Showing posts with label Info. Show all posts
Showing posts with label Info. Show all posts

RFID CARD READER WITH ARDUINO, RFID-RC522 and LCD 16x2



Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. The tags contain electronically stored information. Passive tags collect energy from a nearby RFID reader's interrogating radio waves. Active tags have a local power source such as a battery and may operate at hundreds of meters from the RFID reader. Unlike a barcode, the tag need not be within the line of sight of the reader, so it may be embedded in the tracked object. RFID is one method for Automatic Identification and Data Capture (AIDC).
RFID tags are used in many industries, for example, an RFID tag attached to an automobile during production can be used to track its progress through the assembly line; RFID-tagged pharmaceuticals can be tracked through warehouses; and implanting RFID microchips in livestock and pets allows positive identification of animals.
Since RFID tags can be attached to cash, clothing, and possessions, or implanted in animals and people, the possibility of reading personally-linked information without consent has raised serious privacy concerns. These concerns resulted in standard specifications development addressing privacy and security issues. ISO/IEC 18000 and ISO/IEC 29167 use on-chip cryptography methods for un-traceability, tag and reader authentication, and over-the-air privacy. ISO/IEC 20248 specifies a digital signature data structure for RFID and barcodes providing data, source and read method authenticity. This work is done within ISO/IEC JTC 1/SC 31 Automatic identification and data capture techniques.
COMPONENTS:
  • RFID RC-522
  • ARDUINO UNO
  • LED
  • BUZZER
  • JUMPPER WIRES
  • BATTERY (9V WITH CAP)
  • PLUG (5 x 2.1)
  • LCD (16 x 2)
  • ADDITIONAL CONNECTION PINS
  • RISISTANCE (220 ohm) (x 2)
  • VARIABLE RESISTOR (10 K)
CIRCUIT DIAGRAM:


ARDUINO CODE:
  • /*------------------------------------------
  •   RFID CARD READER 
  •   By https://nonstopengineering.blogspot.com/
  •   Using Arduino,RFID-RC522 and LCD 16x2
  •   ------------------------------------------*/

  • #include <EEPROM.h>  //Library To read and write PICC's UIDs from/to EEPROM
  • #include <SPI.h>      //Library  RC522 Module uses SPI protocol
  • #include <MFRC522.h> //Library  RC522 Module
  • #include <LiquidCrystal.h> //Library  for LCD Display

