ACS712 Current Sensor:Principle,Features and Applications

The invention of electricity has brought about a revolutionary change in human life. We have developed numerous innovative applications of electricity to simplify our daily routines. Nowadays, almost all of our equipment operates on electricity. The flow of charge is referred to as Current. Different devices require varying amounts of current based on their functional needs. Some devices are so sensitive that they can be damaged by a high amount of current. To prevent such situations and to monitor the amount of current needed or being used in an application, measuring current is essential. This is where the Current Sensor becomes crucial. One such sensor is the ACS712 Current Sensor.

 

What is the ACS712 Current Sensor?

 

Current flowing through a conductor causes a voltage drop, a relationship explained by Ohm’s law. In electronic devices, an excess of current beyond its requirement can cause an overload and potentially damage the device.

 

Measuring current is necessary for the proper functioning of devices. While measuring voltage is a passive task and can be done without affecting the system, measuring current is an intrusive task that cannot be detected directly as voltage.

 

To measure current in a circuit, a sensor is necessary. The ACS712 Current Sensor is the sensor that can be used to measure and calculate the amount of current applied to the conductor without affecting the system's performance.

 

The ACS712 Current Sensor is a fully integrated, Hall-effect based linear sensor IC. This IC features a 2.1kV RMS voltage isolation along with a low resistance current conductor.

 

Working Principle of ACS712

 

The ACS712 Current Sensor detects the current in a wire or conductor and generates a signal proportional to the detected current, either in the form of analog voltage or digital output.

 

Current sensing is accomplished in two ways: Direct sensing and Indirect Sensing. In Direct sensing, Ohm’s law is used to measure the voltage drop that occurs in a wire when current flows through it.

 

A current-carrying conductor also produces a magnetic field in its surroundings. In Indirect Sensing, the current is measured by calculating this magnetic field using either Faraday’s law or Ampere’s law. In this method, a Transformer, Hall effect sensor, or fiber optic current sensor is used to sense the magnetic field.

 

The ACS712 Current Sensor uses the Indirect Sensing method to calculate current. To sense current, a linear, low-offset Hall sensor circuit is used in this IC. This sensor is located on the surface of the IC on a copper conduction path. When current flows through this copper conduction path, it generates a magnetic field, which is sensed by the Hall effect sensor. The Hall sensor then generates a voltage proportional to the sensed magnetic field, which is used to measure the current.

 

The proximity of the magnetic signal to the Hall sensor determines the accuracy of the device. The closer the magnetic signal, the higher the accuracy. The ACS712 Current Sensor is available as a small, surface-mount SOIC8 package. In this IC, current flows from Pin-1 and Pin-2 to Pin-3 and Pin-4, forming the conduction path where the current is sensed. Implementing this IC is very easy.

 

The ACS712 can be used in applications requiring electrical isolation since the terminals of the conduction path are electrically isolated from the IC leads. Therefore, this IC doesn’t need any additional isolation techniques. It requires a supply voltage of 5V, and its output voltage is proportional to AC or DC current. The ACS712 has nearly zero magnetic hysteresis.

 

Pins 1 to 4 form the conduction path, Pin-5 is the signal ground pin, Pin-6 is the FILTER pin used by an external capacitor to set the bandwidth, Pin-7 is the analog output pin, and Pin-8 is the power supply pin.

 

Features of ACS712 Current Sensor

 

The features of the ACS712 include:

 

• 80kHz bandwidth
• 66 to 185 mV/A output sensitivity
• Low-noise analog signal path
• Device bandwidth set via the new FILTER pin
• 1.2 mΩ internal conductor resistance
• Total output error of 1.5% at TA = 25°C
• Stable output offset voltage
• Near zero magnetic hysteresis

 

How does the ACS712 Current Sensor work?

 

Now that we have an idea of what the ACS712 is capable of, let’s look at its working principle. The ACS712 uses indirect sensing to measure current.

 

In direct sensing, Ohm’s law is applied to measure the voltage drop when current flows through a conductor.

 

Here’s how the ACS712 works (Simplified):

 

• Current flows through the onboard Hall sensor circuit in its IC.
• The Hall effect sensor detects the incoming current by sensing its generated magnetic field.
• The Hall effect sensor then generates a voltage proportional to the magnetic field, which is used to measure the amount of current.

