Other disadvantages are: -

1. They can not store much information.
2. They can not be read from a distance.
3. They lose their data if placed under magnetic field or even on scratching.
4. There is no security to protect card data whereas in our card this is achieved with the provision of passwords.
5. There is no Re-Writable memory for temporary data storage such as railway reservation ticket.

The above-mentioned shortcomings are technical but there are user related problems also when one needs to handle a large number of cards at a time to obtain diverse information (Atm, Credit card, License, Voter Id. etc.). The user is highly inconvenienced as he is required to change over the cards frequently, so we have designed a card which combines information contained in a variety of cards. Since data is transferred using IR sensors so in many applications we can identify the user from a distance. We can also lock the data stored in card by using various passwords. Card can also store specific data in RAM for temporary use such as railway reservation, air bookings etc. we can also use the cards in automatic doors fitted with sensors which read the card from some distance and open the door only for authorized card holders.

BLOCK DIAGRAM

1. Card Unit: -

Block diagram of card unit

IR Sensors: - We are using here the infrared light as communication medium because of its low cost and better reception in short range communication. To make the receiver perform better it is designed to recognize the switching IR light of particular wavelength.

The wave length and switching frequency can be taken from the manufacturers data sheets

Buffer Amplifier: – The O\P of sensor does not have the current capacity to drive the microcontroller hence we use the buffer amplifier between sensor and micro controller.

Buffer Amp 2: – This section provides the current gain to signals coming from microcontroller.

Astable M.V.: – It generates the switching waveform to switch the IR LED on & off the frequency of the M.V. depends upon the sensor used.

Micro controller: – This is the part of card which stores the data in its EEPROM & also performs all the operations required for testing the incoming data & to decide the response of received data. It also controls the mode of serial communication and speed of communication.

2. PC Unit: –

Block diagram of PC Unit

For the pc unit all the blocks are same but instead of using microcontroller we use serial port of pc which follows the RS232 standard hence we use a Level Converter between port and Buffer Amp.
The first level converter converts the TTL signals in to RS232 signals & second level converter converts the RS232 signals to TTL signals. The conversion is necessary because the sensors & M.V. works on TTL logic.

3. Door unit: –

Block diagram of door unit

Here we implemented one utility of the card by opening the cabin door (in office) automatically as the authorized person come up to a certain distance from door, by reading his or her card from distance.

Now if the cards data does not match with door unit it sends the persons card number to PC & ask to open the door if operator press Y the door unit will open the gate.

To complete the door unit we require combining the following section as shown in block diagram.
Now we see that all the sections as same as we have discussed in previous blocks except that Relay & Beeper section. So we will discuss only this section. The door unit performs the two work one send data to call the specific data from card & read data from card through sensor. Now if persons card no does not match with unit it sends the pulses the beeper unit which produce the intermittent beep sound to indicate that door is not opened.

Pin configuration of a seven segment display:

LED’s are basically of two types:

1. Common Cathode (CC)
   All the 8 anode legs uses only one cathode, which is common.
2. Common Anode (CA)
   The common leg for all the cathode is of Anode type.

For the discussion purpose, we use CC LED, where by just reversing the logical voltages we can implement the same for CA LED also.

In a CC LED, all the 8 legs (‘a’ through ‘h’) are of anode type and the common cathode will be connected to the GND of the supply. By energizing any of the legs with +5 Volts will lead to switch the correspondent segment ON. In the microprocessor binary system, 0Volts will be considered as Binary 0, and 5Volts will be considered as Binary1. Considering these two condition, we can make an arrangement as the microcontroller gives OUT the 0s and 1s through its ports, which is connected to the 8 legs of the LED. Of course, we can control the Port Output; implicitly we can Switch-ON required legs of the display.

There 2 methods of interfacing LED with the Microcontroller Intel 8051/8951.

1. Using lookup table. This uses 7 output pins of microcontroller
2. Using 7447 decoder. This method uses 4 output pins of microcontroller

The difference between the two main methods is simple and clear. In both the cases, microcontroller communicates with external world through its ports. But, in the 1st case, we connect all the 8 pins of the port directly to the LED and control the voltage through the ports manually to display the desired number. But, in the second case, we send the BCD of the number that we wanted to display to a middleware IC 7447, the BCD to LED code converter, which by itself gives out the correspondent 7 segment codes to the LED.

