February 2012 11 – 123
Checking the
PLC outputs
8 You have called the TABLE.
8 Press the OUTPUT soft key.
8 Place the cursor on the output to be examined (e.g. GOTO O2 ENTER).
8 Observe the logical state of the output to be checked.
8 Check whether the connected actuator (relay, etc.) has triggered or whether the connected
device operates.
8 Measure the 24-V supply voltage for the PLC.
8 Measure the voltage for the output to be checked, e.g.:
At the terminal strips in the electrical cabinet where the PLC outputs are connected.
Directly at relay terminals, etc.
At the terminals (X7) of the MB 620 machine operating panel.
At the terminals (X6) of the UEC 11x compact controller unit.
At the terminals (X9) of the PLB 62xx system module.
At the terminals (X21, X22) of the I/O module PLD-H 16-08-00 or PLD-H 08-16-00.
Assignment --> See ”Connector designations and pin layouts” on page 28 – 453.
Conclusion The logic states in the PLC table must be in agreement with the voltage levels for each output.
--> See ”Specifications” on page 11 – 144.
Meaning of the
LEDs on the
I/O module PLD-H
The output voltage for the "1" signal must not be more than 3 V below the measured
24-V supply voltage (e.g., 22.7 V - 3 V = 19.7 V).
An active output is signaled by a yellow LED at the PLD-H.
It is not possible to measure PLC outputs directly at the handwheel or at the cable adapter for the
handwheel!
LED Status Meaning
Red LED at X11, pin 1 Blinking I/O module OK
Permanently on or off I/O module faulty
Yellow LEDs at X11, X12 and X21 On Inputs/outputs set
Green LEDs at X21, pin 9 and pin 10 On 24-V power supply of the outputs
In order to recognize a short circuit, a current of least 20 A must be able to flow for approximately
3 ms. If this is not the case (e.g. the 24-V supply limits the current sooner), the short-circuit
monitoring might not become effective.
If an output is short-circuited the output voltage is reset. Short-circuit monitoring remains active.
It can be reset with the PLC program of the machine manufacturer or by switching the machine
off and on.
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