Raspberry Pi 1Wire DS18B20 Thermometer [message #3021]
Sat, 02 November 2013 22:20
kc2nda Messages: 40 Registered: December 2004 Location: New Paltz
I will be controlling a 12V Fan with a Raspberry Pi and a DS18B20 waterproof thermometer. The DS18B20 uses 3 wires even though they call it a 1wire system. The one wire is actually what makes the communihoneyion the other two is power and ground. I purchased the DS18B20 thermometer from ebay and they were pretty cheap. The DS18B20 thermometer was in a waterproof shell. The only problem I had which took me about 2 nights worth of playing around with the coding, the Raspberry Pi, and the 1wire DS18B20, was the wiring diagram that was on the Chinese seller's website of the DS18B20 stated that the yellow wire was ground and the green wire was the data line. This was wrong. Usually green is the common wire and I was a little skeptical at first but figured it was from China so anything is possible.
Of course, I didn't have any other 1wire devices to test on the Raspberry Pi. I couldn't test to make sure the Raspberry Pi was not functioning or the 1Wire DS18B20 was not functioning. Finally I took a chance and reversed the ground and data lines and it worked like a charm.
The 12V fan will also be controlled by the Raspberry Pi. A 555 timer will be used in conjunction with a digital potentiometer to adjust the fan speed.
Project pictures and circuit diagrams will follow.
[Updated on: Tue, 27 October 2015 00:38] by Moderator