Though the only issue is that with the OBEX in a state of change the link on that page to an Object to use with this sensor doesn't work. (For the moment).
I have the Parallax module of the SHT11 sensor and also purchased sensors from Andrew http://www.aestheticacoustics.com/SHT11_01.htm
Andrew provided excellent service and a good product.
The object by Tracy Allen reffered to in JLocke's post works and is well written and an education in doing the
required math for the sensor.
Tom/Publison, Thanks for the acknowledgements and praise on my module, I appreciate it!
SMBaker, I would definitely recommnd the Sensirion SHT1x series of sensors. They work very well with the Propeller and are easy to integrate into programs. Sensirion does make filter cap for it as well (part number SF1) that can provide protection for the sensor in adverse environments. As mentioned in Tom's post, my website for my module has a lot of info on using the module in general and if you do a forum search for "sensirion" you will find quite a number of threads. I do have SHT11 versions built up currently and we be building more of SHT11 and SHT15 versions this week.
Tracy Allen's most recent code is very easy to use and both his and Cam's in the OBEX can be modified easily depending on the source voltage you are using with the sensor. I have to give him a tip of the hat as my mentor in many ways when developing my module.
The SHT11 and SHT15 require so little current, that they can be powered directly from a Propeller's IO Pin. On my Quickstart HIB board, I have one of my modules plugged straight into 4 IO pins. I set one high for VCC, one low for GND, and the other 2 are the data and clock lines. Makes it easy just to plug a module straight into the Quickstart or other development board header and start playing.
I would be careful with these SHT1x hygrometers. Depending how they're handled (mishandled) in the build/supply chain you may get sensors that are not accurate. Sparkfun found this out the hard way. Now they have an automatic "rehydration" setup that reconditions these sensors.
Here's a link to Sparkfun's story about the SHT1x sensors:
Also, beware of the very low cost DHT11 temperature/humidity sensors. I bought a half dozen of them to fool around with. The temperature readings are within spec. But the humidity is way off, and it looks like a scalar correction isn't working. Others on the Web say the DHT11 type sensors work OK. Mine definitely do not - YMMV. There are also DHT22 type sensors that are in the same/similar form-factor as the DHT11 and AFAIK use the same technology but are higher performance and cost significantly more. I don't have experience with these sensors. I do know the proprietary one-wire protocol is slightly different between the DHT11 and DHT22 type sensors.
Drone, Sparkfun's write-up is a good lesson in why you should read datasheets before manufacturing PCBs with a unique part, but is mis-leading in regards to the concern with the SHT1x series of devices. The Sensirion datasheet states:
"After soldering the devices should be stored at >75%RH for at least 12h to allow the polymer to rehydrate.Otherwise the sensor may read an offset that slowly disappears if exposed to ambient conditions. Alternatively the re-hydration process may be performed at ambient conditions (>40%RH) during more than 5 days."
In other words, the offset reading is temporary even in ambient condition.
As far as Sparkfun's experience, here is a portion of what I posted to their write-up:
At work, we manufactured a product for a customer that had the SHT11 and the customer was unaware of the rehydration notes. I actually discovered it while reviewing the datasheet for other reasons. Keep in mind though that Sensirion does not declare it as a requirement and the risk of offset readings can be minimal in some cases. Per the additional comments in the datasheet and from my experience, finished goods that were stored in a typical warehouse in normal packaging for several weeks, would not show any signs of offset readings. The polymer rehydrated from the natural environment which had a typical humidity of 35-45%. Even though the customer did not follow the procedure for close to a year, they never had any issues with the ~3,000 units that were manufactured. (every single unit was validated for accuracy during deployment of the product at an install site)
smbaker
Posts: 164
Comments
Though the only issue is that with the OBEX in a state of change the link on that page to an Object to use with this sensor doesn't work. (For the moment).
The Parallax Temp/Humidity Sensor is a good one.
