Chapter 4 Installing Hardware
4-23
4.1.7.3 Transistor Output Circuit (NPN)
①
Direct-current power supply
②
Emergency stop
③
Fuse
④
Using surge absorbing diodes to extend the lifespan of contacts
1. A diode is connected in parallel to absorb the surge voltage: used in low-power situations.
VDC
+
D
ZP
Y
UP
Low power
D: 1N4001 Diode or its equivalent
2. A diode and Zener are connected in parallel to absorb the surge voltage: used in high-power and
power-on/off frequently situations.
ZD D
VDC
+
ZP
Y
UP
High power and
ON/OFF frequen tly
ZD: 9V Zener, 5W
D: 1N4001
Diode or its equivalent
⑤
Mutually exclusive output: For example, Y2 controls the clockwise rotation of the motor, and Y3
controls the counterclockwise rotation of the motor. This interlock circuit and the program in the PLC
ensure that there are protective measures if an abnormal condition occurs.
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