Getting back to my IoT projects, I decided to pick up a temperature sensor. While looking through the Adafruit breakout boards, I found they offered nine different digital temperature sensors! This list is in addition to the analog TMP36 temperature sensor, so that’s ten. I needed an Adafruit Temperature Sensor comparison.
With so many options, I quickly found myself getting lost between the various modules. The 10 I found all measured temperature and provided an I2C interface. Except for the MCP9808 board, they all made at least one other type of measurement. The MCP9808 is the cheapest digital temperature sensor breakout that Adafruit offers, and also the most accurate.
I couldn’t find a comparison in my quick search, so I built my own comparison table. Here’s my chart for an Adafruit Temperature Sensor comparison of their breakout boards.
If you want three measurements: Temperature, Humidity, and Barometric pressure the clear winner is the Bosch BME280 board. At about 20 bucks, there isn’t a combination of other breakouts that would work. The tradeoff, however, is that it’s humidity sensor isn’t as accurate as some of the other options.
If you’re interested in any of the boards, just the SKU in the first column to either search their site or go directly there with this URL:
Understanding the Adafruit Temperature Sensor Comparison Chart
While most of my columns are probably obvious, I’ve written some notes about each.
Sensor / Board VCC
These sensors can work on 3.3V systems, while most will work at lower voltages. Adafruit’s breakout boards contain 3.3V regulators and level-shifters for boards not compatible with 5V systems. I broke out the information into two columns. If you’re considering one of these sensors for a project without an Adafruit board, keep in mind, most are designed for 3.3V logic.
Also, in most cases, there are pull-up resistors on the breakout boards. Don’t forget those when you are designing the chip into your own PCB.
Except for the BMP183, all of these modules support I2C. Only two offer user-settable addresses. You’ll want to keep this in mind for whatever other I2C devices your project contains. You may also want to consider one of the SPI alternatives if you suspect an address collision may happen. (Each I2C widget needs its own address.)
There are several Bosch sensors offered by Adafruit. It is pretty easy to get all of the part numbers mixed up. The BMP180 and BMP183 appear to be the same sensor, but different with ad digital interface. Also, don’t confuse the BMP280 and the BME280. The “P” model lacks the humidity sensor.
Using the BME280 on a Raspberry Pi? Check out this BME280 I2C Temperature Sensor in Python Tutorial.
If you read the Adafruit descriptions, any of the sensors that offer a barometric sensor you can also make altitude “measurements.” However, only the MPL3115A2 based board provides a built-in altitude measurement.
After building my Adafruit temperature sensor comparison, I found the clear winner for me. For my data logging project, the Adafruit BME280 breakout’s combination of temperature, humidity, and barometric pressure is perfect. After I get it in my lab, I will let you know how I integrated it with MQTT. Want to see what I’m working on? Subscribe to my RSS or email to find out in a future post. 😉
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Chris offered this weather “proofed” module which is bread-boardable, even though it isn’t a module. –Totally missed that one!
Adafruit also sells the AM2315 (I2C temp & humidity sensor). It’s a nice unit. It’s not a “break-out” version but is easy to setup on a bread board and circuit board (4 pins & two resistor for the I2C pull-ups.
Vilmos sent me some additional information that is great, so wanted share it with you all.
My experiences was the following:
Sensirion sourcing is not easy and so expensive, although the company is really professional and making most of they products for medical industries.
Usually the humidity sensors are used in a moisture and dirt environment, where the PCBs should be coated. If the coating material is covering the hole on the top of the sensor it will not work correctly. Some humidity sensors have the hole on the bottom side of the chip. For example, TI HDC1008, which can improve the dirt resistant and it can be solve the coating problem too.
MCP9808 precision is really good and does not require to calibrate. The chip price is better than Adafruit solution. $1.13 USD at Digikey with free international shipping.
The sourcing of the chip is really important if you want to manufacturing a product. But as I see your BME280 can be buy from more US distributor in a really good price. http://www.findchips.com/search/bme280 The chip price at Future Electronics is 3.78 USD only, therefore the 20 USD adafruit price seems terrible high.
(James Note: This is really true for all of them. For a prototype, Adafruit modules are great. Sure you can buy the chip and get a cheap PCB made and solder them. But at even $20, for a prototype, that’s a great way to go. Once you are ready to source the bare chip for a product, you need to look at a component distributor like Mouser or Digikey.)