Adafruit Si7021 Manuale utente
Adafruit Si7021 Temperature + Humidity Sensor
Created by lady ada
Last updated on 2018-11-21 06:58:57 PM UTC
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Guide Contents
Guide Contents
Overview
Pinouts
Power Pins:
I2C Logic pins:
Assembly
Prepare the header strip:
Add the breakout board:
And Solder!
Arduino Code
Install Adafruit_Si7021 library
Load Demo
Library Reference
Python & CircuitPython
CircuitPython Microcontroller Wiring
Python Computer Wiring
CircuitPython Installation of Si7021 Library
Python Installation of Si7021 Library
CircuitPython & Python Usage
Full Example Code
Python Library Docs
Downloads
Files & Datasheets
Schematic
Fabrication Print
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 2 of 19
Overview
It's summer and you're sweating and your hair's all frizzy and all you really want to know is why the weatherman said
this morning that today's relative humidity would max out at a perfectly reasonable 42% when it feels more like 77%.
Enter the Si7021 Temperature + Humidity Sensor - the best way to prove the weatherman wrong!
This lovely sensor for Silicon labs has ± 3% relative humidity measurements with a range of 0–80% RH, and ±0.4 °C
temperature accuracy at a range of -10 to +85 °C. Great for all of your environmental sensing projects. It uses I2C for
data transfer so it works with a wide range of microcontrollers.
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 3 of 19
We put this nice sensor on a breakout board with a 3.3V regulator and level shifting so you can use it safely with 3.3V
or 5V power & logic. There's a PTFE filter to keep the sensor clean, that's the white flat thing on top. Also comes with
some pin header. Some light soldering is required to attach the header but it's easy to do.
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 4 of 19
Pinouts
The Si7021 is a I2C sensor. That means it uses the two I2C data/clock wires available on most microcontrollers, and
can share those pins with other sensors as long as they don't have an address collision. For future reference, the I2C
address is 0x40 and you
can't
change it!
Power Pins:
Vin - this is the power pin. Since the chip uses 3 VDC, we have included a voltage regulator on board that will
take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your
microcontroller - e.g. for a 5V micro like Arduino, use 5V
3v3 - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
GND - common ground for power and logic
I2C Logic pins:
SCL - I2C clock pin, connect to your microcontrollers I2C clock line.
SDA - I2C data pin, connect to your microcontrollers I2C data line.
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 5 of 19
Assembly
The photos below show a an HTUD21 sensor rather than the Si7021 but the soldering procedure is identical!
Prepare the header strip:
Cut the strip to length if necessary. It will be easier to
solder if you insert it into a breadboard - long pins down
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 6 of 19
Add the breakout board:
Place the breakout board over the pins so that the short
pins poke through the breakout pads
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 7 of 19
And Solder!
Be sure to solder all pins for reliable electrical contact.
(For tips on soldering, be sure to check out our Guide to
Excellent Soldering
(https://adafru.it/aTk)
).
You're done! Check your solder joints visually and
continue onto the next steps
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 8 of 19
Arduino Code
You can easily wire this breakout to any microcontroller, we'll be using an Arduino. For another kind of microcontroller,
just make sure it has I2C, then port the code - its pretty simple stuff!
Connect Vin to the power supply, 3-5V is fine. Use
the same voltage that the microcontroller logic is
based off of. For most Arduinos, that is 5V
Connect GND to common power/data ground
Connect the SCL pin to the I2C clock SCL pin on
your Arduino. On an UNO & '328 based Arduino,
this is also known as A5, on a Mega it is also
known as digital 21 and on a Leonardo/Micro,
digital 3
Connect the SDA pin to the I2C data SDA pin on
your Arduino. On an UNO & '328 based Arduino,
this is also known as A4, on a Mega it is also
known as digital 20 and on a Leonardo/Micro,
digital 2
https://adafru.it/rAA
https://adafru.it/rAA
The Si7021 has a default I2C address of 0x40 and cannot be changed!
Install Adafruit_Si7021 library
To begin reading sensor data, you will need to install the Adafruit_Si7021 library (code on our github
repository) (https://adafru.it/rAw). It is available from the Arduino library manager so we recommend using that.
From the IDE open up the library manager...
And type in adafruit si7021 to locate the library. Click Install
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 9 of 19
Also install the Adafruit Unified Sensor library in the same way:
We also have a great tutorial on Arduino library installation at:
http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use (https://adafru.it/aYM)
Load Demo
Open up File->Examples->Adafruit_Si7021->si7021 and upload to your Arduino wired up to the sensor
Thats it! Now open up the serial terminal window at 115200 speed to begin the test.
© Adafruit Industries https://learn.adafruit.com/adafruit-si7021-temperature-plus-humidity-sensor Page 10 of 19
Indice
