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Designing FPGA-based vacation light controller

Posted: 21 Jun 2012 ?? ?Print Version ?Bookmark and Share

Keywords:dimmer switches? infrared? remote control? FPGA?

A few years ago, my wife and I were thinking of having a two-week vacation. At that time, we lived in a less-than-ideal neighborhood (we were once awoken at 2am by the sound of a SWAT team a few houses down the block, though that was certainly more extreme than a typical day in the 'hood). Anyway, we didn't want anyone to know that our house was empty while we were gone. So, like most folks, we considered purchasing a few inexpensive lamp timers to give the appearance that we were home. The only problemwe didn't have any lamps! All of our lighting was overhead.

However, we had recently remodeled a few rooms in our 95-year-old house, and decided to "go modern" by installing dimmer switches with infrared remote control in a few key areas (figure 1). These dimmers are drop-in replacements for your existing light switches, and are sold at most home-improvement and lighting stores. They are ideal for reading before bed, or controlling the lights on movie night.

Figure 1: Lutron Maestro dimmer switch with infrared remote control.

Being a typical tinkerer, it didn't take long for the wheels to start turning. I figured, why not put together a gadget to automate the lights via infrared control? And it would be better than lamp timers, because I could synchronize the lights to make it appear as if people were moving from room to room! The living room lights would go out after the evening news, then the bedroom light would come on for a while, and eventually all lights out until morning.

The simplest way would probably be to wire up some kind of controller to the manufacturer's remote control to simulate button-presses, but where's the fun in that? Besides, tampering with the remote would have earned me some serious time in the doghouse (wives tend to frown on that sort of thing)! So instead, I decided it would be fun to generate the infrared signals on my own.

Figure 2: Block diagram of the light controller.

I had recently purchased a Xilinx Spartan3E Starter Kit, so this seemed like the ideal place to start. I could use the FPGA as the 'brain' of the gadget, and simply wire up a few infrared LEDs to the I/O pins on the development board. I could run some cables to each room, with an LED on the end of each cable to point toward the dimmer switch. Additionally, the development board had buttons and knobs for input, as well as a Character LCD for convenient information display. (Photos of the completed system are at the bottom of the article).

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