  • boolean match = false; // initialize card match to false
  • boolean programMode = false; // initialize programming mode to false
  • int successRead; // Variable integer to keep if we have Successful Read from Reader
  • byte storedCard[4];   // Stores an ID read from EEPROM
  • byte readCard[4];           // Stores scanned ID read from RFID Module
  • byte masterCard[4]; // Stores master card's ID read from EEPROM
  • #define SS_PIN 10
  • #define RST_PIN 9
  • MFRC522 mfrc522(SS_PIN, RST_PIN);  // Create MFRC522 instance.
  • LiquidCrystal lcd(7, 6, 5, 4, 3, 2); //Initializing LCD PINS as (RS,EN,D4,D5,D6,D7)
  • void setup() {
  •   // put your setup code here, to run once:
  •   Serial.begin(9600);  // Initialize serial communications with PC
  •   lcd.begin(16, 2);    //Initializing LCD 16x2
  •   pinMode(8, OUTPUT);  //LED and Buzzer PIN OUT
  •   SPI.begin();           // MFRC522 Hardware uses SPI protocol
  •   mfrc522.PCD_Init();    // Initialize MFRC522 Hardware
  •   mfrc522.PCD_SetAntennaGain(mfrc522.RxGain_max);
  •   if (EEPROM.read(1) != 1) {  // Look EEPROM if Master Card defined, EEPROM address 1 holds if defined
  •     Serial.println("No Master Card Defined"); //When no Master Card in Your EEROM (Serial Display)
  •     Serial.println("Scan A PICC to Define as Master Card");
  •     lcd.clear();
  •     lcd.setCursor(0, 0);
  •     lcd.println("SET MASTERCARD   "); //When no Master Card in Your EEROM (LCD Display)
  •     lcd.setCursor(0, 1);
  •     lcd.println("SCAN A PICC....."); //Scan any RFID CARD to set Your Master Card in Your EEROM (LCD Display)
  •     delay(1500);
  •     do {
  •       successRead = getID(); // sets successRead to 1 when we get read from reader otherwise 0
  •     }
  •     while (!successRead); //the program will not go further while you not get a successful read
  •     for ( int j = 0; j < 4; j++ ) { // Loop 4 times
  •       EEPROM.write( 2 + j, readCard[j] ); // Write scanned PICC's UID to EEPROM, start from address 3
  •     }
  •     EEPROM.write(1, 1); //Write to EEPROM we defined Master Card.
  •     Serial.println("Master Card Defined");
  •     
  •   }
  •   Serial.println("Master Card's UID");
  •   for ( int i = 0; i < 4; i++ ) {     // Read Master Card's UID from EEPROM
  •     masterCard[i] = EEPROM.read(2 + i); // Write it to masterCard
  •     Serial.print(masterCard[i], HEX); //Master Card only view in serial
  •      Serial.println("Waiting PICCs to bo scanned :)"); 
  •   }
  •   //WAITING TO SCAN THE RFID CARDS:
  •   Serial.println("");
  •   Serial.println("Waiting PICCs to bo scanned :)");
  •   lcd.clear();
  •   lcd.setCursor(0, 0);
  •   lcd.println("WAITING         ");
  •   lcd.setCursor(0, 1);
  •   lcd.println("FOR PICC....     ");
  •   delay(1500);
  • }
  • void loop() {
  •   lcd.clear();
  •   lcd.setCursor(0, 0);
  •   lcd.print("      SWIPE");
  •   lcd.setCursor(0, 1);
  •   lcd.print("    YOUR CARD");

