Sensing Humidity With The SHT15 + Arduino

Discussions area for bildr's blog posts.
From: http://bildr.org/2012/11/sht15-arduino/

The SHT15 is a digital humidity sensor that outputs a fully calibrated humidity reading. And... because what we are measuring is actually relative humidity, and relative humidity being relative to temperature, the SHT15 has a builtin digital thermometer. This makes things much easier to work with than sensors without a thermometer onboard ...
ameyer
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Sometimes you can see things without actually seeing them. I look at bildr.com every morning to see in any new ideas have popped up. I wasn't really interested in sensing humidity but I've probably read the article at least three times. Not once, until this morning, did I notice: "...that is slimier to..". I usually reserve the word slimier do discussions involving politicians and other lower forms of life. ;)
Bodger
 
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Darn auto correct.

Bodger wrote:Sometimes you can see things without actually seeing them. I look at bildr.com every morning to see in any new ideas have popped up. I wasn't really interested in sensing humidity but I've probably read the article at least three times. Not once, until this morning, did I notice: "...that is slimier to..". I usually reserve the word slimier do discussions involving politicians and other lower forms of life. ;)
ameyer
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Location: The Bay Area

Very good article about sht15! I have some sensors like this and I try to take the most accurate measurements I can. What I've noticed is that when I connect a sensor to arduino in 3.3 volt output, before the connection the voltage is 3.26 and after the connection is 3.94v. This is one strange problem. A second one is that sometimes the voltage goes to 4.86v. I disconnect the power and ground and leave the SCK and DATA connections of sensor connected to arduino. I measure the voltage again in vcc and ground of the sensor and I get again 4.86v.
Can someone give to me a reasonable explanation for these facts? I want to calibrate the sensors I have and I want to be as precise I can be by supplying 3.3v in the input but these two problems mess things up!

Thank you in advance!
Nasicornis
 
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Joined: Sat May 26, 2012 6:47 pm

That's very strange. I have no clue how you are getting such high voltage from the 3.3v pin.

If you are using analog sensors you can set
analogReference(EXTERNAL);
in your setup, and then connect your sensor's power pin to the "AREF" pin to make sure the reference is always the power. So if it fluctuates, it will compensate.

You can read more here: http://arduino.cc/en/Reference/AnalogRe ... rence.AREF


Nasicornis wrote:Very good article about sht15! I have some sensors like this and I try to take the most accurate measurements I can. What I've noticed is that when I connect a sensor to arduino in 3.3 volt output, before the connection the voltage is 3.26 and after the connection is 3.94v. This is one strange problem. A second one is that sometimes the voltage goes to 4.86v. I disconnect the power and ground and leave the SCK and DATA connections of sensor connected to arduino. I measure the voltage again in vcc and ground of the sensor and I get again 4.86v.
Can someone give to me a reasonable explanation for these facts? I want to calibrate the sensors I have and I want to be as precise I can be by supplying 3.3v in the input but these two problems mess things up!

Thank you in advance!
ameyer
Founder
 
Posts: 3010
Joined: Thu Jan 21, 2010 11:59 pm
Location: The Bay Area


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