Troubleshooting - DirectLOGIC DL405 Manual

Troubleshooting

If the D4–INT interrupt input module does not seem to be working properly, check the
following items.
The following table provides additional troubleshooting details:
Symptoms
TB indicator is ON
Input indicator lights do not come on. 1. Power not present.
CPU does not initiate actions in sub-
routine quickly enough.
Interrupt does not occur.
1. Wiring connections: Incorrect and loose wiring cause the majority of
problems. Verify you have wired everything correctly and that the
connections are tight.
2. DIP switch settings: Make sure you have set all the DIP switches
correctly. (Page 10 shows the various settings available.)
3. Noise or bounce: If the field device you have connected has too much
contact bounce, or if you are possibly picking up some noise on the input,
try additional input filtering by setting the DIP switches to the Slow
Response Delay. This is available on X0–X3 only. Refer to Page 10 for the
proper DIP switch settings.
Possible Causes
Terminal block is loose.
2. Invalid DC level signal
being sent to module.
1. Immediate instructions have
not been used in subroutine.
2. Critical action logic too far
down in scan of subroutine.
1. ENI and DISI instructions
are not entered properly.
2. Input signal does not last
longer than the shortest
selected Response Delay
time.
3. Bad module.
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Corrective Action
Make sure terminal block is
securely connected to the
module.
1. Apply power.
2. Check the voltage level of
the incoming signal.
1. Use immediate instructions
where possible.
2. If possible, make
critical actions are placed on
rungs immediately following
the INT box.
1. Check these commands in
the main program.
2. Find a way to make the
input pulse last longer.
3. Replace the module.
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sure