User`s manual

Selecting I/O modules Input and output modules
MELSEC System Q, Hardware 6 – 1
6 Input and output modules
6.1 Selecting I/O modules
Triac outputs
It is recommended to use triac output modules instead of relay output modules if:
● The outputs should be switched in fast sequence on and off
● A load with high inductance or low power factor should be switched
When using relays for these applications, the life of relay contacts is reduced considerably.
On and off times when switching inductive loads
The on and off time for switching an inductive loads must be minimum 1 s.
Inrush current
When controlling external counters or time switches with DC/DC converters, problems can
occur at the output module by periodical current peaks, when only the mean value of the current
was taken into consideration for selecting the module.
A resistor or an inductance in series to the load can reduce current peaks. Alternatively select
an output module for switching higher load currents.
Input response time
The response time of input modules can be set by parameters. Increase the response time for
example to disable short noise pulses, which be recognised with short response time as a set
input.
On the other hand "real" input pulses may not be recognised, if the response time is set too long.
The following table shows the response time and the corresponding minimum recognisable
pulse width.
Response time setting [ms] Minimum value of pulse width that may be imported [ms]
10.3
53
10 6
20 12
70 45
Tab. 6-1: Recognisable pulses