Surajkumar Sharma

Simple Wireless Power Transmission Circuit to Glow an LED

2023-01-08T22:18:00.007+05:30

Simple Wireless Power Transmission Circuit to Glow an LED

In this project, we will build a basic low powered wireless transmitter circuit to glow an LED.

Components Required

Transistor BD 139
LED
Hook up wires
1.2k resistors
Copper wires
1.5V battery

Circuit Diagram

The schematics, for transferring electricity wirelessly to glow an LED, is simple and can be seen in the below image, It has two parts, Transmitter, and the receiver.

At Transmitter side, the coils are connected across the collector of the transistor, 17 turn on both sides. And the receiver is constructed using three components- transistor, resistor, and a center tapped air core inductor or a copper coil. Receiver side has an LED connected across the 34 turns copper coil.

Construction of the Wireless Power Transmission Circuit

Here the transistor used is NPN Transistor, any basic NPN transistor can be used here like BD139.

Coil is the crucial part in wireless energy transfer and should be built carefully. In this project, the coils are made using copper wire of 29AWG. Center tapped coil formation is done on the transmitter side. is used and a cylindrical coil wrapper like PVC pipe is required to wind the coil.

For the transmitter, wind the wire till 17-turns, then the loop for center tap connection and again make 17 turns of coil. And for the receiver, make a 34 turns of coil winding without the center tap.

Working of the Wireless Electricity Transfer Circuit

This circuits is powered using a 1.5V battery. The circuit can’t be used for more than 1.5 volt power supply as transistor may heat up for excessive power dissipation. However, for more rating, additional driving circuits are needed.

This wireless electricity transmission is based on the Inductive coupling technique. The circuit consists of two parts- Transmitter and Receiver.

In transmitter section, the Transistor is generating high-frequency AC current across the coil and the coil is generating a magnetic field around it. As the coil is center tapped, the two sides of the coil start to charge up. One side of the coil is connected to the resistor and another side is connected to the collector terminal of NPN transistor. During the charging condition, the base resistor starts to conduct which eventually turns on the transistor. The transistor then discharges the inductor as the emitter is connected with the ground. This charging and discharging of the inductor produces a very high frequency oscillation signal which is further transmitted as a magnetic field.

On the receiver side, that magnetic field is transferred into the other coil, and by the Faraday’s law of induction, the receiver coil start producing EMF voltage which is further used to light up the LED.

Applications of Wireless Power Transmission

Wireless power transfer (WPT) is a widely discussed topic in the electronics industry. This technology is growing rapidly in the consumer electronics market for smartphones and chargers.

Wireless Energy Transfer can have huge applications and many big companies like Bosch, IKEA, Qi are working on some futuristic solutions using Wireless power transmission.

Pulse Oximeter Sensor with Arduino

2021-05-23T19:02:00.019+05:30

Pulse Oximeter Sensor with Arduino

Interfacing MAX30100 Pulse Oximeter Sensor with Arduino & LCD Display

A pulse oximeter is a device used to monitor both your heart rate and blood oxygen concentration. This device is especially important for people who need to monitor these parameters due to certain health conditions, such as asthma or congestive heart failure.

In this project, 16X2 LCD Display is used to see the value of BPM & SpO2 instead of Serial Monitor. Assemble the circuit as shown in the circuit diagram below.

Connect the Vin pin of MAX30100 to Arduino 5V or 3.3V pin, GND to GND. Connect the I2C Pin, SCL & SDA of MAX30100 to A5 & A4 of Arduino. Similarly connect the LCD pin 1, 5, 16 to GND of Arduino and 2, 15 to 5V VCC. Similarly connect LCD pin 4, 6, 11, 12, 13, 14 to Arduino pin 13, 12, 11, 10, 9, 8. Use 2-10K Potentiometer at pin 3 of LCD to adjust the contrast of LCD.

CONNECTIONS:-

MAX30100-

If you purchased the MAX30100 Module shown below, then it might not work. The MAX30100 IC uses 1.8V for VDD and this particular module uses two regulators to achieve this voltage. Nothing wrong with that.As you can see the SCL and SDA pins are pulled-up via the 4.7k ohm resistors to 1.8V! This means it won’t work well with microcontrollers with higher logic levels.

So to operate it with the higher logic level (3.3V), cut the path in the place of the red cross and make a jumper connection as shown by the yellow line.

