This temperature monitor has been constructed using mbed microcontroller, DS1620 IC, NTP, and ThingSpeak website.
Using a digital temperature sensor IC DS1620, the temperature is monitored by an mbed microcontroller LPC1768 Cortex-M3. The time is retrieved through the network time protocol (NTP) and along with a time-stamp, the current temperature is then logged to www.thingspeak.com. Also used in the build are the RJ-45 Ethernet MagJack and a 100K Ohm resistor. The temperature sensor needs to be connected to the mbed and the DS1620 sensor is very simple to use.
The source code is responsible for configuring the sensor, connecting to the internet, and then run a loop which first retrieves the time using NTP Client, then retrieves the temperature from the sensor, and finally submits it to ThingSpeak using HTTP Client through their API. Using bit-banging the 3-wire bus, LSB first, the mbed communicates with the DS1620.
To run the mbed without keeping the computer ON all the time, a DC power supply was connected to the mbed. The device can be left in a green house, outside, inside, and monitor temperature from anywhere in the planet that you may desire. Link to project...