Chapter 4 Installing Hardware and Wiring
4-65
4.8.2.3 Transistor Output Circuit
The AH500 series transistor outputs are equipped with the diodes which provide the counter-electromotive
force protection. They can be used if they are not turned ON/OFF frequently and there are low-power
inductive loads. If they are turned ON/OFF frequently and there are high-power inductive loads, they must be
connected to noise suppression circuits to reduce the noise and prevent the overvoltage or the overheating
from damaging the transistor output circuit.
NPN/PNP transistor output circuit
Direct-current power supply
④
The output terminals of a transistor module are open-collector output terminals. If Y0.0/Y0.1 is a pulse
train output terminal of a transistor module, the output current passing through its output pull-up
resistor must be greater than 0.1 A to ensure that the transistor module operates normally.
A relay or a solenoid valve is used as a DC load. A diode is connected in parallel to absorb the surge
voltage which occurs when the load is OFF.
DC power supply
ZP
Y0.0
UP
+
D
Relay/Solenoid valve
NPN transistor output (sinking)
D: 1N4001 diode
ZP
Y0.0
UP
+
D
PNP transistor output (sourcing)
D: 1N4001 diode
DC power supply
Relay/Solen oid valve
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