CODE:-

#include <LiquidCrystal.h>
#include <Wire.h>
#include "MAX30100_PulseOximeter.h"
 
LiquidCrystal lcd(13, 12, 11, 10, 9, 8);
 
#define REPORTING_PERIOD_MS     1000
 
PulseOximeter pox;
uint32_t tsLastReport = 0;
 
void onBeatDetected()
{
    Serial.println("Beat!");
}
 
void setup()
{
    Serial.begin(115200);
    Serial.print("Initializing pulse oximeter..");
    lcd.begin(16,2);
    lcd.print("Initializing...");
    delay(3000);
    lcd.clear();

 power supply
    if (!pox.begin()) {
        Serial.println("FAILED");
        for(;;);
    } else {
        Serial.println("SUCCESS");
    }
     pox.setIRLedCurrent(MAX30100_LED_CURR_7_6MA);
 
    pox.setOnBeatDetectedCallback(onBeatDetected);
}
 
void loop()
{
    pox.update();
    if (millis() - tsLastReport > REPORTING_PERIOD_MS) {
        Serial.print("Heart rate:");
        Serial.print(pox.getHeartRate());
        Serial.print("bpm / SpO2:");
        Serial.print(pox.getSpO2());
        Serial.println("%");
 
        lcd.clear();
        lcd.setCursor(0,0);
        lcd.print("BPM : ");
        lcd.print(pox.getHeartRate());
        
        lcd.setCursor(0,1);
        lcd.print("SpO2: ");
        lcd.print(pox.getSpO2());
        lcd.print("%");
 
        tsLastReport = millis();
    }
}

OUTPUT:-

Interfacing Stepper Motor with 8051Microcontroller

2021-03-26T12:56:00.009+05:30

Interfacing Stepper Motor with 8051Microcontroller

A stepper motor, also known as a step motor or stepping motor, is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can then be commanded to move and hold at one of these steps without any position sensor for feedback (an open-loop controller), as long as the motor is carefully sized to the application in respect to torque and speed.

Interfacing Stepper Motor with 8051 Microcontroller

We are using Port P0 of 8051 for connecting the stepper motor. HereULN2003 is used. This is basically a high voltage, high current Darlington transistor array. Each ULN2003 has seven NPN Darlington pairs. It can provide high voltage output with common-cathode clamp diodes for switching inductive loads.

Wave Drive Mode − In this mode, one coil is energized at a time. So all four coils are energized one after another. This mode produces less torque than the full-step drive mode.

The following table is showing the sequence of input states in different windings.

Full Drive Mode − In this mode, two coils are energized at the same time. This mode produces more torque. Here the power consumption is also high.
The following table is showing the sequence of input states in different windings.

The circuit diagram is like below:

Source code:

For the wave drive mode-

#include<reg51.h>
#define stepper_motor P0
 
void msdelay(unsigned int time)  // Function for creating delay in milliseconds.
{
    unsigned i,j ;
    for(i=0;i<time;i++)    
    for(j=0;j<1275;j++);
}
 
void main()
{
	while (1) {
		stepper_motor = 0x08;
		msdelay(20);
		stepper_motor = 0x04;
		msdelay(20);
		stepper_motor = 0x02;
		msdelay(20);
		stepper_motor = 0x01;
		msdelay(20);
	}
}

Source code:

For the Full drive mode-

#include<reg51.h>
#define stepper_motor P0
 
void msdelay(unsigned int time)  // Function for creating delay in milliseconds.
{
    unsigned i,j ;
    for(i=0;i<time;i++)    
    for(j=0;j<1275;j++);
}
 
void main()
{
	while (1) {
		stepper_motor = 0x0C;
		msdelay(20);
		stepper_motor = 0x06;
		msdelay(20);
		stepper_motor = 0x03;
		msdelay(20);
		stepper_motor = 0x09;
		msdelay(20);
	}
}

Serial Interrupt Programming in 8051 Microcontroller

2021-03-19T09:45:00.012+05:30

Serial Interrupt Programming in 8051 Microcontroller

Baud Rate calculation:

To meet the standard baud rates generally crystal with 11.0592 MHz is used.
As we know, 8051 divides crystal frequency by 12 to get a machine cycle frequency of 921.6 kHz.
The internal UART block of 8051 divides this machine cycle frequency by 32, which gives the frequency of 28800 Hz which is used by UART.
To achieve a baud rate of 9600, again 28800 Hz frequency should be divided by 3.
This is achieved by using Timer1 in mode-2 (auto-reload mode) by putting 253 in TH1 (8-bit reg.)
So 28800 Hz will get divided by 3 as the timer will overflow after every 3 cycles.
we can achieve different baud rates by putting the division factor in the TH1 register.

