IDEC MicroSmart Pentra - Manual (Page 40)

3: I NSTALLATION AND W IRING
3-12 W EB S ERVER CPU M ODULE U SER ’ S M ANUAL FC9Y-B1278
Contact Protection Circuit for Relay and Transistor Outputs
Depending on the load, a protection circuit may be needed for the relay output of the Web server CPU modules. Choose
a protection circuit from A through D shown below according to the power supply and connect the protection circuit to
the outside of the CPU or relay output module.
For protection of the transistor output of the Web server CPU modules, connect protection circuit C shown below to the
transistor output circuit.
Protection Circuit A
Protection Circuit B
Protection Circuit C
Protection Circuit D
This protection circuit can be used when the load impedance is
smaller than the RC impedance in an AC load power circuit.
R: Resistor of approximately the same resistance value as the load
C: 0.1 to 1 µF Inductive Load Output Q
COM
C
R
This protection circuit can be used for both AC and DC load power
circuits.
R: Resistor of approximately the same resistance value as the load
C: 0.1 to 1 µF Inductive Load Output Q
COM
or
R C
– +
This protection circuit can be used for DC load power circuits.
Use a diode with the following ratings.
Reverse withstand voltage:
Power voltage of the load circuit × 10
Forward current: More than the load current
Inductive Load Output Q
COM
– +
This protection circuit can be used for both AC and DC load power
circuits. Inductive Load Output Q
COM
Varistor
or
– +