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page 306

22.4 DESIGN CASES

22.4.1 Counters And Timers

Part A - Develop the ladder logic that will turn on an output light, 15 seconds after switch A has been turned on.

Part B - Develop the ladder logic that will turn on a light, after switch A has been closed 10 times. Push button B will reset the counters.

 

 

 

 

 

 

 

A

 

 

TON

T4:0

 

 

 

 

 

 

Time base: 1.0

 

 

 

 

 

 

 

 

Preset 15

 

 

 

 

 

 

T4:0/DN

Light

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A

 

 

CTU

C5:0

 

 

 

 

Preset 10

 

 

 

 

 

 

 

 

Accum. 0

 

 

 

 

C5:0/DN

Light

 

 

 

 

 

 

 

 

 

 

B

C5:0 RES

22.4.2 More Timers And Counters

Develop a program that will latch on an output ‘B’ 20 seconds after input A has been turned on. After ‘A’ is pushed, there will be a 10 second delay until ‘A’ can have any effect again. After

page 307

‘A’ has been pushed 3 times, ‘B’ will be turned off.

A

On L

On

TON

T4:0

 

 

 

 

 

Time base: 1.0

 

 

 

 

Preset 20

 

 

 

 

 

T4:0/DN

Light

L

 

 

 

 

 

 

 

 

 

 

 

 

 

 

T4:0/DN

TON

T4:1

 

 

 

 

 

Time base: 1.0

 

 

 

 

Preset 10

 

 

 

 

 

T4:1/DN

On

U

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

On

CTU

C5:0

 

 

 

 

 

Preset 3

 

 

 

 

 

 

Accum. 0

 

 

 

 

 

C5:0/DN

Light

U

 

 

 

 

 

 

 

 

 

 

 

22.4.3 Oscillator

• An oscillator will be designed that will turn on for 1 seconds and off for 1.5 seconds continuously.

page 308

22.4.4 More Timers

• Design ladder logic that allows an RTO to behave like a TON.

22.4.5 Cascaded Timers

• Design ladder logic that uses normal timers to measure times of 5.0 days.

22.4.6 Deadman Switch

A motor will be controlled by two switches. The Go switch will start the motor and the Stop switch will stop it. If the Stop switch was used to stop the motor, the Go switch must be thrown twice to start the motor. When the motor is active a light should be turned on. The Stop switch will be wired as normally closed.

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Motor

Stop

C5:0

RES

Go

 

Motor

CTU

C5:0

 

 

 

 

 

Preset 2

 

 

 

 

 

 

 

 

 

 

 

 

Accum. 1

 

 

 

 

 

 

 

C5:0/DN

Stop

Motor

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Motor

Light

Consider:

- what will happen if stop is pushed and the motor is not running?

22.4.7 Conveyor

A conveyor is run by switching on or off a motor. We are positioning parts on the conveyor with an optical detector. When the optical sensor goes on, we want to wait 1.5 seconds, and then stop the conveyor. After a delay of 2 seconds the conveyor will start again. We need to use a start and stop button - a light should be on when the system is active.

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