Grove - 10A DC Current Sensor (ACS725)

The Grove - 10A DC Current Sensor (ACS725) is a high precision DC current sensor based on ACS725. The Allegro™ ACS725 current sensor IC is an economical and precise solution DC current sensing in industrial, automotive, commercial, and communications systems.

The Grove - 10A DC Current Sensor (ACS725) can measure the DC current up to 10A and has a base sensitivity of 264mV/A. This sensor do not support AC current, if you want to measure the AC load please check the:

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

Feature

High-bandwidth 120 kHz analog output for faster response times in control applications
Industry-leading noise performance with greatly improved bandwidth through proprietary amplifier and filter design techniques
1.2 mΩ primary conductor resistance for low power loss and high inrush current withstand capability
Differential Hall sensing rejects common-mode fields
Analog output

Specification

Parameter	Value
Supply voltage	3.3V / 5V
Operating ambient temperature	-40 – 150℃
Storage temperature	- 65°C – 165°C
Working Voltage	<400V
Current sensing range	0 – 10A
Sensitivity	264mV/A(Typ.)
Output interface	Analog
Input interface	Screw terminal

Working Principle

There are two types of current sensing: direct and indirect. Classification is mainly based on the technology used to measure current.

Direct sensing:

Ohm's Law

Indirect seneing:

Faraday's Law of Induction
Magnetic field sensors
Faraday Effect

The Grove - 10A DC Current Sensor (ACS725) uses magnetic field sensors technology. And there are three kinds of Magnetic field sensors technology:

Hall effect
Flux gate sensors
Magneto-resistive current sensor

The Grove - 10A DC Current Sensor (ACS725) is based on the Hall priciple, differential Hall sensing rejects common-mode.

Hardware Overview

Platforms Supported

Arduino	Raspberry Pi

Getting Started

Danger

The human body is forbidden to touch the module during the test, otherwise there is danger of electric shock.

Play With Arduino

Materials required

Seeeduino V4.2	Base Shield	10A DC Current Sensor (ACS725)

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In addition, you can consider our new Seeeduino Lotus M0+, which is equivalent to the combination of Seeeduino V4.2 and Baseshield.

note

1 Please plug the USB cable gently, otherwise you may damage the port. Please use the USB cable with 4 wires inside, the 2 wires cable can't transfer data. If you are not sure about the wire you have, you can click here to buy

2 Each Grove module comes with a Grove cable when you buy. In case you lose the Grove cable, you can click here to buy.

Hardware Connection

Step 1. Connect the Grove - 10A DC Current Sensor(ACS725) to the A0 port of the Base Shield.
Step 2. Connect the positive and negative poles of the circuit to be tested to the corresponding positive and negative poles of the screw terminal.

tip

If you reverse the positive and negative poles, the reading will be reversed. This sensor need calibration before use, so please do not power on the circuit first.

Step 3. Plug Grove - Base Shield into Seeeduino.
Step 4. Connect Seeeduino to PC via a USB cable.

**Figure 4**. *We use the DC Power Supply in this demo, please set the current to 0A or do not power on it at first*

Software

caution

If this is the first time you work with Arduino, we strongly recommend you to see Getting Started with Arduino before the start.

Step 1. Download the Grove Current Sensor Library from Github.
Step 2. In the /example/ folder, you can find the demo code. Here we take the Grove_10A_Current_Sensor for instance. Just click the Grove_10A_Current_Sensor.ino to open the demo. Or you can copy the following code:

#ifdef ARDUINO_SAMD_VARIANT_COMPLIANCE
  #define RefVal 3.3
  #define SERIAL SerialUSB
#else
  #define RefVal 5.0
  #define SERIAL Serial
#endif
//An OLED Display is required here
//use pin A0
#define Pin A0

// Take the average of 500 times
const int averageValue = 500;

long int sensorValue = 0;
float sensitivity = 1000.0 / 264.0; //1000mA per 264mV 


float Vref = 322;   //Vref is zero drift value, you need to change this value to the value you actually measured before using it.
void setup() 
{
  SERIAL.begin(9600);
}

void loop() 
{
  // Read the value 10 times:
  for (int i = 0; i < averageValue; i++)
  {
    sensorValue += analogRead(Pin);