  •  /* 
  •  if (digitalRead(BUTTON) == HIGH);                     //To Delete the EEROM USE the below command just run it
  •   {
  •   // for (int i = 0 ; i < EEPROM.length() ; i++) {
  •   // EEPROM.write(i, 0);
  •   // }
  •   // }                                     */
  •   do {
  •     successRead = getID(); // sets successRead to 1 when we get read from reader otherwise 0
  •     if (programMode) {
  •       // Program Mode cycles through RGB waiting to read a new card
  •     }
  •     else {
  •    }}
  •   while (!successRead); //the program will not go further while you not get a successful read
  •   if (programMode) {
  •     if ( isMaster(readCard) ) {  //If master card scanned again exit program mode
  •       Serial.println("This is Master Card");
  •       Serial.println("Exiting Program Mode");
  •       lcd.clear();
  •       lcd.setCursor(0, 0);
  •       lcd.print("EXITING FROM");
  •       lcd.setCursor(0, 1);
  •       lcd.print("MASTERCARD MODE");
  •       delay(2000);
  •       programMode = false;
  •       return;
  •     }
  •     else {
  •       if ( findID(readCard) ) { //If scanned card is known delete it
  •         Serial.println("I know this PICC, so removing");
  •         lcd.clear();
  •         lcd.setCursor(0, 0);
  •         lcd.print("AVAILABLE!");
  •         lcd.setCursor(0, 1);
  •         lcd.print("SO DELETING.....");
  •         delay(5000);
  •         deleteID(readCard);
  •         Serial.println("-----------------------------");
  •       }
  •       else {                    // If scanned card is not known add it
  •         Serial.println("I do not know this PICC, adding...");
  •         lcd.clear();
  •         lcd.setCursor(0, 0);
  •         lcd.print("Card no:");
  •         lcd.setCursor(0, 1);
  •         lcd.print(readCard[0], HEX);
  •         lcd.print(readCard[1], HEX);
  •         lcd.print(readCard[2], HEX);
  •         lcd.print(readCard[3], HEX);
  •         lcd.print(readCard[4], HEX);
  •         delay(4000);
  •         lcd.clear();
  •         lcd.setCursor(0, 0);
  •         lcd.print("NOT AVAILABLE");
  •         lcd.setCursor(0, 1);
  •         lcd.print("SO ADDING.......");
  •         delay(5000);
  •         writeID(readCard);
  •         Serial.println("-----------------------------");
  •       }} }
  •   else {
  •     if ( isMaster(readCard) ) {  // If scanned card's ID matches Master Card's ID enter program mode
  •       programMode = true;
  •       Serial.println("Welcome to Mastercard Mode");
  •       lcd.clear();
  •       lcd.setCursor(0, 0);
  •       lcd.print("WELCOME TO");
  •       lcd.setCursor(0, 1);
  •       lcd.print("MASTERCARD MODE");
  •       delay(3000);
  •       int count = EEPROM.read(0); // Read the first Byte of EEPROM that
  •       Serial.print("I have ");    // stores the number of ID's in EEPROM
  •       Serial.print(count);
  •       Serial.print(" record(s) on EEPROM");
  •       Serial.println("");
  •       Serial.println("Scan a PICC to ADD or REMOVE");
  •       Serial.println("-----------------------------");
  •       lcd.clear();
  •       lcd.setCursor(0, 0);
  •       lcd.print("SCAN PICC TO");
  •       lcd.setCursor(0, 1);
  •       lcd.print("ADD OR REMOVE...");
  •       delay(2500);
  •     }
  •     else {
  •       if ( findID(readCard) ) {        // If not, see if the card is in the EEPROM
  •         Serial.println("Acces Granted");
  •         lcd.clear();
  •         lcd.setCursor(0, 0);
  •         lcd.print(" CONGRATULATION");
  •         lcd.setCursor(0, 1);
  •         lcd.print(" ACCESS GRANTED");
  •         digitalWrite(8, HIGH);
  •         delay(1500);
  •         digitalWrite(8, LOW);
  •         lcd.clear();
  •       }
  •       else {        // If not, show that the ID was not valid
  •         Serial.println("Access Denied");
  •         for (int abcd = 0; abcd < 6; abcd++)
  •         {
  •           lcd.clear();
  •           lcd.setCursor(0, 0);
  •           lcd.print("     SORRY");
  •           lcd.setCursor(0, 1);
  •           lcd.print("  ACCESS DENIED");
  •           digitalWrite(8, HIGH);
  •           delay(700);
  •           digitalWrite(8, LOW);
  •           lcd.clear();
  •           lcd.print("   YOU'RE NOT  ");
  •           lcd.setCursor(0, 1);
  •           lcd.print("   AUTHORIZED   ");
  •           delay(700);
  •         }
  •         lcd.clear();
  •       }}}}
  • int getID() {
  •   // Getting ready for Reading PICCs
  •   if ( ! mfrc522.PICC_IsNewCardPresent()) { //If a new PICC placed to RFID reader continue
  •     return 0;
  •   }
  •   if ( ! mfrc522.PICC_ReadCardSerial()) { //Since a PICC placed get Serial and continue
  •     return 0;
  •   }
  •   // There are Mifare PICCs which have 4 byte or 7 byte UID care if you use 7 byte PICC
  •   // I think we should assume every PICC as they have 4 byte UID
  •   // Until we support 7 byte PICCs

  •   Serial.println("Scanning PICC's UID.........");
  •   lcd.clear();
  •   lcd.setCursor(0, 0);
  •   lcd.print("SCANNING");
  •   lcd.setCursor(0, 1);
  •   lcd.print("PICC's UID.....");
  •   delay(2000);
  •   for (int i = 0; i < 4; i++) {  //
  •     readCard[i] = mfrc522.uid.uidByte[i];
  •     Serial.print(readCard[i], HEX);
  •   }
  •   Serial.println("");
  •   mfrc522.PICC_HaltA(); // Stop reading
  •   return 1;
  • }
  • boolean isMaster( byte test[] ) {
  •   if ( checkTwo( test, masterCard ) )
  •     return true;
  •   else
  •     return false;
  • }

