plc timers - 9.32

9.10 PRACTICE PROBLEM SOLUTIONS

1.edge triggered means the event when a logic signal goes from false to true (positive edge) or from true to false (negative edge).

2.no, but they are essential for retentive timers, and very important for counters.

3.these are limited by the 16 bit number for a range of -32768 to +32767

4.the un underflow bit. This may result in a fault in some PLCs.

5.

first pass

U motor

stop

start

L motor

start

stop

motor

motor

6.

input
TON	delays turning on
TOF	delays turning off

plc timers - 9.33

7.

				RTF
	A			Timer T4:0		(DN)
				Time Base 0.01
				Preset 350		(EN)
				Accum. 0

A
T4:0/EN
T4:0/DN
T4:0/TT
T4:0.Accum.
0	3	6	10	16	18	20

plc timers - 9.34

8.

				RTO	(DN)
	A			Timer T4:0
				Time Base 1.0
					(EN)
				Preset 10
				Accum. 1

A
T4:0 EN
T4:0 TT
T4:0 DN
T4:0 Accum.
0	3	6	9	14	17	19	20
			TOF

	A			Timer T4:1		(EN)
				Time Base .01
				Preset 50		(DN)
				Accum. 0

A

T4:1 EN

T4:1 TT

T4:1 DN

T4:1 Accum.

0

15

45

150

200

225

plc timers - 9.35

9.

input

TON

RTO

TOF

RTF

sec

0

1

2

3

4

5

6

7

10.

A			RTO
			Timer T4:0
			Base 1.0
			Preset 2
A
			RES T4:0

11.

	A		T4:0/DN			TON
						Timer T4:0
						Base 1.0
						Preset 3600
T4:0/DN
						CTU
						Counter C5:0
						Preset 1200

C5:0/DN

Light

plc timers - 9.36

12.

I/1

B3/0

B3/0

T4:0/DN

13.

I/2

I/1

C5:0/DN

B3/0

TON

T4:0

delay 15 sec

O/01

C5:0 RES

CTU

C5:0 presetR 10

O/1

plc timers - 9.37

14.

	I/1				T4:1/DN

T4:0/DN

T4:0/DN

T4:1/DN

C5:0/DN

TON

T4:0 delay 20 s

TON

T4:1 delay 20 s

O/1

L

CTU

C5:0 preset 3

O/1

U

plc timers - 9.38

15.

go

stop

C5:0/DN

C5:1/DN

motor

motor

go

CTU

Counter C5:0

Preset 2

Accumulator 1

CTU

Counter C5:1

Preset 3

Accumulator 1

C5:1/DN

RES

C5:0

RES

C5:1

stop

C5:0/DN

CTD

Counter C5:0

Preset 2

Accumulator 1

CTD

Counter C5:1

Preset 3

Accumulator 1

plc timers - 9.39

16.

	left button			TON
				Timer T4:0
				Base 0.01
				Preset 25
	right button			TON
				Timer T4:1
				Base 0.01
				Preset 25

	T4:0/TT			T4:1/TT			stop
										on
	on

plc timers - 9.40

17.

S1

CTU

Counter C5:0

Preset 6

CTU

Counter C5:1

Preset 1

S2

CTD

Counter C5:0

Preset 6

CTD

Counter C5:1

Preset 1

C5:0/DN

C1

C5:1/DN

C2

C5:0/DN

TON

Timer T4:0

Preset 30s

T4:0/DN

RES C5:0

RES C5:1

plc timers - 9.41

18.

	A	C5:0/DN
			TON
			timer T4:0
	T4:0/TT		delay 5s
		T4:0/TT	T4:2/DN
			TON
			timer T4:1
			delay 0.25s
		T4:1/DN	TON
			timer T4:2
			delay 0.75s
			CTU
			counter C5:0
			preset 5
	T4:1/TT		light
	B		RES

plc timers - 9.42

19.

First scan

TON

T4:0

delay 15s

T4:0/TT

T4:2/DN

TON T4:1 delay 0.5s

T4:1/DN

TON

T4:2 delay 0.5s

T4:2/TT	light

20.

		start		stop
								active
		active
		enter
							CTU
							counter C5:0
							preset 10
		exit
							CTD
							counter C5:0
							preset 10
		active		C5:0/DN
								active

21. The normal output ‘Y’ is repeated twice. In this example the value of ‘Y’ would always match ‘B’, and the earlier rung with ‘A’ would have no effect on ‘Y’.