Group Assignment

The assignment task: measure the power consumption of an output device

Measure the power consumption of output device by Ammeter

In this week, we are going to test different types of output devices. Our task is measure the power consumption of an output device.

INFO

The power consumption can be caluculated by the following formula:

Power = Voltage(V) * Current (I)

Measure the consumption by Ammeter

We assume the voltage as the power source, which provide 5V voltage. We have to measure the current of the loading component.

We will use a ammeter to measure the current which flow through the loading component.

Choose Ammeter Mode and plug 10A plot to measure the current in (A) resolution.

Ammeter is set a part of circuit and connected with load in series to measure the current.

In this case, we choose connecting the stepper motor and measure the current.

Refer to CHON KIT KUOK's assignment, we connect a stepper motor to controller and connect the controller to ESP32C3.

Then, we setup a ammeter to the power of the controller board. The power source will be set as 5V.

We setup a program that case the stepper motor will spin 1 time with 10rpm speed in clockwise, and spin 1 time with 20rpm speed in counterclockwise.

Program

//Includes the Arduino Stepper Library
#include <Stepper.h>

// Defines the number of steps per rotation
const int stepsPerRevolution = 2038;

// Creates an instance of stepper class
// Pins entered in sequence IN1-IN3-IN2-IN4 for proper step sequence
Stepper myStepper = Stepper(stepsPerRevolution, D0, D2, D1, D3);

void setup() {
    // Nothing to do (Stepper Library sets pins as outputs)
    Serial.begin(115200);
}

void loop() {
	// Rotate CW slowly at 10 RPM
	myStepper.setSpeed(10);
  Serial.println("CW");
	myStepper.step(stepsPerRevolution);
	delay(1000);
	
	// Rotate CCW quickly at 20 RPM
  myStepper.setSpeed(20);
  Serial.println("CCW");
	myStepper.step(-stepsPerRevolution);
	delay(1000);
}

Then, I connect the ammeter as series between power source and Vcc of the controller.

We will measure the current between the power supply (+) and vcc of the controller board.

Case of Stepper Motor (Clockwise in 10 rpm)

We measure the current of loading in stepper motor is about 0.293A during spinning. The current of stepper motor is about 0.32A.

Case of Stepper Motor (CounterClockwise in 20 rpm)

We measure the current of loading in stepper motor is about 0.293A during spinning. The current of stepper motor is about 0.32A when the stepper motor stopped.

Irrelevant to rotation speed, the measured current during spinning is about 0.293A either 10 rpm or 20 rpm. And we measured the current when the stepper motor stopped.

The loading current can be find out by display of power source.

Power Consumption calculation

Assuming the voltage of power source is 5V, we calculate the power consumption is 2 cases: When the stepper motor is:

• Spinning
• Stop

Case of Spinning

The power consumption can be caluculated by the following formula:

Power = Voltage(V) * Current (I)

The power consumption is 5V * 0.293A = 1.465W

Case of Stop

The power consumption can be caluculated by the following formula:

Power = Voltage(V) * Current (I)

The power consumption is 5V * 0.32A = 1.6W

We find out the power consumption of case 'stop' is larger than the case 'spinning'.

Measure the power consumption of output device by Voltage-Current-Capacity Meter

We buy a PowerZ KT002 Voltage-Current-Capacity Meter

Shopping Link of PowerZ KT002 Voltage-Current-Capacity Meter.

It contains a screen which displays:

• Voltage
• Current
• Electricity Consumption in mWh
• Capacity in mAh
• System time

How to measure the power consumption:

• Connect the USB voltage-current-capacity meter to the computer
• Connect the tester output to the XIAO ESP32C3 development board
• Connect a load component, we test the power consumption with a lcd screen as loading.

There's a button which can be used for change the display mode.

Mode 1

It displays:

• Voltage
• Current
• Electricity Consumption in mWh
• Capacity in mAh
• System time

When measuring device power consumption:

• Ah tells you how much charge has been consumed.
• Wh tells you how much energy has been consumed.

Ampere-hours (Ah) is a unit of measurement used to describe the energy capacity of a battery. One ampere-hour is the amount of electric charge transferred by a steady current of one ampere for one hour.

Watt-hours (Wh) is a unit of measurement used to describe the total amount of energy that a battery can store or that an electrical device can use over time. One watt-hour represents the energy used when a power of one watt is sustained for one hour.

The calculation formula is: Wh = V × Ah.

Mode 2

It displays:

• D+ Voltage level
• D- Voltage level
• Voltage
• Current
• Power Consumption in Watt

Mode 3

It displays:

• Voltage
• Current
• Power Consumption in Watt
• Tempature of loading

Here's the power consumption of the lcd monitor:

Parameter	Measured Value
Voltage	5.07893V
Current	0.05403A
Power (Wh)	2.4144Wh
Power (Ah)	0.4903Ah
Power	0.27451 Watt

According the display, we find out that the power consumption is about 2.4144Wh - it represents the energy used when a power of 2.4144 watt is sustained for one hour.