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Author Topic: Arduino UNO and low cost humidity sensors  (Read 502 times)
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Hi all!  I have successfully built an online thermometer using the instructions of the Arduino practical book and misc online resources (http://www.freetronics.com/pages/online-thermometer), using a Dallas DS18B20 and a small 4K7 resistor, and its working fine!

Next I'd like to upgrade the setup with a humidity sensor of some sort.  I dont have many requirements for this sensor and I am searching for a relatively low cost sensor as well as installation instructions along with all necessary items (shopping list if you will)..

Basically, I'd like the sensor to be:

able to read humidity levels between 0 & 100% (d'ah.. smiley
have a resolution (precision) of +/- 2 to 3% (Am I too demanding here?)
Costing less than $20 USD
Use as little setup as possible...  Basically, a 3 pin connection is fine (like the Dallas thermal sensor).

It will be installed on a standard 3 wire cable like the Dallas sensor...  It will be located remotely from the arduino board (approx. 20 to 50ft).


Can someone recommend a sensor??  There are tons of sensors onthe internet, I am confused which one should I go for to have the best compatibility and performance for my needs without going for a very expensive research-type sensor.... All I want to do is monitor the humidity level in my house...

Waiting for your replies!!!!

Thanks!
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Yes the AMS 2303 (DHT 22) humidity sensor will do all you specify except the RH accuracy which is 5%.
I don't however think that it will function with 20' of wire though. A simple OOK radio transmitter and a 328 programmed to read the sensor every 5 minutes and transmit the data via 'Virtual Wire' would be trivial to assemble and program. There are sketches in plenty with good examples and code as well to do what you want to do. Adafruit sells the sensor and has a good library for the sensor. The radios are typically $3 - $4.00 a pair and are available from many places. The Virtual Wire Library is free from the Playground here.

Bob
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Good tutorial: http://learn.adafruit.com/dht
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Yes the AMS 2303 (DHT 22) humidity sensor will do all you specify except the RH accuracy which is 5%.

Is it common for such low cost sensors to have a +/- 5% resolution???  Its not that its too big but I'd like less than 5% if possible... Otherwise, if more sensitive sensors are very expensive, Ill take the 5%...


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I don't however think that it will function with 20' of wire though.

I dont want to play with radio transmitters.... Its not reliable.  Wired is the only option.  Why do you say the DHT22 wont work with wire??  Is it because of the length?
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