Hi, I'm a complete newbie when it comes to Arduino but I've got a project that I'm really excited for. I'm looking to create a whole home temperature monitor but I need some quick clarifications from someone more knowledgeble than me.
I'd like to monitor up to seven areas of my home and possibly monitor humidity as well. I'm somewhat confused as to what temperature sensor I should start with, can someone please shed some light?
I've seen various sensors that would work:
LM35 - Inexpensive, many examples online
SHT10 - Inexpensive, examples online, Humidity sensor also
SHT15 - Expensive, not many examples online, Humidity sensor also
SHT7x - Not much information at all
Questions:
Can I run up to 7 of these sensors from one Arduino
Can I run these sensors over a long distance (30 feet)
Are there any other temperature/humidity sensors I should be looking at?
For long distance runs, 1-wire (ds18s20) is hard to beat. You can put several sensors on the same 1-wire bus. It is designed to work at 100m.
The LM35 analog sensor will be subject to noise over long runs - someone posted here recently with a problem doing just that.
The other sensors you mention are, IIRC, short run TTL level bus interfaces. These are designed to run a few inches, not all over the house. I doubt they would even work stretched out tens of feet. You may find some bus extension ICs.
If you want to do individual temperatures, you could use 10k resistors. I work in HVAC and we use them all the time. You can also do temperature averaging using 4 sensors; 2 sensors in series and paralled with another 2 sensors in series. If your home isn't terribly large (less than 2,500 square feet) you can probably just use a single humidity sensor, unless you have a humidity problem in one particular area. I think the SHT10 is a fine choice. Our best controls use these. Be aware that if you use them, you should only power them and take a reading every 6 seconds or more. Any more often than that and you'll start to see some inaccuracies due to internal heating in the sensor. It's buried in the sensirion datasheet.