5-35
5 Installation
CJ2 CPU Unit Hardware User’s Manual
5-3 Wiring
5
5-3-5 Connecting I/O Devices
z Output Short-circuit Protection
If a load connected to the output terminals is short-circuited, output components and the printed cir-
cuit boards may be damaged. To guard against this, incorporate a fuse in the external circuit. Use a
fuse with a capacity of about twice the rated output.
z Transistor Output Residual Voltage
A TTL circuit cannot be connected directly to a transistor output because of the transistor's residual
voltage. It is necessary to connect a pull-up resistor and a CMOS IC between the two.
z Output Surge Current
When connecting a transistor or triac output to an output device having a high surge current (such
as an incandescent lamp), steps must be taken to avoid damage to the transistor or triac. Use either
of the following methods to reduce the surge current.
Output Wiring Precautions
OUT
R
COM
L
+
OUT
R
COM
L
+
Method 1
CS/CJ-series
PLC
CS/CJ-series
PLC
Add a resistor that draws about 1/3 of the current consumed by the bulb.
Method 2
Add a control resistor as shown in the following diagram.
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