Aim of this project is to control the unmanned rail gate automatically using embedded platform. Today often we see news papers very often about the railway accidents happening at un- attended railway gates. Present project is designed to avoid such accidents if implemented in spirit.
This project is developed in order to help the INDIAN RAILWAYS in making its present working system a better one, by eliminating some of the loopholes existing in it. Based on the responses and reports obtained as a result of the significant development in the working system of INDIAN RAILWAYS, This project can be further extended to meet the demands according to situation.
This can be further implemented to have control room to regulate the working of the system. Thus becomes the user friendliness.
In this project AT89c51 Micro controller Integrated Chip plays the main role.
The program for this project is embedded in this Micro controller Integrated Chip and interfaced to all the peripherals.
The timer program is inside the Micro controller IC to maintain all the functions as per the scheduled time. Stepper motors are used for the purpose of gate control interfaced with current drivers chip ULN2003 it’s a 16 pin IC.
• There is no time lag to operate the device
Fig 1. 1.1 Block Diagram of AUTOMATIC RAILWAY GATE
AT89C51 is a 40 pin dip micro controller, can be divided in to four ports, it is driven by 5v supply. In this project Atmel 89c51 Micro controller Integrated Chip plays the main role. The program for this project is embedded in this Micro controller Integrated Chip and interfaced to all the peripherals. The timer program is inside the Micro controller IC to maintain all the functions as per the scheduled time.
The Light dependent resistor is interfaced to Atmel 89c51 Micro controller to display the message, stepper motors are used for the purpose of gate control interfaced with current drivers chip ULN2003. ULN2003 is a current driver chip used for supply control to the stepper motor; it is a 16 pin dip. Here a stepper motor is used for controlling the gates. A stepper motor is a widely used device that translates electrical pulses into mechanical movement. They function as their name suggests – they “step” a little bit at a time. Steppers don’t simply respond to a clock signal.
They have several windings which need to be energized in the correct sequence before the motor’s shaft will rotate. Reversing the order of the sequence will cause the motor to rotate the other way.This project work aims at the design, development, fabrication and testing of working model entitled “Automatic Railway Gate Controller”. It is basically related to Radio communication and signalling system. An Automatic Railway gate controller is unique in which the railway gate is closed and opened or operated by the Train itself by eliminating the chances of human errors.The largest public sector in India is the Railways.
The network of Indian Railways covering the length and breath of Indian Railways covering the length and breath of our country is divided into nine Railway zones for operational convenience. The railway tracks criss-cross the state Highways and of course village road along their own length. The points or places where the Railway track crosses the road are called level crossings. Level crossings cannot be used simultaneously both by road traffic and trains, as this result in accidents leading to loss of precious lives.
A computer-on-a-chip is a variation of a microprocessor, which combines the processor core (CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chip is called the microcomputer whose proper meaning is a computer using a (number of) microprocessor(s) as its CPUs, while the concept of the microcomputer is known to be a microcontroller. A microcontroller can be viewed as a set of digital logic circuits integrated on a single silicon chip. This chip is used for only specific applications.
A designer will use a Microcontroller to
1. Gather input from various sensors
2. Process this input into a set of actions
3. Use the output mechanisms on the Microcontroller to do something useful 4. RAM and ROM are inbuilt in the MC.
5. Multi machine control is possible simultaneously.
6. ROM, EPROM, [EEPROM] or Flash memory for program and operating parameter storage. Examples:
8051, 89C51 (ATMAL), PIC (Microchip), Motorola (Motorola), ARM Processor, Applications: Cell phones, Computers, Robots, Interfacing to two pc’s.
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4Kbytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pin out.
The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer, which provides a highly-flexible and cost-effective solution to many embedded control applications.
• 4Kbytes of Flash memory, 128 bytes of RAM.
• 32 I/O lines, two 16-bit timer/counters.
• a five vector two-level interrupt architecture, a full duplex serial port,
• on – chip oscillator and clock circuitry.
• In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes.
• The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning.
• The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.
Fig 2.2.1 Pin diagram of AT89C51 MICROCONTROLLER
VCC: Supply voltage.
The AT 89c51 micro controller is a 40-pin IC. The 40th pin of the controller is Vcc pin and the 5V dc supply is given to this pin. This 20th pin is ground pin. A 12 MHZ crystal oscillator is connected to 18th and 19th pins of the AT 89c51 micro controller and two 22pf capacitors are connected to ground from 18th and 19th pins. The 9th pin is Reset pin.
Port 0: Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull-ups are required during program verification.
