Tuesday, July 7, 2009

ClockIt - 7-segment strings


My unhealthy obsession with the ClockIt clock from SparkFun continues. I like how simple it is. It's a microcontroller directly wired to a 4 digit LED display, a piezo speaker, and a few switches. I'm finding it a good project for getting used to working with gcc-avr directly without the "training wheels" offered by the arduino platform. In the video you can see that I've written some code to display alpha-neumeric strings. I followed suggestions on Wikipedia on how to represent some of the more complex characters. It's a little weird, but you get used to it. My end-goal for this project is to have the clock spell out the time in English. Pointless, but instructive.

I'm thinking I could also have it tell me what electricity rate we're currently on as part of PG&E's net metering scheme (peak, partial peak, or off peak). In order to do this properly I'd have to support the date as there are different daily schedules for the summer and the other seasons. The same functionality might work better as an ambient orb like device. It could be red for peak, yellow for partial peak, and green for off peak. I'll have to think about which I'd like to do.

Some other project ideas I have for the clock are a kitchen timer (obvious I suppose), and a thermometer using a 1-wire digital thermometer IC connected to the one free I/O pin on the microcontroller. I already have some code written for the kitchen timer idea although it needs some clean-up before I post it.

Incidenally, SparkFun recently published the PCB layout files for ClockIt under a creative commons share-alike license making it one of their first open hardware projects. The layout files are for the Eagle layout software by CadSoft. There is a free version of Eagle for non-commercial use that allows you to create 2-sided PCBs up to 4x3.2 inches in size. SparkFun offers a PCB fab service to implement your design for $2.50 per square inch.

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