    // wait 2 milliseconds before the next loop
    delay(2);

  }

  sensorValue = sensorValue / averageValue;
 

  // The on-board ADC is 10-bits 
  // Different power supply will lead to different reference sources
  // example: 2^10 = 1024 -> 5V / 1024 ~= 4.88mV
  //          unitValue= 5.0 / 1024.0*1000 ;
  float unitValue= RefVal / 1024.0*1000 ;
  float voltage = unitValue * sensorValue; 

  //When no load,Vref=initialValue
  SERIAL.print("initialValue: ");
  SERIAL.print(voltage);
  SERIAL.println("mV"); 
  
  // Calculate the corresponding current
  float current = (voltage - Vref) * sensitivity;

  // Print display voltage (mV)
  // This voltage is the pin voltage corresponding to the current
  /*
  voltage = unitValue * sensorValue-Vref;
  SERIAL.print(voltage);
  SERIAL.println("mV");
  */

  // Print display current (mA)
  SERIAL.print(current);
  SERIAL.println("mA");
   
  SERIAL.print("\n");

  // Reset the sensorValue for the next reading
  sensorValue = 0;
  // Read it once per second
  delay(1000);
}

Step 3. Upload the demo. If you do not know how to upload the code, please check How to upload code.
Step 4. Open the Serial Monitor of Arduino IDE by click Tool-> Serial Monitor. Or tap the ctrl+shift+m key at the same time. Set the baud rate to 9600.
Step 5. Calibration
When there is no current flowing, the sensor will still have a small output value. We call this value zero offset.

**Figure 5**. *The zero offset of this board is 346.68mV，Converted into current is 93.48mA*

Due to the presence of zero offset, the sensor will also have a reading when there is no current. So we set a parameter Vref to fix it, you can find it in the code block above.

Line 19:

float Vref = 322;  
//Vref is zero drift value, you need to change this value to the value you actually measured before using it.

In the demo code, we set the Vref to 322, however, the zero offset value varies from board to board. As you know, the board we use in this demo is 346.68. So let's modify the Line 21:

float Vref = 346.68;

Then save the code and upload the code again, follow the Step 2. and Step 3. Now let's see：

**Figure 6**. *Now the current zero offset turns to 0mA*

When the current output becomes to 0mA or a small value, you have completed the calibration.

Step 6. Now it's all yours, you can power up the current. Please feel free to use it, remember this is a 10A DC Current Sensor, current cannot exceed 10A!

If you want to know the calculation formula of the result, please refer to the FAQ Q1

Play with Raspberry

Materials required

Raspberry pi	Grove Base Hat for RasPi	10A DC Current Sensor

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Hardware Connection

Step 1. Plug the Grove Base Hat into Raspberry Pi.
Step 2. Connect the Grove - 10A DC Current Sensor(ACS70331) to port A0 of the Base Hat.
Step 3. Connect the positive and negative poles of the circuit to be tested to the corresponding positive and negative poles of the screw terminal.

**Figure 7**. *We use the DC Power Supply in this demo, please set the current to 0A or do not power on it at first*

tip

If you reverse the positive and negative poles, the reading will be reversed. This sensor need calibration before use, so please do not power on the circuit first.

Step 4. Power the Raspberry Pi via the Micro-USB cable.

caution

You can power the Raspberry Pi by computer USB port or DC adapter, however, if you are using the Raspberry pi 3B+, we strongly recommend you to power it by DC adapter, if you use the USB port of the PC, you may damage the Raspberry Pi 3B+.

