A Temperature Data Logger using PIC12F683 and EEPROM

Data loggers are electronic devices that record data over time with a built in instrument and a sensor. They are generally small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors.The data logger we are talking about records temperature of a given place over time. This project uses a 8-pin PIC12F683 Microchip along with a serial EEPROM and a thermistor (temperature sensor).

The temperature is measured and stored at user programmable intervals; this can be from 1 second to 256 seconds. The time interval is set by programming it and the start time into the EEPROM. Since most of the time the PIC stays in sleeping mode, this consumes very less power. With a EEPROM of 32KB, it is possible to record 32,000 measurements. This could be one measurement every 1 minute for 22 days for example.

Source: http://www.gedanken.org.uk/electronics/temperature-recorder/pcb-v1.jpg

The combination of thermistor and analogue circuit gives a range of between about -40 °C and +100 °C although the linear range is just between about -10 °C and +40 °C.

The firmware for PIC is written in assembly, and the EEPROM, PIC and external connector all share the same I2C bus. The EEPROM address keeps incrementing in this case so that breaks in the data can be seen.
When the temperature measurement is not being made the PIC goes to sleep. It is woken once a second to make a measurement. The sampling interval is stored in a fixed location in the external EEPROM and is read at power up.

Read full details here:

Temperature Logger