Port 1: Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 1 also receives the low-order address bytes during Flash programming and verification.
The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.
The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of various special features of the AT89C51 as listed below:
Port Pin Alternate Functions
P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0 (external interrupt 0)
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR (external data memory write strobe)
P3.7 RD (external data memory read strobe)
Table 2.2.1 Port3 description of AT89C51 Microcontroller
A high on this pin for two machine cycles while the oscillator is running resets the device.
ALE/PROG: Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes.
Note, however, that one ALE pulse is skipped during each access to external Data Memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the micro controller is in external execution mode.
PSEN: Program Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.
EA/VPP: External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.
XTAL1: Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2: It is the output from the inverting oscillator amplifier.
A stepper motor (or step motor) is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. The motor’s position can be controlled precisely, without any feedback mechanism (see open loop control). Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated). [pic]
Fig no: 3.1.1 Basic stepper motor
Fundamentals of Operation:
Stepper motors operate differently from normal DC motors, which rotate when voltage is applied to their terminals. Stepper motors, on the other hand, effectively have multiple “toothed” electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller.
To make the motor shaft turn, first one electromagnet is given power, which makes the gear’s teeth magnetically attracted to the electromagnet’s teeth. When the gear’s teeth are thus aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those slight rotations is called a “step,” with an integral number of steps making a full rotation. In that way, the motor can be turned by a precise angle.
Stepper motors are constant power devices. As motor speed increases,
torque decreases. The torque curve may be extended by using current limiting drivers and increasing the driving voltage. Steppers exhibit more vibration than other motor types, as the discrete step tends to snap the rotor from one position to another. This vibration can become very bad at some speeds and can cause the motor to lose torque.
The effect can be mitigated by accelerating quickly through the problem speed range, physically damping the system, or using a micro-stepping driver. Motors with a greater number of phases also exhibit smoother operation than those with fewer phases. Open-loop versus closed-loop commutation
Steppers are generally commutated open loop, i.e. the driver has no feedback on where the rotor actually is. Stepper motor systems must thus generally be over engineered, especially if the load inertia is high, or there is widely varying load, so that there is no possibility that the motor will lose steps. This has often caused the system designer to consider the trade-offs between a closely sized but expensive servomechanism system and an oversized but relatively cheap stepper.
A new development in stepper control is to incorporate a rotor position feedback (eg. an encoder or resolver), so that the commutation can be made optimal for torque generation according to actual rotor position. This turns the stepper motor into a high pole count brushless servo motor, with exceptional low speed torque and position resolution. An advance on this technique is to normally run the motor in open loop mode, and only enter closed loop mode if the rotor position error becomes too large — this will allow the system to avoid hunting or oscillating, a common servo problem.
There are three main types of stepper motors:
• Permanent Magnet Stepper
• Hybrid Synchronous Stepper
• Variable Reluctance Stepper
There are two basic winding arrangements for the electromagnetic coils in a two phase stepper motor: bipolar and unipolar. Unipolar motors:
A unipolar stepper motor has logically two windings per phase, one for each direction of magnetic field. Since in this arrangement a magnetic pole can be reversed without switching the direction of current, the commutation circuit can be made very simple (e.g. a single transistor) for each winding. Typically, given a phase, one end of each winding is made common: giving three leads per phase and six leads for a typical two phase motor. Often, these two phase commons are internally joined, so the motor has only five leads. [pic]
Fig 3.2 Unipolar stepper motor coils In the construction of unipolar stepper motor there are four coils. One end of each coil is tide together and it gives common terminal which is always connected with positive terminal of supply. The other ends of each coil are given for interface. Specific color code may also be given. Like in my motor orange is first coil (L1), brown is second (L2), yellow is third (L3), black is fourth (L4) and red for common terminal. By means of controlling a stepper motor operation we can
1. Increase or decrease the RPM (speed) of it
2. Increase or decrease number of revolutions of it
3. Change its direction means rotate it clockwise or anticlockwise To vary the RPM of motor we have to vary the PRF (Pulse Repetition Frequency). Number of applied pulses will vary number of rotations and last to change direction we have to change pulse sequence. So all these three things just depends on applied pulses. Now there are three different modes to rotate this motor 1. Single coil excitation
2. Double coil excitation
3. half coil excitation
Unipolar stepper motors with six or eight wires may be driven using bipolar drivers by leaving the phase commons disconnected, and driving the two windings of each phase together [diagram needed]. It is also possible to use a bipolar driver to drive only one winding of each phase, leaving half of the windings unused [diagram needed].
