Live-Steam-Train-Model M.Sc-II (Electronics) Department of Electronic ScienceAKI’S Poona College of Arts, Science & Commerce Camp, Pune-01 (India)
We know that the railway network of India is the biggest in southAsia and perhaps the most complicated in all over the world. There are somany different types of trains local, fast, super fast, passenger, goods…. etc.and they’re so many multiple routs. Although the time table is perfect it isnot at all possible to maintain it. And that’s why the train accidents arebecoming more and more usual. So why not we add a kind of intelligence tothe train engines itself so that it tries to avoid accidents. The idea is whenever engine observes a red signal on its track it willstart decreasing its speed gradually and stops automatically at somedistance from the signal pole. After then when it gets green signal the drivercan manually start the train and go on. In the mean time when train hasnot stopped yet and a red signal becomes green then it crosses the signalpole with low speed and then driver can slowly increase the speed. So nowbefore the driver observes the red signal the engine itself observes it andautomatically starts decreasing speed and then stops. The driver can feelrelax in driving because he doesn’t have to take care about red signal. Evenif he forgets to take any action on red signal then also we can avoidaccidents by the implementation of this idea.
The block diagram consists of 2 unit Transmitter Receiver In this project the IR signals is received by the “TSOP” which acts as the interrupt given to the microcontroller, thus controlling the speed of the train.
Figure gives the block diagram of power supply. Every block diagram consists of the following blocks: AC INPUT TANSFORMER RECTIFIER FILTER VOLTAGE REGULATOR
As shown ac power supply 230 v is given to transformer as input. The used is step down which provides the output 24 V. It also isolate transformer is the circuit from the main power supply. The output of transformer is given to rectifier(ac to dc). The main function of the filter is to remove the ac components(called ripples) present in the output supplied by the rectifier. The main function of Voltage regulator is to keep the output constant even if there is change in the input. Zener diodes and transistors are used for voltage regulation. The output of voltage regulator is given to the load.
It is a electronic circuit that generates a high voltage level(HVL) and low voltage level(LVL) but neither the HVL nor LVL is permanent. If we use ic555 the HVL is +5v and the LVL is -5v. An astable multivibrator can be produced by adding resistors and a capacitor to the basic timer IC. The timing during which the output is either high or low is determined by the externally connected two resistors and a capacitor.
In figure, when VOUT is high, the discharging transistor is cut--off& the capacitor C begins charging toward VCC through resistances RA& RB. The charging time constant is (RA + RB) C. Eventually, the threshold voltage exceeds +2/3 VCC, thecomparator 1 has a high output & triggers the flip-flop so that its Q ishigh & the timer output is low. With Q high, the discharge transistor saturates & pin 7 grounds sothat the capacitor discharges through Resistance RB with adischarging time constant RB C. With the discharging of capacitor, trigger voltage at invertinginput of comparator 2 decreases. When it drops below 1/3VCC, the output of comparator 2goes high & this reset the flip-flop so that Q is low & the timer outputis high. This proves the auto-transition in output from low to high & thento low as, illustrated in figures. Thus the cycle repeats.
An infrared emitter is an LED made from gallium arsenide, which emits near-infrared energy at about 880nm. The infrared phototransistor acts as a transistor with the base voltage determined by the amount of light hitting the transistor. Hence it acts as a variable current source. Greater amount of IR light cause greater
The fig shows the phototransistor is wired in asimilar configuration to the voltage divider. Thevariable current traveling through the resistorcauses a voltage drop in the pull-up resistor. Thisvoltage is measured as the output of the device.
Receiver SENSOR(TSOP) MICROCONTROLLER 89S52 ULN DRIVER RELAY DC MOTOR IC REGULATORS
The TSOP 1738 is a member of IR remote control receiver series.It consists of a PIN diode and a pre amplifier which are embeddedinto a single package.The output of TSOP is active low and it gives +5V in off state.When IR waves, from a source, with a centre frequency of 38 kHzincident on it, its output goes low.Lights coming from sunlight, fluorescent lamps etc. may causedisturbance to it and result in undesirable output even when thesource is not transmitting IR signals. A band pass filter, an integrator stage and an automatic gaincontrol are used to suppress such disturbances.
TSOP module has an inbuilt control circuit for amplifying the coded pulses from the IR transmitter. A signal is generated when PIN photodiode receives the signals which is given to automatic gain control (AGC). The output of demodulator is feedback to AGC to adjust the gain to a suitable level. The signal from AGC is passed to a band pass filter to filter undesired frequencies. The filtered frequency goes to a demodulator that Drives an NPN transistor. The collector output of the transistor is obtained at pin. In this project TSOP 1738 is USED .
Microcontroller has CPU (microprocessor) RAM ROM I/O ports Timer ADC and other peripherals
CPU (microprocessor)RAMEPROM(FLASH)4 I/O ports(8 BITS EACH)Timer & Counter.Serial portWatchdog timerADC and other peripherals
The ULN2003 is a monolithic high voltage andhigh current Darlington transistor arrays.Seven Darlington per package.Output current 500mA per driver.Integrated suppression diodes for inductiveloads.Outputs can be paralleled for higher current.Inputs pinned opposite outputs to simplifylayoutInputs compatible with various types of logic.Relay driver application.
