SH22 Electrochemical Formaldehyde (CH2O) Sensor Module 0–5 PPM UART
SH22 Electrochemical Formaldehyde (CH2O) Sensor Module 0–5 PPM UART
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Short Product Description
Short Product Description
The SH22 is a compact electrochemical gas sensor module designed to measure formaldehyde (CH₂O / HCHO) concentrations from 0 to 5 PPM. Operating on a 3.7V to 5.5V DC supply, it outputs calibrated digital readings at 9600 bps via a 3.3V TTL UART interface. With a resolution of ≤0.010 mg/m³ and a 23 x 25.5mm footprint, it is built for Arduino, ESP32, and Raspberry Pi indoor air quality monitors, smart home purifiers, and post-renovation testing devices.
Key Features
Key Features
- 0–5 PPM Measurement Range: Detects trace indoor formaldehyde concentrations down to ≤0.010 mg/m³ resolution for post-renovation monitoring.
- Factory-Calibrated UART Output: Streams 9600 bps serial data (active 1s interval or Q&A query mode) without needing external ADC circuitry.
- 3.7V–5.5V Wide Supply: Runs directly from a 1S lithium battery, 5V USB rail, or microcontroller 5V pin while using 3.3V UART logic.
- Compact 23 × 25.5mm Footprint: Fits easily inside custom 3D-printed air quality monitors, desktop stations, and air purifiers.
- Included 7-Pin Harness: Ships with a matching 7-pin 1.25mm pitch ribbon cable for solderless connection on Pins 3–6.
Full Product Description
Full Product Description
Accurate Formaldehyde Detection for Air Quality Projects
The SH22 sensor module uses an electrochemical sensing cell to measure indoor formaldehyde concentrations from 0 to 5 PPM with a resolution of ≤0.010 mg/m³. Unlike basic semiconductor gas sensors that require complex analog calibration, the SH22 outputs pre-processed digital data directly over a 9600 bps UART serial interface. It supports both default 1-second active reporting (in ppb) and on-demand Q&A polling (returning both µg/m³ and ppb), making integration straightforward on Arduino, ESP32, or STM32 boards.
Compact 3.3V UART Integration and Wiring
Powered by 3.7V to 5.5V DC through its 7-pin 1.25mm connector, the SH22 communicates using 3.3V logic levels on its RXD (Pin 5) and TXD (Pin 6) lines. Its 23 x 25.5mm PCB includes four mounting holes and comes with a 7-pin ribbon cable for quick connection to custom carrier boards or microcontroller prototypes. Allow up to 3 minutes for sensor warm-up upon initial power-on, with typical response and recovery times within 60 seconds.
Technician Tip
Pay close attention to the 3.3V UART logic level and cross-sensitivity behavior before deploying the SH22. Our technicians at Sun Cheong advise using a bidirectional logic level shifter if connecting Pin 5 (RXD) to a 5V Arduino Uno, whereas 3.3V boards like ESP32 or Raspberry Pi can connect directly—even when powering Vin (Pin 4) at 5V. Also, avoid testing near alcohol wipes, hand sanitizers, or perfume, as 100 PPM of alcohol produces an equivalent reading of 40.6 PPM on this electrochemical cell; store the module in clean air (0–25°C) and avoid touching or puncturing the white top sensing membrane.
Technical Specifications
Technical Specifications
- Model: SH22
- Target Gas: Formaldehyde (CH₂O / HCHO)
- Detection Principle: Electrochemical
- Measurement Range: 0 – 5 PPM
- Resolution: ≤ 0.010 mg/m³
- Output Interface: UART (3.3V TTL logic, 9600 bps, 8N1)
- Operating Voltage: 3.7V – 5.5V DC (Pin 4: Vin, Pin 3: GND)
- Warm-Up Time: ≤ 3 minutes
- Response / Recovery Time: ≤ 60 seconds / ≤ 60 seconds
- Operating Environment: -20°C to 50°C, 15% to 90% RH (Storage: 0°C to 25°C)
- Expected Lifespan: 2 years (general air 0–35°C) / 5 years (clean air 0–35°C)
- Dimensions: 23mm x 25.5mm x 7mm (±1.2mm height)
- Connector & Pinout: 7-Pin 1.25mm Pitch (1: NC, 2: NC, 3: GND, 4: Vin, 5: RXD, 6: TXD, 7: NC)
- Operating Current / Brand / GTIN: Not specified — confirm manually
Delivery Options
Delivery Options
- Local delivery within Hong Kong and in-store pickup.
- Free shipping for orders of HK$400 or above; HK$35 shipping fee for orders below HK$400.
- Shipped by SF Express, usually dispatched the same day for orders confirmed before 6:00 PM (Mon–Sat).
- Estimated delivery time: 1–3 business days after dispatch (Hong Kong).
- In-store pickup details (location and time) will be confirmed by email or phone message.
- Delivery times are estimates and may be affected by weather or unforeseen circumstances.
FAQ Section
FAQ Section
- Can I connect the SH22 formaldehyde sensor directly to a 5V Arduino Uno?You can power Pin 4 (Vin) from 5V, but you should use a 3.3V-to-5V logic level shifter on Pin 5 (RXD) because the UART interface operates at 3.3V logic levels.
- How does the SH22 electrochemical sensor compare to a cheaper MQ-series gas sensor?The SH22 provides selective formaldehyde measurement from 0 to 5 PPM with digital UART output in ppb and µg/m³, whereas MQ sensors only give rough analog readings sensitive to general VOCs and heat.
- Why does my SH22 reading spike sharply when someone uses hand sanitizer or alcohol nearby?Electrochemical formaldehyde cells exhibit cross-sensitivity to alcohol, where 100 PPM of ethanol can trigger an equivalent reading of roughly 40.6 PPM.
- Can I pick up the SH22 sensor and matching logic level shifters at your Sham Shui Po store?Yes, you can pick up the SH22 module along with ESP32 boards, jumper wires, and logic level shifters at our Sham Shui Po shop (新昌電腦有限公司).
- What baud rate and serial mode does the SH22 use by default?The SH22 defaults to 9600 bps (8 data bits, 1 stop bit, no parity) in active upload mode, sending a 9-byte concentration frame every 1 second.
Target Users / Applications
Target Users / Applications
- Homeowners and interior contractors building DIY post-renovation formaldehyde air quality monitors using ESP32 or Home Assistant (ESPHome).
- University engineering students and STEM labs developing multi-parameter indoor air quality stations.
- Smart home makers integrating UART gas sensing into automated ventilation fans or DIY air purifiers.