Division factor to achieve different baud rates

Baud Rate	TH1 (Hex)
9600	FD
4800	FA
2400	F4
1200	E8

SCON: Serial Control Register

Serial control register SCON is used to set serial communication operation modes. Also, it is used to control transmit and receive operations.

Bit 7:6 - SM0:SM1: Serial Mode Specifier

Mode	SM0	SM1	Mode
0	0	0	1/12 of Osc frequency shift register mode fixed baud rate
1	0	1	8-bit UART with timer 1 determined baud rate
2	1	0	9-bit UART with 1/32 of Osc fixed baud rate
3	1	1	9-bit UART with timer 1 determined baud rate

Normally mode-1 (SM0 =0, SM1=1) is used with 8 data bits, 1 start bit, and 1 stop bit.

Bit 5 - SM2: for Multiprocessor Communication

This bit enables a multiprocessor communication feature in mode 2 & 3.

Bit 4 - REN: Receive Enable

1 = Receive enable

0 = Receive disable

Bit 3 - TB8: 9th Transmit Bit

This is the 9th bit which is to be transmitted in mode 2 & 3 (9-bit mode)

Bit 2 - RB8: 9th Receive Bit

This is the 9th received bit in mode 2 & 3 (9-bit mode), whereas in mode 1 if SM2 = 0 then RB8 hold the stop bit that received

Bit 1 - TI: Transmit Interrupt Flag

This bit indicates the transmission is complete and gets set after transmitting the byte from the buffer. Normally TI (Transmit Interrupt Flag) is set by hardware at the end of the 8th bit in mode 0 and at the beginning of the stop bit in other modes.

Bit 0 – RI: Receive Interrupt Flag

This bit indicates reception is complete and gets set after receiving the complete byte in the buffer. Normally RI (Receiver Interrupt Flag) is set by hardware in receiving mode at the end of the 8th bit in mode 0 and at the stop bit receive time in other modes.

Programming steps:

Configure Timer 1 in auto-reload mode.
Load TH1 with value as per required baud rate e.g. for 9600 baud rate load 0xFD. (-3 in decimal)
Load SCON with serial mode and control bits. e.g. for mode 1 and enable reception, load 0x50.
Start timer1 by setting TR1 bit to 1.
Load transmitting data in the SBUF register.
Wait until loaded data is completely transmitted by polling the TI flag.
When the TI flag is set, clear it, and repeat from step 5 to transmit more data.

Write an 8051 C program to transfer "YES" serially at 9600 baud rate, 8-bit data,1 stop bit, Do it continuously.

CODE:-

/*Write an 8051 C program to transfer "YES" serially at 9600 baud rate,
 8-bit data,1 stop bit, Do it for 5 times.
*/
#include <reg51.h>
void SerTx(unsigned char);
unsigned int i = 0;

void SerTx(unsigned char ch)
 {
    SBUF = ch;              //loading value in buffer
    while(TI==0);         //wait untill transmition is over
    TI=0; 
 }

void main(void)
{
TMOD = 0x20;           //use Timer 1, 8-bit auto-reload
TH1 = 0xFD;              //9600 baud rate
SCON = 0x50;
TR1 = 1;	               //start timer
for(i;i<5;i++)
	{
	   SerTx('Y');
	   SerTx('E');
	   SerTx('S');
	}
	while(1);
}

Write an 8051 C program to receive bytes of data serially and put them in P2.

Set baud rate at 9600, 8-bit data, and 1 stop bit.

CODE:-

// Program in 8051  in C to receive bytes of data serially and put them in P2.
// Set baud rate at 4800, 8-bit data, and 1 stop bit.

#include <reg51.h>

void main (void)
 {
   unsigned char myData;
   TMOD = 0x20;         //use Timer-1,8-bit auto-reload
   TH1 = 0xFD;            //9600 baud rate
   SCON = 0x50;
   TR1 = 1;                   //start timer
   while(1)
        {
	       while(RI==0);
	       myData = SBUF;
	       P2=myData;
	       RI=0;
	  }
 }

Alternet way using Serial interrupt:-


#include <reg51.h>	/* Include x51 header file */

void Ext_int_Init()				
{
  EA = 1;	/* Enable global interrupt */
  ES = 1;  	/* Enable serial interrupt */			
}

void UART_Init()
{
  TMOD = 0x20;	/* Timer 1, 8-bit auto reload mode */
  TH1 = 0xFD;	      /* Load value for 9600 baud rate */
  SCON = 0x50;	      /* Mode 1, reception enable */
  TR1 = 1;	            /* Start timer 1 */
}

void Serial_ISR() interrupt 4    
{
  P2 = SBUF;	   /* Give received data on port 1 */
  RI = 0;	         /* Clear RI flag */
} 

void main()
{
  P2 = 0x00;	   /* Make P2 output */
  Ext_int_Init();  /* Call Ext. interrupt initialize */
  UART_Init();
  while(1);
}