Software

Step 1. Follow Setting Software to configure the development environment.
Step 2. Download the source file by cloning the grove.py library.

cd ~
git clone https://github.com/Seeed-Studio/grove.py

Step 3. Excute following commands to run the code.

cd grove.py/grove   # to enter the demo file folder
python grove_current_sensor.py 0 10A   # to run the demo program 

Then the terminal will output as following:

pi@raspberrypi:~/grove.py/grove $ python grove_current_sensor.py 0 10A
pin_voltage(mV):
324
current(mA):
8.0
()
pin_voltage(mV):
324
current(mA):
8.0
()
pin_voltage(mV):
323
current(mA):
4.0
()
pin_voltage(mV):
324
current(mA):
8.0
()
pin_voltage(mV):
324
current(mA):
8.0
()
pin_voltage(mV):
324
current(mA):
8.0
()
^CTraceback (most recent call last):
  File "grove_current_sensor.py", line 200, in <module>
    main()
  File "grove_current_sensor.py", line 185, in main
    time.sleep(1)
KeyboardInterrupt

Tap ctrl+c to quit.

note

Please note the second command, There are two parameters after the file name:

0 means the sensor is connected to port A0. If you connect the sensor to port A2, then you need to change this parameter to 2. This parameter has a range of 0-7, but if you use the Grove base hat, you can only use 0/2/4/6 because of the physical limitations of the interface.
10A means the current sensor type is 10A DC

Sensor	Current type	Parameter Value
Grove - 2.5A DC Current Sensor(ACS70331)	DC	2.5A
Grove - ±5A DC/AC Current Sensor (ACS70331)	DC	5A_DC
AC	5A_AC
Grove - 10A DC Current Sensor (ACS725)	DC	10A

This series has three current sensors, the parameter list is as above

note

Please note that the DC current sensor of 10A will have a large error when measuring a small range, so it is recommended that you provide a current of more than 200mA for testing. In addition, the measurement environment will affect the accuracy, such as the supply voltage ripple to be as small as possible.

Step 4 Calibration.
When there is no current flowing, the sensor will still have a small output value. We call this value zero offset. As you can see, in the step 3, the zero offset of this board is 324mV, converted into current is 8mA.
Due to the presence of zero offset, the sensor will also have a reading when there is no current. So we set a parameter Vref to fix it, you can find it in the python grove_current_sensor.py. For the Grove - 10A DC Current Sensor (ACS725), we set the Vref to 322 by default, however the zero offset varies from board to board. That's why we need to do the calibration first.
Check the python code below.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# The MIT License (MIT)
# Copyright (C) 2018  Seeed Technology Co.,Ltd.
#
# This is the library for Grove Base Hat
# which used to connect grove sensors for Raspberry Pi.
'''
This is the code for
    - `Grove - 2.5A DC current sensor  <https://www.seeedstudio.com/Grove-2-5A-DC-Current-Sensor-ACS70331-p-2929.html>`_
    - `Grove - 5A AC/DC current sensor <https://www.seeedstudio.com/Grove-5A-DC-AC-Current-Sensor-ACS70331-p-2928.html>`_
    - `Grove - 10A current sensor      <https://www.seeedstudio.com/Grove-10A-DC-Current-Sensor-ACS725-p-2927.html>`_
Examples:
    .. code-block:: python
        import time
        from grove_current_sensor import Current
        pin = 0
        sensor_type = "2.5A"
        #if use 10A current sensor input: pin = 0 , sensor_type = "10A"
        if (sensor_type == "2.5A"):
            sensitivity = 1000.0 / 800.0
            Vref = 260
        if (sensor_type == "5A_DC"):
            sensitivity = 1000.0 / 200.0
            Vref = 1498
        if (sensor_type == "5A_AC"):
            sensitivity = 1000.0 / 200.0
            Vref = 1498
        if (sensor_type == "10A"):
            sensitivity = 1000.0 / 264.0
            Vref = 322
        averageValue = 500
        ADC = Current()
        while True:
            if(sensor_type == "5A_AC"):
                pin_voltage = ADC.get_nchan_vol_milli_data(pin,averageValue)
                current = ADC.get_nchan_AC_current_data(pin,sensitivity,Vref,averageValue)
            else:
                temp = ADC.get_nchan_current_data(pin,sensitivity,Vref,averageValue)
                current = temp[0]
                pin_voltage = temp[1]
        
            current = round(current)
            print("pin_voltage(mV):")
            print(pin_voltage)
            print("current(mA):")
            print(current)
            print()
            time.sleep(1)
    
