thermometer circuit

Posted on Feb 6, 2014

When the system is placed in a shop or mall, logos and product advertisements are a perfect complement to temperature information. For home use, photos of the kids at the beach or should the temperature drop- in the making of Mr. Snowman are a nice gift for Grandma. Other application areas include hotels, airports, sport resorts, and tourist si

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tes. Despite of its rich feature set, the DVD-thermometer is an amazingly simple design that requires very few components thanks to an ingenious mechanism. And it is hundreds of dollars cheaper than the typical PC-centric solution. The circuit is battery operated, and fits comfortably a small plastic box, located in front of an ordinary DVD-player. A switch and an infrared LED peep out of the box. The DVD-player is loaded with a disk, pre-recorded with all of the pictures corresponding to different temperatures, in a well-known order. Acting as an intelligent infrared remote control, the DVD-thermometer directs the player, selecting the scene that matches ambient temperature. I made the DVD-thermometer at home, for the fun of doing it, with no special tools other than a soldering iron, a multimeter, a PC with ordinary CD-R burner, and the Motorola QT demo board. I submitted it to the "Flash Innovations" Design Contest sponsored by Motorola, and it won the "Distinctive Excellence Prize". The circuit diagram is embarrassing simple: it is entirely built around a cheap 8-pin microcontroller, a digital temperature sensor and an infrared LED. The hard work is delegated to the software, which is the most important ingredient of the project. I wrote the program in C, implementing low-power techniques, with code reuse, portability and data encapsulation in mind. As a result, all of the modules reside in separated files, ready to be...

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