LCD Interfacing with 8051 Microcontroller

2021-03-09T11:16:00.018+05:30

LCD Interfacing with 8051 Microcontroller

Hex Code	Command to LCD Instruction Register
0F	LCD ON, cursor ON
01	Clear display screen
02	Return home
04	Decrement cursor (shift cursor to left)
06	Increment cursor (shift cursor to right)
05	Shift display right
07	Shift display left
0E	Display ON, cursor blinking
80	Force cursor to the beginning of the first line
C0	Force cursor to the beginning of the second line
38	2 lines and 5×7 matrix
83	Cursor line 1 position 3
3C	Activate the second line
08	Display OFF, cursor OFF
C1	Jump to the second line, position 1
OC	Display ON, cursor OFF
C1	Jump to the second line, position 1
C2	Jump to a second line, position 2

Circuit Diagram :

Source Code:

// Program for LCD Interfacing with 8051 Microcontroller (P89V51RD2) 

#include<reg51.h>
#include <string.h>

#define display_port P2      //Data pins connected to port 2 on microcontroller
sbit rs = P0^0;  //Register Select pin connected to pin 0 of port 0
sbit rw = P0^1;  // Read/Write pin connected to pin 0 of port 1
sbit e =  P0^2;  //Enable pin connected to pin 0 of port 2

void msdelay(unsigned int time)  // Function for creating delay in milliseconds.
{
    unsigned i,j ;
    for(i=0;i<time;i++)    
    for(j=0;j<1275;j++);
}
void lcd_cmd(unsigned char command)  //Function to send command instruction to LCD
{
    display_port = command;
    rs= 0;
    rw=0;
    e=1;
    msdelay(1);
    e=0;
}

void lcd_data(unsigned char disp_data)  //Function to send display _data to LCD
{
    display_port = disp_data;
    rs= 1;
    rw=0;
    e=1;
    msdelay(1);
    e=0;
}

 void lcd_init()    //Function to prepare the LCD  and get it ready
{
    lcd_cmd(0x38);  // for _using 2 lines and 5X7 matrix of LCD
    msdelay(10);
    lcd_cmd(0x0F);  // turn display ON, cursor blinking
    msdelay(10);
    lcd_cmd(0x01);  //clear screen
    msdelay(10);
    lcd_cmd(0x81);  // bring cursor to position 1 of line 1
    msdelay(10);
}
void main()
{
    unsigned char a[15]="Surajkumar";    //string of 14 characters with a null terminator.
    int l=0;
		int len = strlen(a);
	
    lcd_init();
	
		for(l;l<len;l++)
		{
			lcd_data(a[l]);
			msdelay(50);
			
		} 
		
	   // OR
	
		
    //while(a[l] != '\0') // searching the null terminator in the sentence
    //{
    //    lcd_data(a[l]);
    //    l++;
    //    msdelay(50);
    //}
 
  while(1);

}

Control LEDs with Voice Command

2021-03-08T15:28:00.009+05:30

Control LEDs with Voice Command

This is a very basic project for controlling LED (Red) using voice control. To accomplish this we have used the Bluetooth HC-05 module and android apps are available on the play store. LEDs will be On/Off on your voice command.

Procedure:-

Make the connections as shown in the connection image. Don’t connect the RX & TX pins WHILE/BEFORE uploading the code!
Copy the code given below.
Download any app called BT Voice Control.
Open the app (It will automatically turn on the device’s Bluetooth). Go to options. Click on “Connect”. Choose the device – HC 05.
When you are connecting to the Bluetooth module for the first time, it will ask you for the password. Enter 0000 OR 1234.
When the device gets successfully paired with the sensor, the LED lights on the sensor will start blinking at a slower rate than usual.
DONE. Copy the code given below & test it out!

