky and found a number of perfectly sized boxes for $1.50 a piece. Normally, I would pay $8-$20 for a x-large Project box.	$12
DB-25 Wire	As long as one end fits the computer, it really doesn't matter what is on the other end. (Your going to cut it off unless of course you want to solder a connector onto your control box.)	$5
Tools	Screw Divers, Drill (doesn't need to be power), pliers, wire stripping/crimping tool, knife, and an ohms meter all assisted me.	-
Total:		~ $100

$100 is probably a a high water mark. Buying in bulk or shop around for deals can really lower the price. Also, SSRs can be built a lot cheaper than they can be purchased, but that requires some knowledge of integrated circuits; something this how-to is trying to avoid.

Standard disclaimer: I'm not responsible for anyone hooking these circuits up and the results that follow their use.

Step 3 : Schematic

Here is the end wiring result. Pins 2-9 are the control (positive)wires going to the box., while pins 18-25 can all be used for grounding. (Picture)

Step 5 : Solid State Relays


Solid State Relays (SSRs) are the heart of Parallel Port Control Boxes. I find it easier to purchase pre-built SSRs, but you can build them(rather cheaply) if you know what your doing. Drew Hickman provides some good information on his Christmas site for building SSRs. If you shop around, you can usually find used 110V 10A SSRs that will work with 5 vdc input for under $5 a piece (sometimes $3).

All a Solid State Replay really does is allow the 110V AC current to pass through when 3-8V DC is applied, and opens the AC circuit when the direct current is not present. (full image)

Step 6 : Relay Boxes


You'll need a box (plastic or metal, it really doesn't matter) to hold your eight solid state relays. I've seen others use large boxes (14" x 14") and some (like me) use small (9" x 5" x 1.5") boxes. I found a good deal at All Electronics on some used boxes ($1.50), so I went with those.