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Programming Tips for Timers and Counters
4.6.4
Clock signal generators
The controllers have special relays that make it very easy to program tasks requiring a regular
clock signal (for example for controlling a blinking error indicator light). Relay M8013 switches
on and off at 1-second intervals, for example. For full details on all special relays see the Pro-
gramming Manual for the FX family.
If you need a different clock frequency or different on and off times you can program your own
clock signal generator with two timers, like this:
Ladder Diagram
X001
0
T1
5
Input X1 starts the clock generator. If you want, you can omit this input – then the clock genera-
tor is always on. In the program you could use the output of T1 to control a blinking warning
light. The on period is determined by T2, the off period by T1.
The output of timer T2 is only switched on for a single program cycle. This time is shown much
longer than it really is in the signal sequence illustration below. T2 switches T1 off and immedi-
ately after this T2 itself is also switched off. In effect this means that the duration of the on
period is increased by the time that it takes to execute a program cycle. However, since the
cycle is only a few milliseconds long it can usually be ignored.
Signal sequence
ON
X0
OFF
1
T1
0
1
T2
0
ON
Y1
OFF
4 – 20
K10
T2
T1
K20
T2
Y000
t1
t2
Devices in Detail
Instruction List
0
LD
X001
1
ANI
T2
2
OUT
T1
5
LD
T1
6
OUT
T2
9
OUT
Y000
t
MITSUBISHI ELECTRIC
K10
K20
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