A relay is an electrically operated switch . Many relays use an electromagnet to operate a switchingmechanism.A simple electromagnetic relay, consists of a coil of wire thatsurrounds a soft iron core, known as iron yoke.A movable iron armature, and a set, or sets, of contacts.The armature is hinged to the yoke and mechanically linkedto a moving contact which is held in by a spring, so that whenthe relay is de-energized there is an air gap in the magneticcircuit. In this condition, one of the two sets of contacts in therelay pictured is closed, and the other set is open. The relayin the picture also has a wire connecting the armature to theyoke.This ensures continuity of the circuit between the movingcontacts on the armature, and the circuit track on the printedcircuit board (PCB) via the yoke, which is soldered to the PCB.
An electric motor is an electromechanical device that converts electrical energy (from a battery or voltage source) into mechanical energy (used to cause rotation).DC MOTOR: A direct current (DC) motor is a fairly simple electric motor that uses electricity and a magnetic field to produce torque, which turns the motor. At its most simple, a DC motor requires two magnets of opposite polarity and an electric coil, which acts as an electromagnet. The repellent and attractive electromagnetic forces of the magnets provide the torque that causes the DC motor to turn.
A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.____________________ The armature continues to rotate.
When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field.
The main component is IC555 .The frequency of U2 is 0.5 Hz & U1 is38 KHz which is decided by RC components connected with it. Theoutput of U2 is connected with reset pin (4) of U1.Thus U2 controlsthe operation of U1.The output of U1 is fed to two IR LEDs throughDarlington pair made up of Q1, Q2 & R5. The 9V DC battery isconnected with circuit through SPDT switch SW1 as shown below :
As shown in figure when SW1 is in position as shown the transmitter is On and also the red LED is also ON. When switch changes its position the red LED and transmitter is off and only green LED will on. When the circuit is energized U2 will start generating high pulse at every 1 sec as this pulse is fed to reset pin of U1 it will generate 38 KHz square wave and give it to IR led’s. IR led’s will generate IR beam of 38 KHz for the same time. Thus after every one second the IR beam of 38 KHz is generated for one second only.
Continue…. This cycle repeats till the red light is on, thus transmitting the IR signal which is received by the TSOP on the receiver.
As shown below 24 VAC is given to bridge rectifier & filteredthrough C1 ,then to all the regulated ICs .O/P of 7805 isconnected to 89S52 ,TSOP & also to all the LEDs. O/P of 7812(last one) is connected to common coil terminal & to ULN, theoutputs of middle four regulated ICs are connected to DCmotor through relay contacts. O/P of TSOP is connected withpin P3.3 (INT1) of mc .All five led’s are connected with portP0 .I/P of ULN is connected with Port 1 (P1.0-P1.3), & O/Pare connected with second terminal of relay coil.
WORKING OF RECEIVER Initially when you switch on the supply 89S52 will switch all the relays RL1- RL4 one by one. When any of the four relay get energized the motor will get supply from it and it will start running, motor will get 9-12-15-18 V supply in steps and gradually increases its speed reaches max speed indicated by first red LED (P0.0) and the speed remains maximum. Signal becomes red in between then IR sensor will detect IR beam & interrupts the 89S52 The interrupt given to 89S52 will switch off RL4 & switch on RL3 so, motor will get 15 V supply and its speed will be decreased. That’s indicated by second red LED (P0.1). Now 89S52 will wait for some time (2 to 3 sec) & train goes on with same speed. Red signal is now turned on ,so that 89S52 receives the interrupt & this time it will switch on Motor gets 12V supply & again its speed will be decreased indicated by third red LED (P0.2). The same procedure repeats if 89S52 is interrupted third times so the motor runs at min speed (9 V) indicated by fourth red LED (P0.3) After same delay on receiving fourth interrupt all the relays will be switched off and motor is now stop so the train is also stopped. This is indicated by green LED. Interrupts will be disabled red signal becomes green driver must reset the controller to start the train again.
Advantages: The circuit is simple and the cost is less. As it is microcontroller based the speed is automatically controlled. The circuit can be easily modified. Prevent Accidents. Fault analyze is easy.Disadvantages: Range is limited to detect the interrupt due to the use of IR sensor. The project has less accuracy.
The receiver part of the project can be modified by adding units like LCD, RF sensor, Ultrasonic sensor, Obstacle sensor, PWM. LCD: Making the use of LCD will indicate the speed of the train. RF sensor: In our project we are using IR sensor, due to which the distance at which the signal will be detected is limited and with the use of RF sensor, the distance at which the signal is detected can be increased. Obstacle sensor: Making the use of obstacle sensor in the project can detect the obstacle n the train can be stopped automatically thus avoiding accidents. PWM: Using the concept of PWM (pulse width modulation) will make the circuit simple as there will be no use of relays and the system can be made completely automatic.
ACKNOWLEDGEMENT Beginning with a very special thanks to our project guide Prof SAJID NAEEM who gave me the confidence and support to begin my Master’s degree and helped me to set my benchmark even higher and to look for solutions to problems rather than just focus on the problem. I am also very grateful to all teaching and non-teaching staff of Electronics Department for helping me to complete this task. Appreciable regards to my colleagues in chronological order of their names :Faizan, Afreen, Irfan, Keshav, Manisha, Pankaj, Prabhakar, Rimi, Shabnam, Shoaib, Abul Quais, Sufail, Swapnil, Yusuf, Ali for their moral support, co-operation and help in every possible means.
References Introduction to Embedded System (By Mohammed Ali Mazidi ) Embedded System by Raj Kamal Electronic For You (Magazine) Chip Digit (Magazine) www.embeddedgarage.com www.efy.co.in