The Adafruit PCT2075 Temperature Sensor is a 'code compatible' drop-in replacement for a very common I2C temperature sensor, the LM75. Compared to the LM75, however, the 11-bit ADC in the PCT2075 provides more precise measurements when compared to the LM75's 9-bit ADC. Additionally, because the PCT2075 allows the address pins to work in three states (high, low, floating), you can have 27 PCT2075s on the same bus as opposed to only 8 for the LM75. Now you can finally measure the individual temperatures of the tentacles of three octopuses instead of just one!
Otherwise, the two sensors are the same. The PCT2075 will report temperature and allow you to set a high-temperature threshold that the sensor will compare to the current temperature and raise an alert when the current temperature exceeds the threshold. There are also a few (metaphorical) knobs to twist to change the alerting and measurement behavior.
As with all Adafruit breakouts, we've done the work to make this handy temperature helper super easy to use. We've put it on a breakout board with the required support circuitry and connectors to make it easy to work with, and is now a trend we've added SparkFun Qwiic compatible STEMMA QT JST SH connectors that allow you to get going without needing to solder. Just use a STEMMA QT adapter cable, plug it into your favorite micro or Blinka-supported SBC and you're ready to rock!
To know more about STEMMA QT, watch this video:
The PCT2075 is a handy and inexpensive temperature sensor that does one thing well. Try adding one to your project and have it keep an eye on the temperature and let you know when things get hot - or cold!
Pinouts:
- Power Pins
The sensor on the breakout requires between a 2.7V and 5.5V, and can be easily used with most microcontrollers from an Arduino to a Feather or something else.- Vcc - this is the power pin. 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
- GND - common ground for power and logic
- I2C Logic Pins
- SCL - this is the I2C clock pin, connect to your microcontroller's I2C clock line.
- SDA - this is the I2C data pin, connect to your microcontroller's I2C data line
- STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT connectors or to other things with various associated accessories
- Other Pins
- INT -This is the interrupt pin. You can setup the PCT2075 to activate this pin when a temperature threshold is reached or exceeded.
- A0, A1, A2 - I2C Address pins. See the "I2C Address Selection" section below
- I2C Address Selection
One of the improvements that the PCT2075 has over the LM75 that it can replace is the ability to have three times the number of I2C addresses. Interestingly, they achieve this by allowing the three address pins A0, A1, and A2 be in one of three states, low (0), high(1), or floating(F). This means that the are 33 (27) possible addresses. Attach the address pin to ground for low, the logic level of your device for hight, or leave the pin unconnected for floating.
We leave all three address pins floating on the breakout for maximum configurability. This means that the default address for the breakout is 0x37.
For a more permanent address selection, you can use the solder jumpers on the back of the breakout board to connect the address pins to GND or VCC.
All you need to do is bridge the "Float" pad to either the VCC or GND pad for one or more of the address pins. In the picture above if you bridged the solder pads that are circled, you would pull A0 high to VCC and A1 low to GND. Referring to the table above this would set the address of the breakout to 0x72
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