This is extremely simple to build PIC Temperature meter that allows to measure temperature in two different locations at the same time. Never before such a useful and powerful circuit could be built with so little components and yet provide endless possibilities. This is all possible thanks to the use of PIC16F628 microcontroller and 2x16 character LCD display that act like a small computer which can be customizable thanks to upgradeable hex firmware.

Presented PIC temperature meter uses two very exciting DS18S20 digital temperature sensors that come in convenient TO92 package. Unlike regular sensors where temperature readings are passed as varying voltage, DS18S20 passes temperature information in a digital format as data. This brings many new possibilities and enables to pass temperature information over much longer distances just over a two wire cable. With this temperature can be measured in different locations at the same time and away from the main circuit board. With regular sensors which rely on the varying voltage cables must be as short as possible because longer wires introduce stray resistance that bring unreliable readings.

Another great feature of DS18S20 sensors is that they don't require any calibration at all, while providing 100% accuracy out of the box. That means that you just plug it in and forget about spending time for recalibrations! This is all due thanks to the nature of sending information in a digital format. In fact DS18S20 is just like a computer connected to the network that has a unique serial number identifier similar to an IP address. Multiple DS18S20 sensors can send information simultaneously, even over the same two wire bus cable. The two wires provide 3-5V voltage supply to the sensors and are also used to pass data in two different directions. If wires are very long so that voltage on DS18S20 sensors is below 3V, external voltage supply can be used, or resistance of 1K resistors can be further decreased.

Once PIC microcontroller receives temperature information it converts it into both Celsius and Fahrenheit values so that they can be displayed on LCD display. PIC temperature meter is capable of measuring temperatures from -55 to 125 °C degrees Celsius (-67 to 257 °F Fahrenheit) with 0.5 °C / 1 °F accuracy. If you just need to measure the temperature in one location you may just use one DS18S20 sensor and PIC16F628 microcontroller will automatically pick it up.

Additionally the way the temperature is displayed on LCD display can be customized by pressing a tactile button. Each selection is saved in non-volatile EEPROM memory so that PIC remembers it even after the voltage supply is disconnected. Requests for different display styles are welcomed and can be upgradeable by simply flashing PIC16F628 microcontroller with a new hex firmware.

We have also plans to release a temperature thermostat controller version in the near future that will turn on/off devices when certain temperatures are reached. Thermostat can be used to turn on heaters or fan / air conditioning system.

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