Chapter 5 Device
5-13
5.2.5 Output Relays (Y)
Output function
The output sends the ON/OFF signal to drive the load connected to the output, such as an external signal
lamp, a digital display, or an electromagnetic valve. There are four types of outputs: relays, transistors (NPN
and PNP), and TRIACs (thyristors). You can use the output contact A or contact B several times in the
program. Use output Y only once in the program; otherwise, according the PLC’s program-scanning
principle, the state of the output depends on the circuit connected to the last output Y in the program.
Output number (the decimal number)
For the PLC, the output numbers start from Y0.0. The number of outputs varies with the number of outputs
on the digital input/output modules. The outputs are numbered according to the order in which the digital
input/output modules are connected to the PLC. The maximum number of outputs on the PLC is 1024, and
the range is between Y0.0 and Y63.15.
An output that is not used as an output device can be used as a general device.
Output types
Outputs are classified into two types.
1. Regenerated output: The state of a regenerated output is not written until the program executes the
instruction END according to the states of the outputs. For example, OUT Y0.0.
2. Direct output: The state of a direct output is written by the PLC during the execution of the instructions
according to the states of the outputs. For example, OUT DY0.0.
5.2.6 Auxiliary Relays (M)
The auxiliary relay has contact A and contact B. It can be used several times in the program. You can combine
the control loops with the auxiliary relay, but you cannot drive the external load with the auxiliary relay. You can
use the auxiliary relays in either of two ways.
1. For general use: In general use, if an electrical power interruption occurs when the PLC is running,
the auxiliary relay is reset to OFF. When the power is restored, the auxiliary relay
remains OFF.
2. For latched use: In latched use, if an electrical power interruption occurs when the PLC is running,
the state of the auxiliary relay states for latched use is retained. When the power
supply is restored, the state remains the same as before the power interruption.
5.2.7 Special Auxiliary Relays (SM)
Every special auxiliary relay has its own specific function. Refer to section 2.2.7 in the AS Series Programming
Manual for more information.
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