3. External Connection
40
SMC-4DL-PCI, SMC-8DL-PCI
Surge Voltage Countermeasures
When connecting a load that generates surge voltages and inrush currents, such as an induction load
(relay coil) or an incandescent light bulb, to the digital output, appropriate protection must be provided
in order to prevent damage to the output stage or a malfunction due to noise. The rapid shutoff of a coil,
such as a relay, generates a sudden high-voltage pulse. If this voltage exceeds the voltage tolerance level
of the output transistor, it can cause the transistor to gradually deteriorate, or even completely damage
the transistor. Therefore, when driving an induction load, such as a relay coil, you should always
connect a surge-absorbing device. The following illustrates a surge voltage countermeasure that can be
employed:
Examples of use of relay coil
Examples of use of lump
Diode
Relay
coil
Surge current
prevention
resistor
GND
OUT 1 - 3
External
Power Supply
+12 - +24VDC
GND
OUT 1 - 3
External
Power Supply
+12 - +24VDC
Board
Board
External power voltage < Zener diode voltage
Resistor
Zener
diode
Relay
coil
External
Power Supply
+12 - +24VDC
External
Power Supply
+12 - +24VDC
GND
OUT 1 - 3
GND
OUT 1 - 3
Board
Board
Figure 3.15. Surge Voltage Countermeasure
CAUTION
In order for a protection circuit to operate effectively, it must be connected within 50 cm of a load
and a contact point.
Содержание SMC-4DL-PCI
Страница 7: ...vi SMC 4DL PCI SMC 8DL PCI ...
Страница 30: ...2 Setup SMC 4DL PCI SMC 8DL PCI 23 3 Simple operation is performed ...
Страница 55: ...4 Functions 48 SMC 4DL PCI SMC 8DL PCI ...
Страница 59: ...5 About Software 52 SMC 4DL PCI SMC 8DL PCI ...