  • boolean checkTwo ( byte a[], byte b[] ) {
  •   if ( a[0] != NULL ) // Make sure there is something in the array first
  •     match = true; // Assume they match at first
  •   for ( int k = 0; k < 4; k++ ) { // Loop 4 times
  •     if ( a[k] != b[k] ) // IF a != b then set match = false, one fails, all fail
  •       match = false;
  •   }
  •   if ( match ) { // Check to see if if match is still true
  •     return true; // Return true
  •   }
  •   else  {
  •     return false; // Return false
  •   }}
  • boolean findID( byte find[] ) {
  •   int count = EEPROM.read(0); // Read the first Byte of EEPROM that
  •   for ( int i = 1; i <= count; i++ ) {  // Loop once for each EEPROM entry
  •     readID(i); // Read an ID from EEPROM, it is stored in storedCard[4]
  •     if ( checkTwo( find, storedCard ) ) { // Check to see if the storedCard read from EEPROM
  •       return true;
  •       break; // Stop looking we found it
  •     }
  •     else {  // If not, return false
  •     }}
  •   return false;
  • }
  • void readID( int number ) {
  •   int start = (number * 4 ) + 2; // Figure out starting position
  •   for ( int i = 0; i < 4; i++ ) { // Loop 4 times to get the 4 Bytes
  •     storedCard[i] = EEPROM.read(start + i); // Assign values read from EEPROM to array
  •   }
  • }
  • void deleteID( byte a[] ) {
  •   if ( !findID( a ) ) { // Before we delete from the EEPROM, check to see if we have this card!
  •     failedWrite(); // If not
  •   }
  •   else {
  •     int num = EEPROM.read(0); // Get the numer of used spaces, position 0 stores the number of ID cards
  •     int slot; // Figure out the slot number of the card
  •     int start;// = ( num * 4 ) + 6; // Figure out where the next slot starts
  •     int looping; // The number of times the loop repeats
  •     int j;
  •     int count = EEPROM.read(0); // Read the first Byte of EEPROM that stores number of cards
  •     slot = findIDSLOT( a ); //Figure out the slot number of the card to delete
  •     start = (slot * 4) + 2;
  •     looping = ((num - slot) * 4);
  •     num--; // Decrement the counter by one
  •     EEPROM.write( 0, num ); // Write the new count to the counter
  •     for ( j = 0; j < looping; j++ ) { // Loop the card shift times
  •       EEPROM.write( start + j, EEPROM.read(start + 4 + j)); // Shift the array values to 4 places earlier in the EEPROM
  •     }
  •     for ( int k = 0; k < 4; k++ ) { //Shifting loop
  •       EEPROM.write( start + j + k, 0);
  •     }
  •     successDelete();
  •   }}
  •   //For Failed to add the card:
  • void failedWrite() {

  •   Serial.println("something wrong with Card");
  •   lcd.clear();
  •   lcd.setCursor(0, 0);
  •   lcd.print("SOMETHING WRONG");
  •   lcd.setCursor(0, 1);
  •   lcd.print("WITH CARD");
  •   delay(2000);
  • }
  • //For Sucessfully Deleted:
  • void successDelete() {
  •   Serial.println("Succesfully removed");
  •   lcd.clear();
  •   lcd.setCursor(0, 0);
  •   lcd.print("SUCCESFULLY");
  •   lcd.setCursor(0, 1);
  •   lcd.print("REMOVED");
  •   delay(2000);
  • }
  • int findIDSLOT( byte find[] ) {
  •   int count = EEPROM.read(0); // Read the first Byte of EEPROM that
  •   for ( int i = 1; i <= count; i++ ) { // Loop once for each EEPROM entry
  •     readID(i); // Read an ID from EEPROM, it is stored in storedCard[4]
  •     if ( checkTwo( find, storedCard ) ) { // Check to see if the storedCard read from EEPROM
  •       // is the same as the find[] ID card passed
  •       return i; // The slot number of the card
  •       break; // Stop looking we found it
  •     }
  •   }
  • }
  • //For Sucessfully Added:
  • void successWrite() {

