74
Output Surge Current
When connecting a transistor or triac Output Unit to an output device having a
high surge current (such as an incandescent lamp), care must be taken to avoid
damage to the Output Unit. The transistor and triac Output Units are capable of
withstanding a surge current of ten times the rated current. If the surge current
for a particular device exceeds this amount, use the circuit shown below to pro-
tect the Output Unit.
R
L
+
OUT
COM
PC
Another way of protecting the Output Unit lets the load draw a small current
(about one third the rated current) while the output is OFF, significantly reducing
the surge current. This circuit (shown below) not only reduces the surge current,
but also reduces the voltage across the load at the same time.
R
L
+
OUT
COM
PC
3-2-3 Electrical Noise
I/O Signal Lines
Whenever possible, place I/O signal lines and power lines in separate ducts or
tubes. If placing them together cannot be avoided, use shielded cable to mini-
mize the effects, and connect the shielded end to the GR terminal.
Suspended duct
In-floor duct
Conduits
1 = I/O cables
2 = Power cables
Wiring
Section 3-2
