Field Installation Doc · Wiring & Pinmap

Temp/Humidity Node — Site 1 / Server Room

A measurement node connecting the SHT30 temperature/humidity sensor to the Raspberry Pi (Pi-B) over I2C (bus 1, address 0x44). This node only reports readings to the server every 5 minutes; high/low temperature and high/low humidity threshold decisions and SMS dispatch are handled by the server.

Raspberry Pi 4 Model B BCM2711 Raspberry Pi OS Bookworm 64-bit Sensirion SHT30 (Hanjin Data P4422-3) I2C bus 1 addr 0x44 sensor_id=2 Report interval 5 min

240-Pin Header Pinmap Diagram Used pins highlighted · others in gray

3.3V power — pin 1 I2C SDA/SCL — pins 3·5 GND (used) — pin 6 Alt GND (optional) — 9·14·20·25·30·34·39 Unused pins

The pin numbers and signals in this diagram match the standard Raspberry Pi 4 Model B (BCM2711) 40-pin header layout.

3Pinmap Table SHT30 → 40-pin header

Signal	BCM	Phys pin	Notes
3.3V power (VCC)	—	1	★ Must be 3.3V — do NOT connect 5V (pins 2·4)
I2C data (SDA)	GPIO2 / SDA1	3	4.7kΩ pull-up → 3.3V (omit if built into module)
I2C clock (SCL)	GPIO3 / SCL1	5	4.7kΩ pull-up → 3.3V (omit if built into module)
Ground (GND)	—	6	Alt GND available: 9 · 14 · 20 · 25 · 30 · 34 · 39
Address select (ADDR)	—	GND	ADDR → GND ⇒ 0x44 (selected) · ADDR → VDD ⇒ 0x45

4Wiring Schematic sensor ↔ header ↔ pull-up resistors

Pull-up resistors R1·R2 (4.7kΩ ×2) connect to the 3.3V rail. Omit if built into the SHT30 module. The half-circle (hop) on the SDA line only marks a wire crossing — it is not an electrical connection.

5Electrical Design · Cautions

Critical Warning — On the Pi it MUST be 3.3V

Connect the SHT30's VCC to physical pin 1 (3.3V). Do NOT connect 5V (pins 2·4) on the Pi — the SHT30 module itself tolerates 2.4–5.5V, but powering it with 5V pulls the SDA/SCL lines up to 5V as well, which damages the 3.3V-only Pi GPIO. Double-check the pin numbers before wiring.

I2C pull-ups: Connect a 4.7kΩ pull-up resistor on each of SDA and SCL to 3.3V. Can be omitted if built into the sensor module.
Address setting: ADDR → GND gives 0x44 (default), ADDR → VDD gives 0x45. Must match the I2C_ADDR value in config.py.
I2C bus: Uses bus 1. I2C must be enabled after boot (raspi-config or dtparam=i2c_arm=on).
Wiring length: Short cables are recommended for I2C. Long cables may cause communication errors or require adjusting the pull-up values.
Role split: This node only reports readings to the server every 5 minutes. High/low temperature and high/low humidity threshold decisions and SMS dispatch are done by the server.
Config file: raspberry_pi4_sht30/config.py (I2C_BUS=1, I2C_ADDR=0x44). Per-device values are overridden in config_local.py.

# Check I2C connection (OK if 0x44 appears in the grid) $ i2cdetect -y 1 0 1 2 3 4 5 6 7 8 9 a b c d e f 40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --

6Installation Checklist

Do wiring work with power disconnected (no hot-plugging)
Connect VCC → physical pin 1 (3.3V) — re-verify it is NOT a 5V pin (2·4)
Connect GND → physical pin 6 (or 9·14·20·25·30·34·39 for alt GND)
Connect SDA → pin 3 (GPIO2), SCL → pin 5 (GPIO3)
Connect 4.7kΩ ×2 pull-up resistors from SDA·SCL → 3.3V (omit if built into module)
Verify ADDR → GND (address 0x44 selected)
Re-check all wiring, then power up the Pi
Verify I2C is enabled (raspi-config / dtparam=i2c_arm=on)
Run i2cdetect -y 1 → confirm 0x44 is shown
Verify I2C_BUS=1, I2C_ADDR=0x44 in config.py / config_local.py
Check measurement log and server reception (5-min reporting OK)