Sensirion SHTxx Humidity and Temperature Sensors
A class for interfacing to the SHT(11/15/71/75) sensors. This is a high accuracy humidity and temperature sensor with a digital output.
Humidity sensors are not very common, digital ones less so!
I will be monitoring air flows in a ventilation system and needed to measure the humidty as well as the common temperature measurement. These modules are not cheap (aprrox £20) but there is little other choice...
Here is a initial version of the class SHT_v1
You must call SHT.update(SHT_high) to update the stored values for the temperature and humidity.
I will be working on a more efficient version soon (will use tickers/interrupts instead of polling).
Have you used any of the honeywell sensors? HCH-1000 or HIH-4030? Analog, but the mbed has plenty of 12-bit ADC to work with...
That said, I plan to pick one of these up when I have the spare cash, do you know if there are issues with I2C? I read somewhere about it not being 100% compatible...
The HCH-1000 would need an oscillator circuit and a frequency to volatage converter or use of a timer on the mebed to measure the frequency.
The HIH-4030 seems to cost more than the SHT71 for less functions!
The SHT is not directly compatable with I2C which is why I wrote the class using direct pin drive. Basically the start condition is not compatable.
I work with remote weather information systems (RWIS) mounted around our nations roads. They use a combined RH/AT Relative humidity and Air temp by RMYOUNG. These are integrated devices with high resolution/accuracy and some are based on a chip humidity sensor. These SoC humidity sensors are very sensitive to dirty environments and since they have shifted back to a hair type sensor...
Just thought you would like to know if accuracy is a concern.
I have been working with your program. But i seem to be getting temperatures as 0.00c . I was wondering if we need to put up any pull up resistors?
I dont remember needing any extra components, but I haven't experimented with this device in a year now!
Will this work with SHT21 ?
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Stephen McGarry
Have you used any of the honeywell sensors? HCH-1000 or HIH-4030? Analog, but the mbed has plenty of 12-bit ADC to work with...
That said, I plan to pick one of these up when I have the spare cash, do you know if there are issues with I2C? I read somewhere about it not being 100% compatible...