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AUTOMATIC

LIFT CONTROL SYSTEM

 

INTRODUCTION

AUTOMATIC LIFT CONTROL is our major project. This project can be used at the various places like our apartments, malls, buildings etc.

In this project we use one dc motor  for the lift. Few reed sensor to monitor the lift In this lift when we start the lift then we use start switch. After pressing a start switch stepper motor start and when it reaches to the first floor then firstly we sense the floor by reed sensor. Reed sensor is magnetic sensor, when  magnet connected to the lift is  near by the reed sensor then reed sensor is activate and provide a signal to the controller.

In this case we will use switches to send the signal through optocouplers and  8052 controller. Optocouplers are used to isolate the circuit. This is the protection circuit which used to protect the 8052 controller.

Then the 8052 controller is used to drive the dc motor through current amplification circuit. The step motor rotates and the lift is shifted to first floor and then second and so on.

For the ground floor we use reed sensors which are attached to the 8052 controller.

The position of the lift or floor number is displayed on the LCD. We use 16*2 lcd for showing the output.. 

 

 

 

                                                                                              

HARDWARE DESCRIPTION

 

 

MOTORS

To make the robots mobile we need to have motors and the control circuitry that could control the motors. There are different kinds of motors available for different application.

1.     DC motor

2.     Stepper motor

3.     Servo motor

DC motors

          These are the motors that are commonly found in the toys and the tape recorders. These motors change the direction of rotation by changing the polarity. Most chips can't pass enough current or voltage to spin a motor. Also, motors tend to be electrically noisy (spikes) and can slam power back into the control lines when the motor direction or speed is changed.

Specialized circuits (motor drivers) have been developed to supply motors with power and to isolate the other ICs from electrical problems. These circuits can be designed such that they can be completely separate boards, reusable from project to project.

A very popular circuit for driving DC motors (ordinary or gearhead) is called an H-bridge. It's called that because it looks like the capital letter 'H' on classic schematics. The great ability of an H-bridge circuit is that the motor can be driven forward or backward at any speed, optionally using a completely independent power source. This circuit known as the H-bridge (named for its topological similarity to the letter "H") is commonly used to drive motors. In this circuit two of four transistors are selectively enabled to control current flow through a motor. opposite pair of transistors (Transistor One and Transistor Three) is enabled, allowing current to flow through the motor. The other pair is disabled, and can be thought of as out of the circuit.

By determining which pair of transistors is enabled, current can be made to flow in either of the two directions through the motor. Because permanent-magnet motors reverse their direction of turn when the current flow is reversed, this circuit allows bidirectional control of the motor.

It should be clear that one would never want to enable Transistors One and Two or Transistors Three and Four simultaneously. This would cause current to flow from Power + to Power - through the transistors, and not the motors, at the maximum current-handling capacity of either the power supply or the transistors. This usually results in failure of the H-Bridge. To prevent the possibility of this failure, enable circuitry as depicted in Figure is typically used.

In this circuit, the internal inverters ensure that the vertical pairs of transistors are never enabled simultaneously. The Enable  input determines whether or not the whole circuit is operational. If this input is false, then none of the transistors are enabled, and the motor is free to coast to a stop.

By turning on the Enable input and controlling the two Direction inputs, the motor can be made to turn in either direction.

Note that if both direction inputs are the same state (either true or false) and the circuit is enabled, both terminals will be brought to the same voltage (Power + or Power - , respectively). This operation will actively brake the motor, due to a property of motors known as back emf, in which a motor that is turning generates a voltage counter to its rotation. When both terminals of the motor are brought to the same electrical potential, the back emf causes resistance to the motor's rotation.

Stepper motors

          Stepper motors are special kind of heavy duty motors having 2 or 4 coils. The motors will be stepping each time when it get the pulse.  As there are many coils in the motors we need to energize the coils in a specific sequence for the rotation of the motor. These motors are mostly used in heavy machines. The figure shown below consists of a 4 coil stepper motor and the arrow mark will rotate when the coils are energized in the sequence.

 

          Unlike DC motors stepper motors can be turned accurately for the given degrees.

 

Servo motors

          Servo motors unlike the stepper motor it has to be controlled by the timing signal. This motor has only one coil. It is mostly used in robots for its lightweight and low power consumption. The servo motors can also be accurately rotated by the making the control signal of the servo motor high for a specific time period. Actually the servo motor will be having 3 wires where 2 are for power supply and another one is for the control signal.

 

LCD

 

LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of applications. A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments), animations and so on.

 

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command and Data.

 

 

 

Pin Description: 

 

 

 Pin No

 Function

 Name

1

Ground (0V)

Ground

2

Supply voltage; 5V (4.7V 5.3V)

 Vcc

3

Contrast adjustment; through a variable resistor

 

 VEE

4

Selects command register when low; and data register when high

Register Select

5

Low to write to the register; High to read from the register

Read/write

6

Sends data to data pins when a high to low pulse is given

Enable

7

8-bit data pins

DB0

8

DB1

9

DB2

10

DB3

11

DB4

12

DB5

13

DB6

14

DB7

15

Backlight VCC (5V)

Led+

16

Backlight Ground (0V)

Led-

 

 

 

 

 

 

Components required:

 

8052 MICROCONTROLLER

Crystal 11.592 MHz- 1 nos.

On/off Switch- 1 nos.

Diodes IN 4001- 10 nos.

Optocoupler 817- 2nos.

Cap 10f,0.1 f,330f

Transistors -547or 548

Resistances 330 Ω,8.2kΩ,30pf

LED

IC7805  voltage Regulator

Motors stepper

Infrared sensors set

Copper Clad board

Ply board

Ferric Chloride

Wires

Soldering iron

Soldering wire

Flux

 

 

 

 

 

 

 

 

HARDWARE REQUIRED

pic programmer universal kit

CRO 20 Mhz

Digital multimeter

 

 

SOFTWARE REQUIRED

 

 

OrCAD for PCB designing

 

Proteus 7.6 Simulation

 

 

 

BIBLIOGRAPHY

 

 

http://www.kmitl.ac.th/~kswichit%20/#8051

 

http://www.bobblick.com/techref/projects/hbridge/hbridge.html

 

http://www.solarbotics.net/starting/200111_steppermotor/200111_steppermotor2.html

 

http://www.atmel.com/atmel/acrobat/doc1919.pdf