Bipolar motors have logically a single winding per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H-bridge arrangement. There are two leads per phase, none are common. Static friction effects using an H-bridge have been observed with certain drive topologies Because windings are better utilized, they are more powerful than a unipolar motor of the same weight.
• Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems. • In the field of linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems. • In floppy disk drives, flatbed scanners, computer printers, plotters and many more devices.
The ULN2003 is a high-voltage, high current Darlington drivers comprised of seven NPN Darlington pairs. Features:
1) Output current (single output) 500mA MAX.
2) High sustaining voltage output 50V MIN.
3) Input compatible with various types of logic.
➢ Lamp and display(LED)drivers
Fig:4.2.1 Pin diagram of ULN2003
• No. of pins:16
• Temperature, Operating Range:-20°C to +85°C
• Transistor Polarity:NPN
• No. of Transistors:7
• Case Style:DIP-16
• Min operating temperature:-20°C
• Max operating temperature:85°C
• Base Number:2003
• Max Output current:500mA
• IC Generic Number:2003
• Input Type:TTL, CMOS 5V
• Output Type: Open Collector
• Transistor Type: Power Darlington
• Max Input Voltage:5V
• Max Output voltage:50V
Fig 4.2.2 Pin configuration of ULN 2003 The ULN2001A, ULN2002A, ULN2003 and ULN2004Aare high Voltage, high current
Darlington arrays each containing seven open collector Darlington pairs with common emitters. Each channel rated at 500mAand can withstand peak currents of 600mA.Suppressiondiodesare included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout.
These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors; LED displays filament lamps, thermal print heads and high power buffers. The ULN2001A/2002A/2003A and 2004A are supplied in 16 pin plastic DIP packages with a copper lead frame to reduce thermal resistance. They are available also in small outline package (SO-16) as ULN2001D/2002D/2003D/2004D.
The circuit below is a ‘Darlington Pair’ driver. The first transistor’s emitter feeds into the second transistor’s base and as a result the input signal is amplified by the time it reaches the output. Darlington pairs are back to back connection of two transistors with some source resistors.
Fig: 4.2.3 The Darlington pair connection of transistor.
The important point to remember is that the Darlington Pair is made up of two transistors and when they are arranged as shown in the circuit they are used to amplify weak signals. The amount by which the weak signal is amplified is called the ‘GAIN’. .
These amplifiers are designed to specifically to operate from a solitary supply over a wide range of voltages. Also can function when the difference between the two supplies is 3V to 30V and VCC is at least 1.5V more positive than the input common mode voltage.
Fig: 5.1 Pin diagram of LM324
V+ = Supply voltage
GND = Gnd (0V) connection for supply voltage
Input(s) = Input to Op-Amp
Output(s) = Output of Op-Amp
• Supply voltage V + : +32VDC or +16VDC
• Differential Input Voltage : 32VDC
• Input Voltage : -0.3VDC to +32VDC
• Power Dissipation : 570mW
• Operating Temperature : 0 to 70C degree
• Output Current Source : Typical 40mA
• Output Current Source : Typical 40mA
• Output Current Sink : Typical 20mA
• Input Offset Voltage : Typical 2.0mVDC
• Operates on a single supply over a range of voltages Unique features:
In the linear mode, the input common-mode voltage range includes ground and the output voltage can also swing to ground, even though operated from only a single power supply voltage. The unity gain crossover frequency and the input bias current are temperature-compensated. Applications:
• In Transducer amplifiers.
• DC amplification blocks and conventional operations.
This practical is about using a light dependent resistor (LDR) as a sensor. The LDR must be part of a voltage divider circuit in order to give an output voltage, Vout , which changes with illumination.
A light dependent resistor is a resistor whose resistance decreases with increasing incident light intensity. It can also be referenced as a photo conductor. An LDR is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance. An LDR device can be either intrinsic or extrinsic.
An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire band gap. Extrinsic devices have impurities, also called do pants, and added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction. [pic]
Fig 6.1.1 Light dependent resistor
Note that an LDR responds in an extremely non-linear way to the light intensity. The resistance of a LDR changes from a few meg-ohms in dim light to a few kilo ohms in bright light (maybe even a few ohms depending upon the light intensity and LDR used.). So I would suggest that u first connect the LDR as VCC —— LDR——- LM 324 ——– Microcontroller. and plot the voltage across the 1K resistor with respect to different light intensities on the LDR.Then connect this voltage output to a ADC via a simple non-inverting op-amp amplifier and connect the ADC to the Microcontroller.