'''

import sys
import time
from grove.i2c import Bus

ADC_DEFAULT_IIC_ADDR = 0X04

ADC_CHAN_NUM = 8

REG_RAW_DATA_START = 0X10
REG_VOL_START = 0X20
REG_RTO_START = 0X30

REG_SET_ADDR = 0XC0

__all__ = ['Current','Bus']

class Current():
    '''
    Grove Current Sensor class
    '''

    def __init__(self,bus_num=1,addr=ADC_DEFAULT_IIC_ADDR):
        '''
        Init iic.
        Args: 
            bus_num(int): the bus number;
            addr(int): iic address;
        '''
        self.bus = Bus(bus_num)
        self.addr = addr
  
    def get_nchan_vol_milli_data(self,n,averageValue):
        '''
        Get n chanel data with unit mV.
        :param int n: the adc pin.
        :param int averageValue: Average acquisition frequency.
        Returns: 
            int: voltage value
        '''
        val = 0
        for i in range(averageValue):
            data = self.bus.read_i2c_block_data(self.addr,REG_VOL_START+n,2)
            val += data[1]<<8|data[0]
        val = val / averageValue
        return val

    def get_nchan_current_data(self,n,sensitivity,Vref,averageValue):
        '''
        2.5A/5A DC/10A cunrrent sensor get n chanel data with unit mA.
        :param int n: the adc pin.
        :param float sensitivity: The coefficient by which voltage is converted into current.
        :param int Vref: Initial voltage at no load.
        :param int averageValue: Average acquisition frequency.
        Returns: 
            int: current value
        '''
        val = 0
        for i in range(averageValue):
            data = self.bus.read_i2c_block_data(self.addr,REG_VOL_START+n,2)
            val += data[1]<<8|data[0]
        val = val / averageValue
        currentVal = (val - Vref) * sensitivity
        return currentVal,val

    def get_nchan_AC_current_data(self,n,sensitivity,Vref,averageValue):
        '''
        5A current sensor AC output and get n chanel data with unit mA.
        :param int n: the adc pin.
        :param float sensitivity: The coefficient by which voltage is converted into current.
        :param int Vref: Initial voltage at no load.
        :param int averageValue: Average acquisition frequency.
        Returns: 
            int: current value
        '''
        sensorValue = 0
        for i in range(averageValue):
            data=self.bus.read_i2c_block_data(self.addr,REG_VOL_START+n,2)
            val=data[1]<<8|data[0]
            if(val > sensorValue):
                sensorValue=val
            time.sleep(0.00004)
        currentVal = ((sensorValue - Vref) * sensitivity)*0.707
        return currentVal   

ADC = Current()
def main():
    if(len(sys.argv) == 3):

        pin = int(sys.argv[1])
        sensor_type = sys.argv[2]
        if (pin < 8 and (sensor_type == "2.5A" or sensor_type == "5A_DC" or sensor_type == "5A_AC" or sensor_type == "10A") ):
            if (sensor_type == "2.5A"):
                sensitivity = 1000.0 / 800.0
                Vref = 260
            if (sensor_type == "5A_DC"):
                sensitivity = 1000.0 / 200.0
                Vref = 1498
            if (sensor_type == "5A_AC"):
                sensitivity = 1000.0 / 200.0
                Vref = 1498
            if (sensor_type == "10A"):
                sensitivity = 1000.0 / 264.0
                Vref = 322
            averageValue = 500

            while True:

                if(sensor_type == "5A_AC"):
                    pin_voltage = ADC.get_nchan_vol_milli_data(pin,averageValue)
                    current = ADC.get_nchan_AC_current_data(pin,sensitivity,Vref,averageValue)
                else:
                    temp = ADC.get_nchan_current_data(pin,sensitivity,Vref,averageValue)
                    current = temp[0]
                    pin_voltage = temp[1]

                current = round(current)
                print("pin_voltage(mV):")
                print(pin_voltage)
                print("current(mA):")
                print(current)
                print()
                time.sleep(1)
            
        else:
            print("parameter input error!")
            print("Please enter parameters for example: python grove_current_sensor 0 2.5A")
            print("parameter1: 0-7")
            print("parameter2: 2.5A/5A_DC/5A_AC/10A")
    
    else:
        print("Please enter parameters for example: python grove_current_sensor 0 2.5A")
        print("parameter1: 0-7")
        print("parameter2: 2.5A/5A_DC/5A_AC/10A")
    
    
if __name__ == '__main__':
    main()