  •   Serial.println("Succesfully added");
  •   lcd.clear();
  •   lcd.setCursor(0, 0);
  •   lcd.print("SUCCESFULLY");
  •   lcd.setCursor(0, 1);
  •   lcd.print("ADDED");
  •   delay(2000);
  • }
  • //For Adding card to EEROM:
  • void writeID( byte a[] ) {
  •   if ( !findID( a ) ) { // Before we write to the EEPROM, check to see if we have seen this card before!
  •     int num = EEPROM.read(0); // Get the numer of used spaces, position 0 stores the number of ID cards
  •     int start = ( num * 4 ) + 6; // Figure out where the next slot starts
  •     num++; // Increment the counter by one
  •     EEPROM.write( 0, num ); // Write the new count to the counter
  •     for ( int j = 0; j < 4; j++ ) { // Loop 4 times
  •       EEPROM.write( start + j, a[j] ); // Write the array values to EEPROM in the right position
  •     }
  •     successWrite();
  •   }
  •   else {
  •     failedWrite();
  •   }
  • }


ARDUINO CODE FILE → CLICK HERE

WORKING:






Designing of Dipole Antenna

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The most commonly used antenna is the dipole antenna used for RF with the most common applications being old tv transmissions. Widely used on its own, it is also incorporated into other RF antenna designs as well, as the driven element. The calculations for an antenna might be complex, a simple dipole antenna however is pretty easy to design. The in-depth analysis to increase the gain and other parameters however are a different struggle.


DIPOLE ANTENNA BASICS:

The two poles/terminals of the antenna are used as either transmitters or receivers based on the usage. The parameters of the signal cause the signal to be transmitted from the antenna.

At the transmitting end, the signal is fed to the antenna which is split in the middle, to accommodate the feeder. Similarly, at the receiving end, the split is used to take power from the receiver. The length of the antenna is carefully calculated before designing one for your application. It is proportional to the wavelength of your signal in question depending on the type of antenna and application.
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The length of most commonly used, half wave dipole antenna is half the wavelength of your signal in question. This resonates with the signal where the electrical length is again half a wavelength long.

As the name suggests, the two parts of the antenna are conductive and can be easily designed from metal wires. These are fed by a signal source for the transmitter or a power source at the reception end. The form of transmission of signal from or to the antenna leaves for a lot of designs. Let’s take a look at some of the variations that might suit your applications.

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TYPES OF DIPOLE:

Some of the variations of the dipole antenna could be
  • Half wave dipole antenna: This is the most common type of antenna with length of about half the wavelength of the signal.
  • Multiple half waves dipole antenna: Odd multiple of half wavelengths long dipole antenna can also be used if required.
  • Folded dipole antenna: While still retaining the length between the ends of half a wavelength, an additional length of conductor connects the two ends together i.e. the antenna is folded back on itself.
  • Short dipole: This would be the sortest variant of the dipole antenna. The length if the antenna is much smaller than the half wavelength. However, the feed impedance starts to rise and its response is less dependent upon frequency changes.The reduced length has other advantages.
  • Non-resonant dipole: Non-resonance in an antenna helps in operating of the antenna over a very wide bandwidth. It can also be operated away from its resonant frequency and fed with a high impedance feeder.

DIPOLE ANTENNA AND VOLTAGE DISTRIBUTION:

The values of parameters on a radiating element vary on a dipole. The is due to the standing wave phenomenon, which form along the length of the dipole.

Both the current and voltage on the dipole antenna vary in a sinusoidal manner, meaning that there may be other peaks and troughs along the length of the radiating sections dependent upon their length.

Basic Concepts about Antenna Design

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Antenna design begins by understanding your transmission requirements. You need to know the wavelength / frequency of the signal for the antenna, before beginning work on antenna design. The next step is understanding the antenna type that would suit your application. Moreover certain applications would require several antenna and this may cause a confusion for novices.