Propeller demo code can be found here:
http://obexclassic.parallax.com/objects/search/?q=Humidity&csrfmiddlewaretoken=2eb1bf6de593b6b69ee38ada76497da5
or search the forums for more code.
And Andrew may have some more for sale:
http://forums.parallax.com/showthread.php/99043-For-Sale-Again!-WBA-TH1M-Sensirion-SHT11-Temperature-Humidity-Sensor-Module/page3?highlight=Humidity
I am using on of these with Propeller code.
Jim
http://forums.parallax.com/showthread.php/146679-Prop-driver-for-Sensirion-SHT1x-SHT7x-integer-math.
It's a good little sensor; I'm using a Parallax module and another SHT11 sensor mounted to a board of my own in my temperature/humidity data logger.
Andrew provided excellent service and a good product.
The object by Tracy Allen reffered to in JLocke's post works and is well written and an education in doing the
required math for the sensor.
Tom
SMBaker, I would definitely recommnd the Sensirion SHT1x series of sensors. They work very well with the Propeller and are easy to integrate into programs. Sensirion does make filter cap for it as well (part number SF1) that can provide protection for the sensor in adverse environments. As mentioned in Tom's post, my website for my module has a lot of info on using the module in general and if you do a forum search for "sensirion" you will find quite a number of threads. I do have SHT11 versions built up currently and we be building more of SHT11 and SHT15 versions this week.
Tracy Allen's most recent code is very easy to use and both his and Cam's in the OBEX can be modified easily depending on the source voltage you are using with the sensor. I have to give him a tip of the hat as my mentor in many ways when developing my module.
The SHT11 and SHT15 require so little current, that they can be powered directly from a Propeller's IO Pin. On my Quickstart HIB board, I have one of my modules plugged straight into 4 IO pins. I set one high for VCC, one low for GND, and the other 2 are the data and clock lines. Makes it easy just to plug a module straight into the Quickstart or other development board header and start playing.
Here's a link to Sparkfun's story about the SHT1x sensors:
www.sparkfun.com/news/1090
Also, beware of the very low cost DHT11 temperature/humidity sensors. I bought a half dozen of them to fool around with. The temperature readings are within spec. But the humidity is way off, and it looks like a scalar correction isn't working. Others on the Web say the DHT11 type sensors work OK. Mine definitely do not - YMMV. There are also DHT22 type sensors that are in the same/similar form-factor as the DHT11 and AFAIK use the same technology but are higher performance and cost significantly more. I don't have experience with these sensors. I do know the proprietary one-wire protocol is slightly different between the DHT11 and DHT22 type sensors.
http://www.buyincoins.com/new_en/details/new-dht11-digital-temperature-and-humidity-sensor-moudle-probe-for-arduino-product-11619.html
also available without board
http://www.buyincoins.com/new_en/details/new-dht11-digital-temperature-and-humidity-sensor-product-6732.html
Documentation: http://www.micro4you.com/files/sensor/DHT11.pdf
"After soldering the devices should be stored at >75%RH for at least 12h to allow the polymer to rehydrate.Otherwise the sensor may read an offset that slowly disappears if exposed to ambient conditions. Alternatively the re-hydration process may be performed at ambient conditions (>40%RH) during more than 5 days."
In other words, the offset reading is temporary even in ambient condition.
As far as Sparkfun's experience, here is a portion of what I posted to their write-up:
At work, we manufactured a product for a customer that had the SHT11 and the customer was unaware of the rehydration notes. I actually discovered it while reviewing the datasheet for other reasons. Keep in mind though that Sensirion does not declare it as a requirement and the risk of offset readings can be minimal in some cases. Per the additional comments in the datasheet and from my experience, finished goods that were stored in a typical warehouse in normal packaging for several weeks, would not show any signs of offset readings. The polymer rehydrated from the natural environment which had a typical humidity of 35-45%. Even though the customer did not follow the procedure for close to a year, they never had any issues with the ~3,000 units that were manufactured. (every single unit was validated for accuracy during deployment of the product at an install site)