Supported Sensor Types
LoopString supports a wide range of sensors across multiple communication protocols:
1-Wire Sensors
- DS18B20 — Waterproof temperature probe, most popular for environmental monitoring
- Connect to GPIO 4 (default 1-Wire bus) with a 4.7k ohm pull-up resistor
- Multiple DS18B20 sensors can share the same 1-Wire bus
I2C Sensors
- BME280 — Temperature, humidity, and barometric pressure
- BH1750 — Light intensity (lux)
- Connect to SDA (GPIO 2) and SCL (GPIO 3) with 3.3V power
- Each I2C sensor needs a unique address on the bus
UART Sensors
- MH-Z19 — CO2 concentration (NDIR)
- Atlas Scientific EZO — pH, EC (conductivity), dissolved oxygen
- Connect to the Pi UART pins (TX/RX) — one UART sensor per serial port unless using a multiplexer
Analog Sensors (via ADC)
- Any analog sensor can be used with an ADC (analog-to-digital converter) like the ADS1115
- The ADC connects via I2C and provides 4 analog input channels
- Supports configurable signal ranges and polynomial calibration
System Sensors
- CPU Temperature — Built-in Pi thermal sensor
- Memory Usage — Available and used RAM
- Disk Usage — SD card space
- Uptime — Time since last boot
These are available as parts in the Configurator without any wiring.
Wiring Best Practices
- Use appropriate pull-up resistors for 1-Wire and I2C buses
- Keep wire runs short — under 3 meters for I2C, under 20 meters for 1-Wire with shielded cable
- Use 3.3V logic — the Pi GPIO pins are 3.3V and are not 5V tolerant
- Add decoupling capacitors (100nF) near sensor power pins for stable readings
- Test one sensor at a time before adding more to isolate wiring issues
Verifying Sensor Data
Once a sensor is wired and configured in the Configurator:
- Open your Dashboard
- Navigate to the room where the sensor is assigned
- Look for the SensorStat card — it shows the current reading, sparkline trend, and alarm status
- If the card shows "No data", check wiring and the Sensor Not Reporting guide
Sensor Calibration
For sensors that need calibration (pH, EC, analog sensors):
- Open the sensor card on the dashboard
- Click the calibration icon
- Choose a calibration mode:
- Offset — Simple zero-point adjustment
- Linear — Two-point calibration for slope and offset
- Follow the on-screen wizard with your reference solutions
- The calibration applies in real time with a live preview
Next Steps
- Deploying Your First Flow to start reading sensors automatically
- Configurator Overview to learn about the visual flow editor