A LIST OF CURRENTLY USED ANTENNA:
A detailed list of antennas has been mentioned below for your reference. This list is being further updated on a regular basis.

Monopole Antenna                       Helical Antenna                      Log-Periodic Dipole
Dipole Antenna                                 Yagi-Uda                                 Slot Antenna
Short-Dipole                                 Spiral Antenna                     Cavity-Backed Slot
Half-wave dipole                          Corner Reflector                          Horn Antenna
Broadband Dipole                      Parabolic Reflector                      Vivaldi Antenna
Folded Dipole                                 Microstrip patch                    Slotted Waveguide
Loop Antenna                              Planar Inverted-F                            Inverted-F
Cloverleaf Antenna                               Bow-Tie                         Antenna in wearable

PARAMETERS IN ANTENNA DESIGN:

All of these and more are being used in some or the other application around us. However designing any of them would involve understanding parameters and suitability for a particular application. Some parameters involved with antenna design besides basic aesthetics are the antenna resonance point or the operating frequency, and the antenna bandwidth or the range of frequencies over which this antenna would be expected to operate.

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Any RF antenna consists of capacitive and inductive components in it’s design. Hence this calls for tuning between the two. This brings in a resonance point into the picture. You might be familiar with the relation between capacitance and inductance in tank circuits.

By varying the values of inductance (L) and capacitance (C) in the circuit, we can tune the circuit to receive a particular frequency. This may sound simplistic in reality, However, practical implementation, shows that a circuit tuned at a particular frequency receives a range of frequencies. This brings in another factor the range of operation for the antenna.

Most RF antennas operate upto a certain range of frequencies about the resonant frequency. This becomes a necessity, as the signal transmitted at a particular frequency would undergo several modifications, during its travel. This allows a range of frequencies to pass through, but outside the range the reactance rises to levels that are often too high for satisfactory operation. Other characteristics of the antenna may also suffer due to the increased range of frequencies hence the tank circuit filters the frequencies about the central operating frequency.


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tank circuit

Impedance Bandwidth:

The impedance of an RF antenna stays same and does not change with its frequency. This causes an increase in the amount of reflected power. In case of a transmitting antenna, beyond a given level of reflected power, damage may occur to either the transmitter or the feeder. This would be a significant factor limiting the operating bandwidth of an antenna but not so much on the reception end.

As far as receiving is concerned the impedance changes of the antenna are not as critical as it will mean that the signal transfer from the antenna itself to the feeder is reduced and will cause the efficiency to fall.

In order to increase the bandwidth of an antenna there are a number of measures that can be taken for eg. using thicker conductors.

Design Cell Phone Jammer Project

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Cell phone jammer is an electronic device that blocks transmission of signals between a cell phone and a base station. By using the same frequency as a mobile handset, the cell phone jammer creates strong interference for communication between the caller and receiver. It is efficient in blocking transmission of signals from networks including UMTS, 3G, CDMA, GSM and PHS.

Mobile phones operate at different frequency bands in different countries. For Canada the 1900 MHz band is the primary band, particularly for urban areas. 850 MHz is used as a backup in rural areas. USA uses 850 and 1900 MHz bands, depending on the area. Europeans tend to use the GSM 900 and 1800 bands as standard. Middle East, Africa, Asia and Oceania also use these frequency bands. In Russia and some other countries, local carriers have licenses for 450 MHz frequency to provide CDMA coverage.

The use of different frequencies makes it difficult to have a jammer for all frequencies. However the below mentioned formula can be used to calculate the required values.

F= 1/ (2*pi*sqrt (L1*C1))

Depending on the frequencies you need to block, the values of inductor (L1) and capacitor (C1) can be altered.

For example, if mobile phones at your area work at 450 MHz, you need to generate 450 MHz with some noise to act as the blocking signal. Now the cell phone receiver will not be able to understand, which signal to receive. We have successfully blocked cell phone signals.

