PC thermometer schematic

Posted on Feb 19, 2013

This incredibly simple thermometer plugs on any free serial port. Does not make use of any programmable components as microcontrollers. It gives temperature readings accurate to 0.5°C with no calibration. It's cheap, so I've put one on any PC I use. And it is so nice to have the temperature shown on the Windows taskbar, that a million friends asked me to build one! Since I have no time to build a million pcTHERMs, I give you the plans and the software to build one on your own.

PC thermometer schematic
Click here to download the full size of the above Circuit.

This project is easy enough for beginners, the only difficulties possibly arising from serial port hardware incompatibility from PC to PC. In the single-sensor version, you need only the sensor IC, a voltage regulator and and handful of diodes and resistors. Build it, and learn the secrets of IIC bus, how to implement IIC bus using only two resistors and a couple of zeners, how to drive it on a serial port using Visual Basic .Components involved are available on the worldwide RS-components catalogue. displays both indoor and outside temperature on the Windows taskbar (see figure) plugs in any free PC com port range -20 ... +125°C (-4 ... 257°F) basic accuracy and resolution 0.5°C Centigrade (°C) of Farenheit (°F) scale data logging on easily readable text file sampling rate 1, 5, 30 or 60 seconds one or two temperature sensors (upgradeable up to 8) com port powered, no external power supply required easy to build, no exotic nor programmable parts inside no calibration required full source code available for free (educational and non-commercial uses only). The circuit is derived from the Claudio Lanconelli's PONYPROG programmer (I recommend you to visit the Claudio Homepage at http://www.cs.unibo.it/~lanconel ). The key component is the Dallas Semiconductor's DS1621 temperature sensor. This tiny 8 pin IC needs only +5 volts to measure the temperature and to send it out via its IIC bus output. Since many IIC...

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