Here we explain using lookup table. Click here for the method “using 7447 decoder”

Using 7447 decoder:

The IC7447 is a BCD to 7-segment pattern converter. This setup is the advanced form of the <previous> setup where we entered the patterns manually to display the desired character. Here in this case, the IC7447 takes the Binary Coded Decimal (BCD) as the input and outputs the relevant 7 segment code. We connect first four pins of the microcontroller Port 2  to the 7447 and the Output 8 pins of 7447 to the 8 legs of the LED as shown in the figure. Te circuit diagrams are shown below, the first figure is interfacing the CA LED where as the second is of CC LED. The number required to display is sent as the lower nibble of the Port 2 of the Microcontroller. The 7447 converts the four input bits (BCD) to their corresponding 7-segment codes. The outputs of the 7447 are connected to the 7-segment display.

Circuit diagram for interfacing Common Anode 7-Segment Display

Circuit diagram for Common Cathode 7-Segment Display

Program:

This program displays characters 0 through 9 on seven-segment display 
using IC 7447 as the middle wear.
 
  again: mov a,#00h                  ; Start form zero
     up:  mov p2, a                  ; Move to Port 2
          mov r3,#255                ; Delay
     D1:  mov r1,#255
      D:  djnz r1,D
          djnz r3,D1
          inc a
          cjne a,#0ah,up
          sjmp again

Block diagram of the project:

Some photographs of this model:

Robotic car model

Robotic car model

Project Description:

Keyboard section:

There are six switches in this section. They are

1. Turn left.
2. Turn right.
3. Stop.
4. About turn.
5. Park left.
6. Park right.

Circuit diagram of keyboard is shown bellow.

Keyboard circuit of the Robotic car

Car section:

There are many sub sections in this section. They are

Motor:

We are using a 5V dc motor to drive the vehicle. The speed of the vehicle and its strength is controlled by the proper use of pulley. The rear wheel of the vehicle is connected to this motor through a pulley. This motor is meant for moving the vehicle both in forward and backward direction. Microcontroller (8051) controls the forward and backward movement of the vehicle in the following manner:

Circuit diagram of Motor connection

Here in the above circuit, T1, T2, T3, T4 are the NPN power transistor (2N3055). A0, A1, A2, A3 are the signals coming from the micro controller. With the specific combination of A0, A1, A2, A3 we can change the direction of rotation of motor as follows:

Case I: When   A0=high; A3=high; & A1=low; A2=low
The motor rotates in clockwise direction

Case II: When   A0=low; A3=low; & A1=high; A2=high
The motor rotates in anti-clockwise direction

Case III: When   A0=low; A3=low; A1=low; A2=low
The motor stops the rotation.

LCD pin descriptions

LCD pin desciptions

Vcc, Vss, and VEE:

While Vcc and Vss  provide  +5V and ground, respectively, VEE  is used for controlling LCD contrast.

RS – register select:

There are two very important registers inside the LCD. The RS pin is used for their selection as follows. If RS = 0, the instruction command code register is selected, allowing the user to send a command such as clear display, cursor at home, etc. If  RS = 1 the data register is selected, allowing the user to send data to be displayed on the LCD.

R/W – read/write:

R/W input allows the user to write information to the LCD or read information from it. R/W = 1 when reading; R/W =0 when writing.

E – enable:

The enable pin is used by the LCD to latch information presented to its data pins. When data is supplied to data pins, a high to low pulse must be applied to this pin in order for the LCD to latch in the data present at the data pins. This pulse must be a minimum of 450 ns wide.

D0 – D7:

The 8 bit data pins, D0 – D7, are used to send information to the LCD or read the contents of the LCD’s internal registers.

To display letters and numbers, we send ASCII codes for the letters A – Z, a – z, and numbers 0 – 9 to these pins while making RS = 1.

There are also instructions command codes that can be sent to the LCD to clear the display or force the cursor to the home position or blink the cursor. Table below lists the instruction command codes.

LCD Commands table

We also use RS = 0 to check the busy flag bit to see if the LCD is ready to receive information. The busy flag is D7 and can be read when R/W =1 and RS = 0, as follows: if R/W =1, RS =0. When D7 = 1(busy flag = 1), the LCD busy taking care of  internal operations and will not accept any new information. When D7 = 0, the LCD is ready to receive new information. Note: It is recommended to check the busy flag before writing any data to the LCD.

Example programs are given in the next page.