Automatic Car Park System

CASE STUDIES IN MECHATRONIC SYSTEMS:

Automatic Car Park System:

Consider the coin-operated car park system with barriers.

The main requirement of the system is that, the in-barrier is to be opened to allow the car inside if correct money (coin) is inserted in the collection box.

The out barrier is to be opened to allow the car outside, if the car is detected at the car park side of the barrier.

The automatic car park barrier along with the mechanism to lift and lower it

When the current flows through the solenoid A & the piston in the cylinder extends to move upward and causes the barrier to rotate about its pivot and thus the barrier raises to

allow the car inside.

When the current flows through the solenoid A ceases, the spring on the solenoid valve makes the contacts to open and thus makes the valve to its original position.

When the current flows through solenoid B, the piston in the cylinder moves downward end causes the barrier to get down.

Limit switches are used to detect when the barrier is down and also when fully up.

This control can be controlled by PLC

X400 –        coin operated switch at entrance to car park

X401 –        switch activated when entrance barrier is out

X402 –        switch activated when entrance barrier is down

X403 –        switch activated when car at exit barrier

X404 –        switch activated when exit barrier is -up

X405 –        switch activated when exit barrier is down

Y430 –        solenoid on valve A for entrance barrier

Y43 1         –        solenoid on valve B for entrance barrier

Y432 –        solenoid on valve A for exit barrier

Y433 –        solenoid on valve B for exit barrier

Six inputs (X400 to X405) is required for the PLC to sense the six limit switch position namely coin-operated switch, entrance barrier up switch, down switch, car at exit barrier

switch, exit barrier up switch, Exit barrier down switch

Whenever, a switch is operated, 0V signal is provided to the corresponding inputs and otherwise +24v signal is provided to the inputs. Four outputs (Y430 to Y433) are

required to operate the two solenoid valves A and B.

Program:

LD    X400

OR   Y430

ANI  M100

ANI  Y431

OUT  Y430

LD    X401

OUT T450

K      10

LD    T450

OUT M100

LD    M100

OR   Y431

ANI  X402

ANI  Y430

OUT Y431

LD    X403

OR   Y432

ANI  M101

ANI  Y433

OUT Y432

LD    X404

OUT T451

K                10

END

Assume a 10 sec delay for the car is to come inside the barrier and to go outside the barrier.

These time delays provided by T450 and T451 energising their Internal relays respectively.