MQ131 ozone sensor breakout: power supply and pull-up configuration with ESP8266

TECHNICAL SUPPORT Sensors & Modules
1

Customer:

I plan to use the Ozone sensor MQ131 breakout with easyC with a Wemos D1 mini (ESP8266) powered via USB. Should I use the 5V pin or the 3.3V pin on the D1 mini for VCC on the easyC port? If the board is intended for 5V VCC, is it OK to power it directly from the D1 mini’s 5V (USB) while keeping I²C at 3.3V on SDA/SCL? Do I need to set the pull-up jumper to 3.3V (JP2) and leave 5V pull-ups (JP1) open? If 3.3V VCC is also supported, what current does the board require? Would powering it from the D1 mini’s 3.3V regulator be sufficient, or do you recommend a separate 3.3V supply? My intended wiring is: 5V (D1 mini) → VCC (sensor), GND ↔ GND, D2 (SDA) → SDA, D1 (SCL) → SCL. It would also help to know the typical heater current / total power consumption and any recommendations for decoupling when powered from USB.

Originally submitted via email support on 14 August 2025. Migrated to the forum for community visibility.

2

Soldered Support:

For the MQ131 breakout with Wemos D1 mini (ESP8266) using easyC:

Powering:

  • Connect 3.3V from D1 mini → VCC on sensor
  • GND → GND
  • D2 (SDA) → SDA
  • D1 (SCL) → SCL

Pull-ups:

  • Close JP2 (3.3V pull-up) → required for safe I²C with ESP8266
  • Leave JP1 (5V pull-up) open

Typical consumption:

  • Heater: 30–50 mA typical, up to ~100 mA peak
  • Logic: ~2–5 mA
  • Total <100 mA

The D1 mini’s 3.3V regulator can usually supply enough current for the sensor plus WiFi. If you notice instability (resets, brown-outs), consider adding a small decoupling capacitor (100 nF + 10 µF) across VCC/GND near the sensor.

Power the MQ131 through 3.3V when using easyC, and keep I²C pull-ups at 3.3V. Please note: we don’t have a D1 mini on hand to test directly - these numbers are estimates based on the MQ131 datasheet and practice, so take them as guidance rather than exact measurements.

Attachment omitted in migration: image001.jpg