Hardware Overview
SFA40 Formaldehyde Sensor
The SFA40 formaldehyde sensor from Sensirion is a compact electrochemical indoor gas sensor designed to measure concentrations of formaldehyde gas. It has very low cross-sensitivity with similar, common indoor gases like ethanol and nitrogen dioxide. It's intended to measure indoor gas concentrations over long periods of time and has a long-term drift of <5ppb (or <5% of the measured value, whichever is larger) per year. The sensor includes humidity and temperature sensing to compensate the formaldehyde signal. Each SFA40 has a unique 48-bit serial number and self-test for verifying the sensor's electrical connections.
The SFA40 provides a calibrated digital output with an accuracy of ±20ppb (parts per billion) or ±20% of the total measurement range of 0 to 2000ppb. The sensor does require a 10 minute calibration period on power up. The SFA40 accepts a supply voltage 1.6 to 3.6V (3.3V over Qwiic) and draws an average of 80µA during measurement with a max of 6mA. While idle it draws an average of 60µA. For a complete overview of the SFA40, take a look at the datasheet
Connectors
Qwiic Connectors
The board has a pair of Qwiic connectors to make it easy to integrate into a Qwiic circuit. These connect to the SFA40's I2C signals along with 3.3V and ground to power the board and communicate with the SFA40.
Plated Through-Hole (PTH) Header
The board also routes the same signals as the Qwiic connectors (SDA, SCL, 3.3V and Ground) to a 0.1"-spaced plated through-hole header for users who prefer a soldered connection.
LED
The lone LED on this breakout is a red power status LED.
Solder Jumpers
The board has two solder jumpers labeled LED and I2C. The LED jumper completes the power LED circuit and is CLOSED by default. Open this jumper to disable the power LED. The I2C jumper is a three-way jumper that pulls the SFA40's SDA and SCL lines to 3.3V through a pair of 2.2kΩ resistors and is CLOSED by default. Completely open this jumper to disable pullups on the I2C bus if necessary.
Board Dimensions
This breakout matches the Qwiic standard and measures 1" x 1" (22.5mm x 22.5mm) and has four mounting holes that fit a 4-40 screw.