You can modify the Vref at line 156 of the code block above:

        if (pin < 8 and (sensor_type == "2.5A" or sensor_type == "5A_DC" or sensor_type == "5A_AC" or sensor_type == "10A") ):
            if (sensor_type == "2.5A"):
                sensitivity = 1000.0 / 800.0
                Vref = 260
            if (sensor_type == "5A_DC"):
                sensitivity = 1000.0 / 200.0
                Vref = 1498
            if (sensor_type == "5A_AC"):
                sensitivity = 1000.0 / 200.0
                Vref = 1498
            if (sensor_type == "10A"):
                sensitivity = 1000.0 / 264.0
                Vref = 322
            averageValue = 500

As you can see, for the 10A Current Sensor the default Vref is 322, and in the Step 3, we can find it when there is no current the zero offset value is 324mV. So let's change it into 324.

            if (sensor_type == "10A"):
                sensitivity = 1000.0 / 264.0
                Vref = 324

Now, let's run this demo again.

pi@raspberrypi:~/grove.py/grove $ python grove_current_sensor.py 0 10A
pin_voltage(mV):
324
current(mA):
0.0
()
pin_voltage(mV):
325
current(mA):
4.0
()
pin_voltage(mV):
324
current(mA):
0.0
()
pin_voltage(mV):
323
current(mA):
-4.0
()
pin_voltage(mV):
324
current(mA):
0.0

Well, better than before, now you can measure the current more accurately 😄

FAQ

Q1# What's the current calculation formula?

A1: If you think the principle part is very complicated, let's put it in a easy way. The current in the circuit to be tested excites the magnetic field, which causes the resistance value of the GMR elements change. And the resistance change in the bridge causes a change in the voltage at the output of the chip. We call the voltage output as V_IOUT.

V_IOUT = Sens × I_p + V_IOUT(Q)

Sens: Sens is the coefficient that converts the current into an output voltage. For this module it is 264mA/V.
I_p: I_p is the current value in the circuit to be tested, Unit mA.
V_IOUT(Q): V_IOUT(Q) is the voltage output when the I_p is 0mA(which means there is no current in the circuit to be tested), Unit mV.

Here comes the current value:

I_p = (V_IOUT - V_IOUT(Q)) / Sens

Now, Let's review the figure 5, we will explain why the current value of the output is not 0 when the actual current value in the circuit to be tested is 0. As you can see in the figure 5, the initialValue is 346.68mV, which is the V_IOUT; the current is 93.48mA, which is the I_p. As for the V_IOUT(Q), it is the Vref we set in the code. In figure 5, it is 265. And the Sens is 264mA/V, which is 264mA/1000mV. Now, just do some math:

{(346.68mV-322mV) / (264mA/1000mV)} = 93.48mA

So, in the figure 6, when we set the Vref to 346.68, the Ip turns to 0mA.

Schematic Online Viewer

Resources

[ZIP] Grove - 10A DC Current Sensor (ACS725) Schematic file
[PDF] ACS725 Datasheet

Tech Support & Product Discussion

Thank you for choosing our products! We are here to provide you with different support to ensure that your experience with our products is as smooth as possible. We offer several communication channels to cater to different preferences and needs.

Feature​

Specification​

Working Principle​

Hardware Overview​

Platforms Supported​

Getting Started​

Play With Arduino​

Hardware Connection​

Software​

Play with Raspberry​

Hardware Connection​

Software​

FAQ​

Schematic Online Viewer​

Resources​

Tech Support & Product Discussion​

Feature

Specification

Working Principle

Hardware Overview

Platforms Supported

Getting Started

Play With Arduino

Hardware Connection

Software

Play with Raspberry

Hardware Connection

Software

FAQ

Schematic Online Viewer

Resources

Tech Support & Product Discussion