• Camera light meters, street lights, clock radios, alarms, and outdoor clocks. • They are also used in so dynamic compressors together with a small incandescent lamp or light emitting diode to control gain reduction. • Lead sulfide and Idiam sulfide LDRs are used for the mid infrared spectral region.Ge: Cu photoconductors are among the best far-infrared detectors available, and are used for infrared astronomy and infrared spectroscopy.
Fig no:7.1.1 ULN2003 is interfaced with the stepper motor
ULN2003 is a 16 pin dip. Its connections can be explained as follows
First 4-pins of chip are connected to microcontroller pin at 37-40 pins and second at 21-24 pins. And 8th pin of chip is grounded. A stepper contains 5 terminals, 4 winding wires and a power supply wire. These 4 winding wires are connected to chip and another to supply. in this circuit too the four pins “Controller pin 1”,2,3 and 4 will control the motion and direction of the stepper motor according to the step sequence sent by the controller.
fig no: 7.2.1 stepper motor interfacing with AT89C51 using ULN2003. The interfacing of stepper motor consists of several parts like AT89C51 microcontroller, stepper motor, and ULN2003 current driver chip. This can be used in this project for the purpose of gate control . For the gate control a 12v stepper motor is used.ULN2003 is a current driver chip used for supply control to the stepper motor; it is a 16 pin dip.AT89C51 is a 40 pin dip micro controller, can be divided in to four ports, it is driven by 5v supply.
Fig no: 7.2.2 The block diagram of stepper motor interfacing Here a stepper motor is used for controlling the gates. A stepper motor is a widely used device that translates electrical pulses into mechanical movement. They function as their name suggests – they “step” a little bit at a time. Steppers don’t simply respond to a clock signal. They have several windings which need to be energized in the correct sequence before the motor’s shaft will rotate. Reversing the order of the sequence will cause the motor to rotate the other way.
Fig 7.3.1 Interfacing of LM324 with AT89c51 Microcontroller
The LM324 integrated circuit is a Quad operational amplifier(op-amp).The device has four individual Op-amp circuits housed in a single package.
A variable regulated power supply,also called a variable bench power supply,is one which you can continuously adjust the output voltage to your requirements. Varying the output of the power supply is recommended way to test a project after having double checked parts placement against circuit drawings and the parts placement
This type of regulation is ideal for having a simple variable bench power supply. Actually this is quite important because one of the first projects a hobbyist should undertake is the construction of a variable regulated power supply. While a dedicated supply is quite handy e.g 5V or 12V,it’s much handier to have a variable supply on hand, especially for testing.
Most digital logic circuits and processors need a 5 volt power supply. To use these parts we need to build a regulated 5 volt source. Usually you start with an unregulated power to make a 5 volt power supply, we use a LM7805 voltage regulator IC (Integrated Circuit).
The IC is shown below. [pic]
Fig: 8.1.1 LM 7805 block diagram
Fig: 8.1.2 Pin representation of LM 7805
The LM7805 is simple to use. You simply connect the positive lead of your unregulated DC power supply(anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to the Common pin and then when you turn on the power, you get a 5 volt supply from the Output pin.
• Brief description of operation: Gives out well regulated +5V output, output current capability of 100mA. • Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot. • Circuit complexity: Very simple and easy to build. • Circuit performance: Very stable +5V output voltage, reliable operation • Availability of components: Easy to get, uses only very common basic components. • Design testing: Based on datasheet example circuit, I have used this circuit successfully as part of many electronic projects. • Applications: Part of electronics devices, small laboratory power supply
1. Program for gate control:
void MSDelay (unsigned int value);
void main ()
if (sense1==1 && sense2!=1)
for (i=0; i
void MSDelay (unsigned int value)
unsigned int x,y;
1. Kenneth.J.Ayala”The 89C51 Microcontroller Architecture programming and Applications”, Pen ram International.
2. D.Roychoudary and Sail Jain”L.I.C”, New Age International.
3. “Principles of Electronics” by V.K.MEHTA.
4. “Communication Systems” by Simon Hawkins.
5. “Electrical Technology – vol. 2- B.L. Theraja.
2.http://www.atmel.com/dyn/resources/prod_documents/doc0265.pdf 3. http://www.ortodoxism.ro/datasheets/texasinstruments/max232.pdf
LIGHT DEPENDANT RESISTOR
1 L 14
2 M 13
3 3 12
4 2 11
5 4 10
1 u 9
2 l 10
3 n 11
4 2 12
5 0 13
6 0 14
7 3 15
1 vcc 40
6 A 35
7 T 34
8 8 33
9 9 32
10 C 31
11 5 30
12 1 29
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