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A project on the control of an elevator

using PLC

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To design and simulate the working of an elevator

servicing a four story building

To develop logic for the operation of the elevator To simulate the working of the logic in a suitable

programming software like C++

To implement the hardware for the level translation of

PLC to interfacing card voltage and vice versa

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Process

Elevator starts off at the ground floor

Calls from various floors are taken in as input

Calls answered as elevator moves up Elevator reaches top floor

Calls answered as elevator moves down

Elevator reaches ground floor

Process repeats

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Process Chart

Calls

Groundfloor

UP callsanswered

Top floor

DOWNcalls

answered

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Modules UP cycle

DOWN cycle

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PC Implementation Choice of C++ based on following factors

Simplicity and familiarity

Modular function based approach

Number comparison functions

Ease in duplicating and assigning variables

Timer functions

Counting functions

Logic can be scaled to PLC level

Relatively easy debugging

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The Code Modules

Function based

Four user defined functions One main function

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Modular Approach Main() function

Check_call_up()

Check_call_down() Up_cycle()

Down_cycle()

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Logic and Code Header files added are as follows

#include

#include

#include #include

Global Variables defined are as follows int cur_pos = 0;

int calls[4];

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Check_call_up() Checks for up calls

void check_call_up()

{

int t;

for (int i=cur_pos;i

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Check_call_down() Similar to check_call_up()

void check_call_down()

{

int t;

for (int i=cur_pos;i>1;i--)

if (calls[i]==0)

{

cout

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Up_cycle() Status display messages

Movement of elevator

Check for call Door status message

Check for new calls

Repeat cycle

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Level Translator Circuit Elevator interface consists of ICs of 3.5 to 5V high and

0 to 2.5V low

PLCs work at a voltage level of 24V high and 0V low Step down part mainly consists ofoptocoupler ICs

Step up part is a TTL circuit

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Applications of elevator Transport of people from floor to floor. Eliminates the

need for stairs or escalators.

Carrying loads. Can be used as a scaled down and inexpensive version

of a crane or lift. Control via remote location for liftingof heavy goods.

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Thank You