Here, 450MHz is the tuning frequency. L1 and C1 values are calculated using the formula above. Cell phone jammers for other frequency ranges are designed similarly. However, the signal range is very weak. Thus, this circuit works only for a range of 100 m.

CIRCUIT:
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NOTE:
  • This circuit can block signals only within a 100 meter radius.
  • Usage of this type of circuits is banned and illegal in most countries.
  • This circuit is also used in TV transmission and remote controlled toys.
  • If the circuit is not working properly, try increasing resistor and capacitors values in the circuit. Use the formula

F= 1/ (2*pi*sqrt (L*C)).

  • Power supply for the circuit should not exceed 3 Volts.


COMPONENTS:
  • Resistor R1      ->       Emitter Loading
  • Resistor R2      ->       Base Biasing
  • Capacitor C1   ->       Frequency Generation
  • Capacitor C2   ->       Feedback
  • Capacitor C3   ->       Feedback
  • Capacitor C4   ->       Noise Reduction
  • Capacitor C5   ->       Coupling
  • Capacitor C6   ->       Coupling
  • Capacitor C7   ->       Decoupling
  • Transistor Q1   ->       Amplification
  • Inductor L1      ->       Frequency Generation
IMPORTANT POINTS:
For any jammer circuit, it’s essential to have three important sub circuits.
  • RF amplifier
  • Voltage Controlled Oscillator
  • Tuning circuit
These 3 circuits, when combined together form an efficient cell phone jammer circuit.

WORKING:

  • RF amplifier circuit comprises of the transistor Q1, capacitors C4, C5 and resistor R1. This RF circuit amplifies the signal generated by the tuned circuit. The amplified signal is given to the antenna through capacitor C6. It blocks DC and allows only the AC component of the signal to be transmitted.
  • When transistor Q1 is turned ON, the tuned circuit at the collector turns ON. The tuned circuit consists of capacitor C1 and inductor L1. This acts as an oscillator with zero resistance. It produces very high frequency with minimum damping.
  • When the circuit is ON, voltage is stored in the capacitor. Once the capacitor is completely charged, it allows charge to flow through the inductor. When current flows through the inductor, it stores magnetic energy corresponding to the voltage across the capacitor. At a certain point, the inductor reaches its maximum and the charge or voltage across the capacitor turns to zero.
  • Now the magnetic charge through the inductor decreases and the current charges the capacitor in opposite or reverse polarity. The process repeats and after a while, inductor charges the capacitor and becomes zero.
  • This process runs till internal resistance is generated and the oscillations stop. RF amplifier feed is given through capacitor C5 to the collector terminal before C6. The capacitors C2 and C3 generate pulses in random fashion (noise) at the frequency generated by the tuned circuit.
  • The RF amplifier boosts the frequency generated by the tuned circuit. The frequency generated by the tuned circuit and the noise signal generated by the capacitors C2 and C3 is combined, amplified and transmitted.

3 Ways Dimmer Switch Wiring Diagram

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Basic 3-Way Dimmers Switches
A 3-way dimmer switch is very similar to a regular 3-way toggle switch except for the electronic unit which performs the actual dimming function.
Pre wire Dimmer Switches
Most 3-Way dimmers come with pre-wired leads that are color coded and explained below. These dimmers are also known as wall dimmers and light dimmers.

Hydroelectric Power Plant

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The most common type of hydroelectric power plant is an impoundment facility. An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level.

