The ACS712 20A is a hall-effect-based linear current sensor designed for measuring high-current AC or DC loads. It provides a reliable and low-cost solution for power monitoring and control. By utilizing the Hall effect, the module ensures the high-current path is electrically isolated from your sensitive microcontroller electronics (like Arduino or ESP32), significantly increasing system safety.

Specifications

• Supply Voltage (VCC): 4.5V – 5.5V DC
• Measurement Range: -20A to +20A (Bi-directional)
• Sensitivity: 100mV/A
• Output Voltage at 0A: VCC / 2 (Typically 2.5V)
• Internal Conductor Resistance: 1.2 MOhm
• Isolation Voltage: 2.1 kVRMS
• Operating Temperature: -40C to +85C

Working Principle

As current passes through the copper conduction path inside the module, it generates a magnetic field. The integrated Hall-effect sensor detects this field and converts it into a voltage that is linearly proportional to the input current. Because the sensing is magnetic rather than direct, your measurement circuit remains isolated from the load circuit.

Features

• Bi-directional Measurement: Capable of measuring current in both directions. At 5V VCC, the output sits at 2.5V for 0A. It increases toward 5V for positive current (+20A = 4.5V) and decreases toward 0V for negative current (-20A = 0.5V).
• Galvanic Isolation: The 2.1 kVRMS isolation allows the sensor to be used in high-side applications safely, preventing high-voltage spikes from reaching the microcontroller.
• Low Power Loss: The extremely low resistance (1.2 MOhm of the internal copper path means the sensor introduces almost no voltage drop to your load, even at the full 20A capacity.
• High Bandwidth: Features an 80kHz bandwidth, allowing it to accurately sense fast-switching currents in motor controllers and SMPS.
• Stable Analog Output: The output is a simple DC voltage that maps directly to your MCU's Analog-to-Digital Converter (ADC).

Pin Configuration

• Input (Screw Terminals):
  • Terminals: Connect in series with the positive or negative wire of the load you are measuring.
• Output (3-Pin Header):
  • VCC: 5V Power Supply.
  • OUT: Analog Signal Output.
  • GND: Ground.

Common Applications

• Motor Speed Control: Monitoring the current draw of DC motors to prevent stalling or burnout.
• Solar Power Monitoring: Measuring the high-current output of large solar arrays.
• Inverter Systems: Tracking current in DC-to-AC power conversion.
• Industrial Automation: Detecting over-current faults in heavy-duty machinery.

Usage Tips

• Noise Management: If the reading is jumpy, add a small 0.1uF capacitor between the OUT pin and GND to filter out high-frequency noise.
• Zero-Current Calibration: Because the sensor is sensitive to external magnetic fields, it is best to take a reading at start-up (with the load off) to determine your specific 0A voltage baseline.
• Sensitivity Math: To calculate current in Amps for the 20A model: Current (A) = [Output Voltage (V) - (VCC / 2)] / 0.100