Introduction to Industrial Automation

Figure 7.74  Program in LAD language for operation of the drilling machine shown in Figure 7.73.

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346

 

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  Introduction to Industrial Automation

PLC

Input

s

Output

s

Q3.0

Q4.0

Q4.

1

I11.0

I10.0

F

1

–F

10

SL

Coin box

Coin return

slot

F

12

A

F

13

F

14

F

15

B

C

Μ

b

F

11

Slot machine

0 V

+24 V DC

0 V

+24 V DC

I1.

0

Q1.0

Q2.0

Μ

righ

t

I12.0

I13.0

h

G

SL

F

1

b

I14.0

I15.0

I20.0 

h

R

Μ

left

F

10

F

11

F

12

F

13

F

14

F

15

ΑC

CA

Fi

gu

re 7

.7

5 

Th

e e

le

ct

ro

m

ec

ha

ni

ca

l b

ow

lin

g e

qu

ip

m

en

t (

in s

im

pl

ifi

ed f

or

m

) i

s c

on

tr

ol

le

d b

y a P

LC

.

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Basic Programming Principles of PLCs 

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347

ball twice in his effort to knock down all the bowling pins. If during the first try the player 

knocks down all the pins, the attempt ends. If after the first try, there are any pins still stand-

ing, the player has a second chance to knock down the remainder of the pins. The operating 

specifications are as follows:

  1. Bowling works with a coin slot mechanism. In order for the coin box to accept a coin, three 

preconditions should exist: [to press the button b] AND, [the 10 pins to be in their place] 

AND, [the pin bracket is in position B]. This situation is noted as a normal resting state.

  2. To drive the coin into the coin box (according to 1), the solenoid (SL) should be activated. 

When the SL is not activated, the coin that the player is putting in the box comes out in the 

coin return slot.

  3. As soon as the coin passes in front of the sensor F

11

, the solenoid SL is deactivated because 

the slot does not accept coins during the game and returns them to the player. The mecha-

nism of the pin bracket comes in position A, allowing the player to roll the ball. The light 

indicator h

R

 is turned on, which means that the game is in progress, i.e., the player has not 

completed the 12 double attempts. Simultaneously, the light indicator h

G

 turns off (see 

specification 7).

  4.  All the pins are detected by a corresponding proximity switch (F

1

-F

10

). After the first attempt, 

the number of knocked down pins is stored, and if all of them were not knocked over, the 

system expects the second attempt of the player. If all the pins were knocked over, the actions 

listed below after the second attempt should follow. After the second attempt and after the 

ball passes in front of the F

12

 sensor, the number of knocked down pins is also stored. The 

mechanism (M) rotates the pin bracket from point A to point C, pushing the upright or 

fallen pins towards the mechanism for their repositioning (how this mechanism operates 

is not included in this current automation study). After a time delay of 3 s, the pin bracket 

(M) returns to point A, and at the same time, 10 pins are repositioned by the corresponding 

mechanism.

  5. The score of each player’s attempt consists of the total number of pins that were knocked 

down in both attempts, which are stored in the PLC.

  6. The player’s overall score is the sum of his individual scores over 12 double attempts, which 

also has to be recorded in the PLC.

  7. When 12 double attempts have been made, the system should return to its initial resting 

state, that is, the mechanism (M) rotates the pin bracket from point A to where it blocks 

point B, hence the continuation of the game until the next coin insertion in the coin slot 

machine. The h

G

 indicator lights up, thus indicating that the game is over and that the bowl-

ing system can accept a new coin, which deactivates the h

R

 indication at the same time.

The most difficult issue in this project, from the programming point of view, will be the count-

ing of the knocked down pins by a single counter, under the real assumption that it is impossible 

for all the pins to be knocked over at different scan-cycles of the PLC.