Source Code:-

String voice;
#define RED 8

void setup() {
  Serial.begin(9600);
  pinMode(RED,OUTPUT);
}
 

void RedOn(){
digitalWrite (RED, HIGH);
}
void RedOff(){
digitalWrite (RED, LOW);
}

 
void loop() {                    
  while (Serial.available()){  //Check if there is an available byte to read
  delay(10);                   //Delay added to make thing stable
  char c = Serial.read();      //Conduct a serial read
  if (c == '#') {break;}       //Exit the loop when the # is detected after the word
  voice += c; //Shorthand for voice = voice + c
  } 
  if (voice.length() > 0) {
    Serial.println(voice);
//-----------------------------------------------------------------------//   
  //----------Control Multiple Pins/ LEDs----------// 
   if(voice =="red" || voice =="red on"){
        RedOn();
    }
    else if(voice =="red off"){
        RedOff();
    }

voice=""; //Reset the variable after initiating
}
}

Connections:-

Bluetooth:- Arduino UNO:-

RxD ==> TxD

TxD ==> RxD

Vcc ==> 3.3V

Gnd ==> Gnd

LM386 based audio amplifier

2021-03-07T13:55:00.017+05:30

LM386 based audio amplifier: circuit and working.

we will show you how to build LM386 Audio Amplifier Circuit. It is a very low-cost audio amplifier and can power any speaker. For the cost and size of the circuit, the sound from the LM386 Audio Amplifier can be adequately loud.
There are many Audio Amplifier Circuits designed using LM386 IC. The main problem with these circuits is noise and interference. The noise from the Amplifier Circuit designed in this project is considerably less and if designed on a proper circuit board, this will make a great Audio Amplifier.

Introduction to LM386

The LM386 is an all–in–one Class-AB Audio Amplifier IC that can be used in a variety of applications. LM386 IC has been in use for decades and is still being used as an Amplifier in Computer speakers and Portable Stereos.

LM386 is a low voltage power amplifier with an inactive power draw of 24mW, which makes it suitable for battery-controlled applications. The most common package for LM386 is an 8 – pin DIP.

Schematic of LM386 Audio Amplifier Circuit

Before using this project, test it using the 6V battery. Connect the 8-ohm, one-watt speaker to output pin 5 of IC1 through C3. Switch on S1 and keep VR1 to its mid position. Now, take a screwdriver and gently touch it on input terminal pin 3 of IC1. You should hear a humming sound from the speaker. This will confirm that your circuit is working and ready to use.

Features of IC LM386

The main features of LM386 chip include the following.

IC LM386 is obtainable in the package of 8-pin MSOP
Exterior components are minimum
Operation of Battery
Low static power drain- 4mA
The range of supply voltage is wide which is ranges from 4Volts to 12Volts or 5Volts to 18 Volts.
Input is referenced by ground
Distortion is less 0.2%
Self-centering o/p static voltage
The voltage gain range will be from 20 to 200

Interfacing LED with 8051 Microcontroller in Assembly

2021-02-18T21:59:00.024+05:30

Blinking 1 LED using 8051

This is the first project regarding 8051 and of course one of the simplest, blinking LEDs using 8051. The microcontroller used here is AT89S51 In the circuit, push-button switch S1, capacitor C3 and resistor R3 form the reset circuitry. When S1 is pressed, the voltage at the reset pin (pin9) goes high and this resets the chip. C1, C2, and X1 are related to the on-chip oscillator which produces the required clock frequency. P1.0 (pin1) is selected as the output pin. When P1.o goes high the transistor Q1 is forward biased and LED goes ON. When P1.0 goes low the transistor goes to cut off and the LED extinguishes. The transistor driver circuit for the LED can be avoided and the LED can be connected directly to the P1.0 pin with a series current limiting resistor(~1K). The time for which P1.o goes high and low (the time period of the LED) is determined by the program. The circuit diagram for blinking 1 LED is shown below.

Program.

START: CPL P1.0
       ACALL WAIT  
       SJMP START

WAIT:  MOV R4,#05H
WAIT1: MOV R3,#00H
WAIT2: MOV R2,#00H
WAIT3: DJNZ R2,WAIT3
        DJNZ R3,WAIT2
        DJNZ R4,WAIT1
        RET

Blinking  2 LED alternatively using 8051.
This circuit can blink two LEDs alternatively. P1.0 and P1.1 are assigned as the outputs. When P1.0 goes high P1.0 goes low and vice versa and the LEDs follow the state of  the corresponding port to which it is connected. Here there is no driver stage for the LEDs and they are connected directly to the corresponding ports through  series current limiting resistors (R1 & R2). Circuit diagram is shown below. 

Program.

START: CPL P1.0
       ACALL WAIT  
       CPL P1.0
       CPL P1.1
       ACALL WAIT
       CPL P1.1  
       SJMP START

WAIT:  MOV R4,#05H
WAIT1: MOV R3,#00H
WAIT2: MOV R2,#00H
WAIT3: DJNZ R2,WAIT3
        DJNZ R3,WAIT2
        DJNZ R4,WAIT1
        RET