buying component

no	quantity	components	Ilustrate
1	1	PIC  16F877A
2	3	RFID keychain
3	1	AC/DC ADAPTER & female jack Description: 12Vdc , 2Amps
4	2	IR sensor
5	1	MOTOR DRIVER (L298N Dual-H Bridge DC Motor Driver IC)
6	2	DC MOTOR  Description: 4.5Vdc, 50rpm
7	1	Xtal 4MHz
8	1	LCD 16 bit
9	1	D-sub socket 9pin communication
10	1	RFID reader

methodology

Block diagram



updated block diagram

flowchart

IR sensor concept

figure: left side when have obstacle, right side when free air space

wiegend conversion discussion

A bit is a logical term for the difference between on/off, true/false, yes/no, etc. All digital electronics operate off of bits. You computer computes with millions of bits. Think of them as switches, that turn off and on. Different paths occur when certain switches get turned off and on. A bit has two states, on and off. When it is on, it is considered a (1). When it is off, is considered a (0). If you string several together, they form bytes, words, etc. That is as far as I will go for now. We will focus on the bits for Wiegand data.

If you take the number of 25 and convert it to bits you will get 11001.

26bit Wiegand data is formed using 24bits of data, and two parity bits.

The facility code is made up of 8 bits. This allows the facility code to have a range of 0-255.

The device number uses 16 bits. This allows the device to have a range of 0-65535.

Although there are many combinations of codes that can be used, many manufactures have created larger bit rates to increase the number of facility codes and device numbers.

In this first image, I have a screen capture from an oscilloscope attached to the two data lines of a 26bit card reader.

The voltage normally rests at 5v. When a card is read, the card reader sends the 26 bits. In this demonstration, the first bit is a 1. The Data 1 (white wire, D1) line falls close to 0v briefly. The next two bits are zeros. The Data 0 (green wire, D0) line falls close to 0v twice briefly. This continues until all 26 bits are sent in this manner. This is how Wiegand data is transferred.

The bits are numbered 1 – 26 left to right.

Bit 1 is an even parity bit. Put simply this is an error correction bit. If the bits 2-13 have an odd number of bits (1’s), then this bit is on to make the first 13 bits even.

The opposite is true with the 26th odd bit. If the bits 14-25 have an even number of bits (1’s), then this bit is on to make the last 13 bits odd.

These parity bits may be used in certain access controllers. DoorKing and Linear ignore these parity bits. This is demonstrated by wiring the Wiegand device backwards. If you swap the data 1 and data 0 wires you reverse the order of the bits. Thus, a seemingly random number is shown. If the parity bits were used for error checking, then the data would be rejected.

RFID description

RFID-based parking system introduction 

Radio-frequency identification(RFID) is an automatic identification method wherein the data stored on RFID tags or transponders is remotely retrieved.The RFID tag is a device that can be attached to or incorporated into a product, animal. or person for identification and tracking using radio waves. Some tags can be read from several meters away, beyond the line of sight of the reader. RFID  technology is used in vehicle parking systems of malls and buildings .


The system normally consists of a vehicle counter, sensors, display board, gate controller, RFID tags and RFID reader. Presented here is an automatic vehicle parking system using PIC 16F877A microcontroller.

Basically, an RFID system consists of an antenna or coil, a transceiver (with decoder) and a transponder (RF tag) electronically programmed with unique information.There are many different types of RFID systems in the market. These are categorized on the basis of their frequency ranges. Some of the most commonly used RFID kits are low-frequency (30-500kHz), mid-frequency (900kHz-1500MHz) and high-frequency (2.4-2.5GHz).

RFID antenna. Figure 1 shows the internal diagram of a typical RFID antenna. The  antenna emits radio signals to activate the tag and read/write data from/to it. It is the conduit between the tag and the transceiver, which controls the system’sdata acquisition

figure 1: internal structure of RFID tag

how (passive RFID)RFID tag can transfer data by no having a battery?

RFID tag (passive) will get a supply from a RFID reader. when RFID reader on, so RFID reader will transfer a magnetic field by copper coil(RFID antenna) to the RFID tag when it touch it or near by in some range. when RFID receive a EMF from RFID reader , then it will go to the chip and from chip RFID tag will transfer back RFID reader that case we call it as back scatter. both RFID tag and reader have antenna (copper coil) it same as wireless power transfer.

RFID wiegand input format description:

Wiegand protocol provides 2 lines for data transfer. A pulsed transition on the DATA1 line indicates a logic 1 bit, while a pulsed transition on the DATA0 line indicates a logic 0 bit.  In their idle state both lines are held high. During data transfer the appropriate logic line will pulse low for 50us followed by period of 2ms where both lines are held high.

In this fashion each bit it transmitted in sequence until all bits are sent.  The end of the transmission is signaled by both lines being held high for more than 50ms.

 Figure below show an example of the timing sequence for wiegand protocol

new Literature Review

figure1: RFID basic concept

RFID acts as a signal mirror. For centuries we have known how to communicate messages with just a mirror by flashing the sun reflection to the direction of the recipient. The flashes are sequenced to represent a code known by the recipient, for example Morse code that communicates intelligence without the necessity of an infrastructure that establishes physical contact such as telegraph line. So, messages can be sent through air simply by reflecting radiated sunlight. That is the basic idea behind RFID, except that instead of using radiated sunlight as our communication medium, we reflect radio waves as shown in Figure 1. The basic theory underlying RFID technology has been discovered that the introduction of a conductive material into an electric or magnetic field could alter the field characteristics. That occurs because the conductive material both absorbs and reflects the energy in the field. If the field is a radio frequency or RF, the conductive material is capable of imparting a reflection of the source field radiation. RFID technology takes advantage of that characteristic by manipulating the sequence and rate at which that reflection occurs, called modulation. RFID tags are designed to deliberately reflect the source RF in sequences that are interpreted as information in the form of digital data

Radio-frequency identification (RFID) is the wireless non-contact use of radio-frequency electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information. Some tags are powered by and read at short ranges (a few meters) via magnetic fields (electromagnetic induction). Others use a local power source such as a battery, or else have no battery but collect energy from the interrogating EM field, and then act as a passive transponder to emit microwaves or UHF radio waves (i.e., electromagnetic radiation at high frequencies). Battery powered tags may operate at hundreds of meters. Unlike a barcode, the tag does not necessarily need to be within line of sight of the reader, and may be embedded in the tracked object