Current Sensors

A current sensor shows what your project actually draws. That tells you how long a battery will last, whether a motor has stalled, and how much energy an appliance uses.

  • The INA219 measures current, bus voltage and power over I2C. It is accurate enough to keep a running mAh total on an ESP32 with a small OLED.
  • The INA3221 watches three channels at once.
  • Hall-effect sensors such as the ACS712 (5A, 20A and 30A versions) measure larger currents. Our builds use the ACS712 for AC current.
  • For a whole home, a non-invasive clamp sensor with a burden circuit reads mains current without cutting any wires.

How to choose:

  • Pick an INA219 or INA3221 for low-voltage DC projects where you also want voltage and power.
  • Pick an ACS-series sensor for higher currents.
  • Pick a clamp sensor for mains energy monitoring.

Accuracy depends on the shunt resistor. The current flows through this small, precise resistor, and the sensor reads the voltage across it, so pick a range that matches your load.

Mains measurement carries real risk. Clamp sensors avoid touching live wiring; never open live mains circuits.

Frequently asked questions

Why measure current in a project?

To estimate battery life, catch a stalled or jammed motor, and track energy use.

INA219 or ACS712?

The INA219 for precise low-voltage DC with voltage and power. The ACS712 for larger currents, including AC.

What does the shunt resistor do?

Current passes through it, and the sensor reads the small voltage across it. Its value sets range and accuracy.

How do I measure home energy safely?

Use a non-invasive clamp sensor around one wire, so you never touch live mains.

Guides

Reference pages on soldr.ai

More guides on soldr.ai

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