Allen-Bradley 1756 Series, User Manual, Page: 56 / 136

56 Rockwell Automation Publication 1756-UM013B-EN-P - October 2019
Chapter 3 1756-IB16S Input Module Features
Short Circuit Protection
Short Circuit Protection helps to prevent damage to a test output that can result
when more current is present at the output than it can handle. The diagnostic is
supported on all module outputs.
Table 10 describes what happens when a short circuit
condition is detected
.
To correct the issue, remove the short.
Table 11 describes what happens when the short circuit
condition is corrected
.
For more information on the maximum current that you can apply to an output,
see the ControlLogix I/O Modules Specifications Technical Data, publication
1756-TD002 .
Test Output Recovery After Overload or Short Circuit to
Ground Condition
Table 12
describes test output recovery after overload or short circuit to ground
conditions occur.
Table 10 - Short Circuit Protection - Condition Detected
Test Output
Behavior Tag Value Diagnostic Value I/O Status Indicator
State
• Faults
• Turns off
I.Testxx.ShortCircuit tag = 1
I.Testxx.Fault tag = 1 Short Circuit diagnostic = 1 Flashing red
Table 11 - Short Circuit Protection - Condition Corrected
Test Output
Behavior Tag Value Diagnostic Value I/O Status Indicator
State
Restarts in its
commanded state. I.Testxx.ShortCircuit tag = 0
I.Testxx.Fault tag = 0 Short Circuit diagnostic = 0 Turns off if there is no
longer a load that is
connected to the
output.
Table 12 - Test Output Recovery - 1756 ControlLogix Digital Safety Input Modules
Cause of Fault Module Operating Conditions Correction Recovery Time
Overload Condition • Test Output Point Mode - Pulse Test, Power
Supply
• Test Output Data tag = 1.
• Overload current ≥ 0.7 A.
Remove the load from the test output point. After the condition is corrected, and the test
output is returned to the safe state, it recovers
in whichever of these times is higher:
• 10 seconds
• Input Error Latch Time - This time is set on
the Input Points category of the Module
Properties dialog box.
To see where to set the Input Error Latch
Time, go to
page 88 .
Short Circuit to Ground
Condition • Test Output Point Mode - Pulse Test, Power
Supply
• Test Output Data tag = 1.
• Test output is connected directly to ground.
One of the following:
• If the Point Mode for the test output is Pulse
Test or Power Supply when the Short Circuit
condition is detected, the condition can be
corrected but you cannot set the test output
to a safe state.