 

 

Applications of ACS712 Current Sensor

 

The ACS712 Current Sensor can detect both AC and DC current, making it suitable for a wide range of applications. It is used in peak detection circuits, circuits to increase gain, rectification applications for AtoD converters, and overcurrent fault latches, among others. The filter pin provided by this IC helps eliminate the attenuation effect in resistor divider circuits.

 

The ACS712 is utilized in many industrial, commercial, and communication applications, including automotive applications. Typical uses include motor control circuits, load detection and management, SMPS, and overcurrent fault protection circuits.

 

Here are the common applications:

 

• - Motor speed control in motor control circuits
• - Electrical load detection and management
• - Switched-mode power supplies (SMPS)
• Protection against over-current

 

ACS712 Alternatives

 

Grove – 10A DC Current Sensor (ACS725)

 

Some users do not recommend the ACS712 as their current sensor option due to its low sensitivity and poor linearity. As an alternative, we recommend the Grove – 10A DC Current Sensor, based on the ACS725!

 

This DC current sensor module, based on the ACS725, offers an economical and precise solution for your current sensing needs, capable of measuring up to 10A of DC current with a base sensitivity of 264mV/A!

 

When comparing the ACS712 to the Grove – 10A DC Current Sensor (ACS725), the latter has the following performance advantages:

 

• Higher bandwidth: 120kHz compared to the 80kHz of the ACS712
• Higher sensitivity: 264mV/A compared to 66–185mV/A of the ACS712
• Grove interface: Easy plug-and-play pairing with your Arduino/Raspberry Pi board, eliminating the need for soldering and using breadboards

 

Grove – ±5A DC/AC Current Sensor (ACS70331)

 

If you’re looking for a current sensor that supports both AC and DC while retaining performance advantages over the ACS712, the Grove – ±5A DC/AC Current Sensor (ACS70331) is your pick!

 

Based on Allegro’s high sensitivity current sensor IC, the ACS70331EESATR-005B3, it’s suitable for <5A current sensing applications, with a base sensitivity of 200mV/A.

 

Its features include:

 

• 1 MHz bandwidth with response time <550 ns
• Low noise: 8 mA(rms) at 1 MHz
• 1.1 mΩ primary conductor resistance, resulting in low power loss
• High DC PSRR, enabling use with low accuracy power supplies or batteries (3 to 4.5 V operation)

 

ACS712 Current Sensor Arduino Guide

 

The ACS712 current sensor can be connected to your Arduino board through a series of jumper wire connections based on its pinout. At Seeed, we understand the complications and complexity of doing so. Therefore, we provide a tutorial for our Grove – ±5A DC/AC Current Sensor (ACS70331) to showcase the simplicity of our Grove plug-and-play system!

 

Here’s what you need for today’s tutorial:

 

• Seeeduino, Seeed’s very own Arduino board, built with relative benefits over the original
• If you do not wish to purchase a Seeeduino, this tutorial is still applicable for the following Arduino boards: Arduino UNO, Arduino Mega, Arduino Leonardo, Arduino 101, Arduino Due

 

Hardware Assembly:

 

• Step 1: Connect the Grove – ±5A DC/AC Current Sensor (ACS70331) to port A0 of the Grove – Base Shield.
• Step 2: Connect the positive and negative terminals of the circuit to be tested to the corresponding positive and negative terminals of the screw terminal.
• Step 3: Plug the Grove – Base Shield into the Seeeduino.
• Step 4: Connect the Seeeduino to the PC via a USB cable.

 

Please note that the above hardware connection is performed using a DC power supply. Ensure to set the current to 0A or keep it powered off initially.

 

Summary:

 

Although the ACS712 is a popular choice for current sensor modules in Arduino applications, its performance disadvantages compared to our alternatives here at Seeed should be considered!

 

If you’re starting out with current sensing using an AC/DC current sensor, we recommend our featured products:

 

For DC current sensing only: Grove – 10A DC Current Sensor (ACS725)

For both AC/DC current sensing: Grove – ±5A DC/AC Current Sensor (ACS70331)

 

 

This IC can measure current for high voltage loads operating at 230V AC mains and can be easily interfaced with the ADC of a microcontroller to read the values. What would be the output voltage provided by the ACS712 when a DC load current is applied to it?