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Alarms
PLC300 | 10-1
10 ALARMS
The alarms are an important tool in process automation, allowing the user to monitor its
plant, checking critical points and signaling to the operator. In the PLC300, the alarms can
be programmed by the user, being activated by a bit marker that can be set on the ladder.
For instance, when an analog input exceeds a certain value, indicating an abnormal
condition or when a digital input is activated by some sensor.
Some result of a mathematical operation, a counter that exceeds a value, etc.
When an alarm occurs, the red LED of the <ALARM> key flashes indicating that there is
a new active alarm.
The internal alarms are not programmable and inform unwanted conditions in the equipment
hardware. They can be disabled by the user, except for the low battery alarm.
10.1 INTERNAL ALARMS
They are alarms related to some hardware components of the PLC300. They are not
programmed by the user. They have fixed texts.
They occupy the internal memory, not the user memory, except by the history.
They can generally be disabled by the WPS, except for the ‘Low Battery’ alarm, which
informs that the battery that keeps the data in the memory must be changed.
Enabling and disabling the internal alarms is also executed by the WPS.
Description of the internal alarms:
Digital Outputs Fault
– indicates that some problem is occurring in some of the outputs
DO1 to DO8, DO101 to D0108 or DO201 to DO208. It can be overheating caused by a
short circuit, or overload in the outputs.
Broken Wire – when the analog input is in current mode, 4 to 20 mA and the current is
below approximately 2 mA, the alarm goes off. The normalization of this alarm happens
when the current increases to above the 3 mA again.
Encoder Fault – if any of the encoder signals is missing, this alarm is activated. After the
normalization of the fault, the system must be reset.
Can Supply
– the CAN Interface needs a voltage between 11 and 30 Vdc for its correct
operation. In the absence of this voltage, this alarm is activated.
Low Battery – indicates that the battery that keeps the data in the memory must be
changed. This alarm cannot be disabled by the user. This alarm is generated when the
battery voltage is below 2.0 V, and it is deactivated when the voltage is above 2.5 V.