Hacked Gadgets Forum

April 2, 2007

Temperature Logger using DS1820 and PIC 16L84 Microcontroller

at 5:55 am. Filed under Complex Hacks, Computer Hacks, DIY Hacks, Electronic Hacks

There has been quite a few temperature devices featured here in the past. This temperature logger is nice since it uses one of my favorite temperature sensing chips, the DS18B20. This sensor is digital and does not need any calibration. When I make my next batch of home brew beer there will definitely be a DS18B20 floating in it. Or if I have some extra DS1822 devices from the fish tank light project I might just use those…

“The logger probes measure temperatures from –55°C to +125°C (–67°F to +257°F). No calibration required.

A PIC Arbiter acts as interface between the Dallas temperature sensors and a logging PC. There are 8 terminations or single wire busses. Each of the 8 busses can support up to 8 sensors. As many sensors can be installed as required, limited to 64 maximum.

I have called it an Arbiter as the controller negotiates with each probe on the single wire bus. Each individual Dallas temperature sensor unique serial number. Where a particular probe is in relation to its peers, or particular bus pin on the PIC is irrelevant. The Arbiter sends to the PC the unique serial number of the temperature probe and its temperature in a serial frame.

The PIC Arbiter identifies sensors on each bus. Additional sensors can be plugged in at any time. Each device is polled every five seconds: its address and temperature data are sent via a RS232 serial link to the PC.”