Grove - Electricity Sensor

Introduction

The Electricity sensor module is a member of Grove. It is based on the TA12-200 current transformer which can transform the large AC into small amplitude. You can use it to test large alternating current up to 5A.

Features

• Grove compatible interface
• Maximum 5A input
• High accuracy
• Small size

Application Ideas

• Alternating current measurement
• Device condition monitoring

Specification

Key Specification

Items	Min
PCB Size	2.0cm*4.0cm
Interface	2.0mm pitch pin header
IO Structure	SIG,NC,NC,GND
RoHS	YES

Electronic Characteristics

Items	Min	Norm	Max	Unit
Transformation ratio	-	2000:1	-	-
Input Current	0	-	5	A
Output Current	0	-	2.5	mA
Sampling Resistance	-	800	-	Ω
Sampling Voltage	0	-	2	V
Working Frequency	20	-	20K	HZ
Nonlinear scale	-	-	0.2%	-
Phase Shift	-	-	5’	-
Operating Temperature	-55	-	85	℃
Dielectric strength	-	6	-	KVAC/1min

Platforms Supported

Usage

With Arduino

The following sketch demonstrates a simple application of measuring the amplitude of the alternating voltage. The SIG pin will output a alternating voltage based on the alternating current being measured. You can measure the value using ADC.

• Connect the module to the analog A0 of Grove - Base board.
• Put the alternating current wire through the hole of the current transformer.

• Copy and paste code below to a new Arduino sketch.

    /****************************************************************************/  
    //  Function: Measure the amplitude current of the alternating current and 
    //            the effective current of the sinusoidal alternating current.
    //  Hardware: Grove - Electricity Sensor        
    //  Date:    Jan 19,2013
    //  by www.seeedstudio.com
    #define ELECTRICITY_SENSOR A0 // Analog input pin that sensor is attached to

    float amplitude_current;               //amplitude current
    float effective_value;       //effective current 

    void setup() 
    {
        Serial.begin(9600); 
        pins_init();
    }
    void loop() 
    {
        int sensor_max;
        sensor_max = getMaxValue();
        Serial.print("sensor_max = ");
        Serial.println(sensor_max);
        //the VCC on the Grove interface of the sensor is 5v
        amplitude_current=(float)sensor_max/1024*5/800*2000000;
        effective_value=amplitude_current/1.414;//minimum_current=1/1024*5/800*2000000/1.414=8.6(mA) 
                            //Only for sinusoidal alternating current
        Serial.println("The amplitude of the current is(in mA)");
        Serial.println(amplitude_current,1);//Only one number after the decimal point
        Serial.println("The effective value of the current is(in mA)");
        Serial.println(effective_value,1);
    }
    void pins_init()
    {
        pinMode(ELECTRICITY_SENSOR, INPUT);
    }
    /*Function: Sample for 1000ms and get the maximum value from the SIG pin*/
    int getMaxValue()
    {
        int sensorValue;             //value read from the sensor
        int sensorMax = 0;
        uint32_t start_time = millis();
        while((millis()-start_time) < 1000)//sample for 1000ms
        {
            sensorValue = analogRead(ELECTRICITY_SENSOR);
            if (sensorValue > sensorMax) 
            {
                /*record the maximum sensor value*/
                sensorMax = sensorValue;
            }
        }
        return sensorMax;
    }

• Upload the code.

• Open the serial monitor, The results is as follows：

With Raspberry Pi

1.You should have got a raspberry pi and a grovepi or grovepi+.

2.You should have completed configuring the development enviroment, otherwise follow here.

3.Connection

• Plug the sensor to grovepi socket A0 by using a grove cable.

4.Navigate to the demos’ directory:

   cd yourpath/GrovePi/Software/Python/

• To see the code

    nano grove_electricity_sensor.py   # "Ctrl+x" to exit #

    import time
    import grovepi

    # Connect the Grove Electricity Sensor to analog port A0
    # SIG,NC,NC,GND
    sensor = 0

    grovepi.pinMode(sensor,"INPUT")

    # Vcc of the grove interface is normally 5v
    grove_vcc = 5

    while True:
        try:
            # Get sensor value
            sensor_value = grovepi.analogRead(sensor)

            # Calculate amplitude current (mA)
            amplitude_current = (float)(sensor_value / 1024 * grove_vcc / 800 * 2000000)

            # Calculate effective value (mA)
            effective_value = amplitude_current / 1.414

            # minimum_current = 1 / 1024 * grove_vcc / 800 * 2000000 / 1.414 = 8.6(mA)
            # Only for sinusoidal alternating current

            print "sensor_value", sensor_value
            print "The amplitude of the current is", amplitude_current, "mA"
            print "The effective value of the current is", effective_value, "mA"
            time.sleep(1)

        except IOError:
            print "Error"

5.Run the demo.

    sudo python grove_electricity_sensor.py

Resources

• Grove -Electricity Sensor Eagle File
• Schematic in PDF

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