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The simplest relay board you can get is a "Kit 74". They cost about US$25 (shop around!), or in Australia you can pick one up off the shelf at a Dick Smith store for just under $50. They're designed to plug directly into your PC's parallel (printer) port, and has 8 coil relays. The way these work (basically) is that when a voltage is applied to the coil, it creates a magnetic field which moves the switch from the OFF to the ON position. When you remove the power, the switch moves back to the OFF position.

These are great for learning how these things work and debugging (the LED's go on when the relay is turned ON). Not great for high speed switching. I read somewhere that these relays (the blue bits on the photo) are rated at only 2 switches per second, and they're mechanical, so they're eventually going to wear out. I use the one I bought to switch the mains power to the shelves. The board is rated to switch 5amps at 240VAC (the relays themselves are rated to 12amps).

This photo shows the top (opto-relays) and bottom (with the LED's) view of my relay boards. Each has 16 opto-relays, and you guessed it, connects to the controller using two RJ45 and CAT-5 cable. The design is extremely simple!

Each relay has a 220ohm resistor infront of it, and there's a high output LED as well to show the status of the relay. All the circuits are connected to a shared earth wire connecting back to the controller.

And, it also just so happens that each shelf (of power adaptors) has 14-16 devices.

So what is needed is a way to switch fast... very fast when you're thinking of synchronising your lights with music. The answer is solid state relays. The +5 volts (to indicate that the circuit should be turned on) that is output from the controller connects to an optoisolator. Very basically - inside the optoisolator is a small LED, which, when power is applied (+5v) lights up and shines on to a receiver (phototransistor). When the phototransistor has light on it, it opens the circuit. Apart from the speed (it takes around 5 thousandths of a second to turn on/off) is that because it is optically switched (there is no physical connection between the high voltage world and your controller), it offers protection to your controller - and will never wear out.

When researching & designing how I was going to do it, I got a lot of information from ChristmasLights.NetBootDisk.com and I recommend this web site as a good source of information.

The picture to the right gives the basic design for solid state relays. You just need one of these for every set of lights you want to control - yes MORE soldering! The way I implemented this design was to use integrated components (the optoisolator and the Triac are integrated into the one sealed component), this cuts down on the complexity of the circuit somewhat.

You just need to be careful of the spec's, whether they're designed for AC or DC, the voltages and current. The opto-relays I've bought here are rated at 2amp, 12-240volt AC. The Part number to look for is: G3MB-202 PEG, and they cost about US$5 each (again shop around!). I'm also using relays bought locally, Part number to look for is OAC5A (or RL6 at oatleyelectronics.com). These are only rated for 120v, which is good enough, and work out about the same as importing the other ones from the US.

UNDER DEVELOPMENT
More info - Controller
More info - Relay boards
More info - Sequencing software
~~More info - Countdown clock~~
More info - Wiring / Power
More info - Mounting
More info - Videos