All Phones Sim Card Sizes



Mini SIM: This SIM card has been around for many years now and can be found on older smartphones or certain feature phones even today. The size of the SIM card is pretty big and if phones like the iPhone 3GS and Nexus 4 are some examples of the phones that relied on the mini SIM card.
Micro SIM: The micro SIM is pretty much the standard these days for the majority of smartphones. Pretty much all Android smartphones at the moment accept the micro SIM as the SIM card of choice. It is noticeably smaller than the mini SIM and has helped to contribute to the creation of thinner smartphones. Phones such as the iPhone 4, iPhone 4S, Nexus 5, and Samsung Galaxy S5 are examples of phones that use the micro SIM.
Nano SIM: The nano SIM is currently the smallest SIM card available at the moment. At one point in time, there was a bit of contention between Apple and Nokia regarding the nano SIM in which Apple was looking to make the nano SIM the new standard in SIM cards.
The nano SIM is much smaller than the micro SIM and it pretty much leaves just the chip of the SIM card exposed, where the micro and full-sized SIM cards still had a bit of plastic surrounding the edge.
Apple has since adopted the nano SIM as the standard on its mobile devices starting with the iPhone 5, and Nokia has since followed suit despite their initial reluctance with phones like the Nokia Lumia 1520 and Nokia Lumia Icon, just to name a few. Android OEMs such as HTC have also started to use the nano SIM with the HTC One M8.
Embedded SIM: This is another type of SIM although its use is aimed more at M2M applications rather than consumer products like smartphones or tablets.
At one point in time it was rumored that Apple had considered the idea of incorporating embedded SIMs into its products in which customers could simply choose their carrier at an Apple store and have it activated there and then.
Usage of embedded SIMs can be found in vehicles where carriers such as Vodafone have supplied embedded SIMs to the upcoming 2015 Audi and Volkswagen models.

Design An EEG at home


This is my design for a DIY saline based electrode set. I chose the saline approach because it is more convenient than using conventional electrodes. Conventional electrodes require a conductive paste which can be expensive, time consuming and messy.
Commercial electrodes are made from precious metals because they conduct well and do not react (ie. rust). I'm hoping the saline approach will counter any impedance gained from using inexpensive metals.
This is an ongoing experiment. Once I have some comparative data I will be able to tell you how well they work. They are sensitive enough to measure ocular (eye) movements which is a good start.
There is one design flaw however. The small screws in the coax plugs rust.


COMPONENTS:

        ITEM                                             Cat no.       AMOUNT      
  • Head band                                                                     1                  
  • Elastic                                                                         30cm           
  • 5 core shielded cable                              W2040              2m               
  • Twin core shielded audio cable                 W2034              1m               
  • Male plastic coax plug                            P2021                5                  
  • Sponge ear plugs                                                         packet of > 5      
  • Heat shrink tubing 4.8mm                       W4104             1.2m            
  • Heat shrink tubing 6.4mm                       W4104             1.2m            
  • Table salt                                                                       1                  
  • 5 pin DIN plug and socket *                                             1                           
  • Insulation tape *                                                             1                                        
HOW TO MAKE ELECTRODES AT HOME:
  • The electrodes are made from coax connectors and ear plugs (sponge).
                                                               

  • The pin assembly inside the plug is removable and is clamped onto the end of the cable with a screw.


  • The pin is inserted into a hole in the back of the sponge. You can use something like a bamboo skewer to prepare the hole.
  • The plug is then reassembled through the head band.
  • The sponge is pre-soaked for at least a day in a saline solution.
  • I also use one of these for my DRL (driven right leg).
CABLING:

Initially I considered using audio jacks to connect my cables to the eeg but decided against it because they are easy to snap (especially when somebody walks away while still wearing the electrodes).
Instead I opted to use a 5 pin din connector.
I split the cable progressively down from 5 pair to a single core for each electrode. I was careful to continue the shielding and used heat shrink and tape to insulate the soldered joins.


HEAD BAND:
  • The head band is a wide black plastic ladies hair band purchased from a chemist.
  • I did not own a drill bit large enough to fit the coax plugs so I used the biggest bit on hand and filed the rest out with a circular rasp.

  • It is important to remember that the head band rests a good 3cm (1/2 inch) away from the scalp when the electrodes are inserted. Take this into consideration when choosing where to drill your holes.
  • I used the standard international 10/20 system positions.
  • The driven right leg is placed in the middle of the scalp (CZ).



SALINE SOLUTION:

The saline is prepared by mixing a whole heap of table salt and water (I don't know how much is optimum, but more is better than less). It is best to use distilled water if you can.

For Any Instruction you can ask me any time by commenting below......


 
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