I recently installed a programmed system with two IB16S modules experiencing random channel faults in a 1756 rack. These modules are housed in a series C chassis and are not located near controllers or communication modules. When they fail, all connected channels display an internal fault, causing safety instructions to display code 32, indicating a loss of connection. The majority of channels show a solid red indicator, which signifies an internal fault according to the manual. Resetting the channel requires a power cycle by removing and reseating the module. Additionally, standard inputs in the rack may drop out when these faults occur. It is noted in the manual the importance of using a SELV rated power supply, and considering this system was a PLC5 backplane retrofit with a 2000s vintage linear 300W 24vdc supply powering everything in the cabinet, including modules, PLC, field inputs, and outputs, it may be the cause of the issue. Rockwell tech support suggested swapping the power supply, although a standard power cycle typically wouldn't result in multiple safety modules hard faulting. The recurring issue has happened twice in 24 hours, and further diagnostic checks will be performed if it reoccurs. All safety configurations are set to pulse, and changing to safety mode may be considered to eliminate potential interference from external factors.
What is the current method for wiring these components in the field?
In the standard procedure, each input goes through its designated test point using NC/NOHC contacts found on push/pull 800T emergency stop buttons or 440E-L lifeline pull cables.
I was referring to the wiring of the cards in connection with the power supply and any other components they come into contact with.
A single 24vdc, 12A linear power supply is connected to all devices requiring 24vdc power, including the IB16S, OBV8S, and field input devices for IB16 and OB16 modules. The rack consists of 4 IB16s, 2 OBV8S, 2 IB16S, 2 OB16, and 1 EN2TR. This setup was not my original design but was implemented by the electrical installer before I arrived to program the system. Typically, I prefer to use the AB 1606-XL power supply for similar installations, but in this particular case, I had to work with the existing setup.
It indeed sounds like quite a perplexing issue you're dealing with. The fact that standard power cycling isn't resolving the issue strongly suggests it might not be a simple electrical interference or a slight power supply issue, but something more complex. Given that the system was a retrofitted PLC5 backplane, there could be an inherent compatibility issue coming into play here. Swapping out the power supply seems worthwhile, as suggested by the Rockwell tech support. Also, it's useful to keep in mind that vintage power supplies, even though they're reliable, can sometimes introduce noise that might be causing such faults. Do check grounding and shielding techniques as well, as sometimes these tricky problems boil down to such overlooked factors. Keep us posted on the progress and good luck with the troubleshooting!
It certainly sounds like a perplexing issue, but I commend you for your thorough analysis. One possible thing to consider, as you've implicitly pointed out, is your power supply. It may not be about the power cycle, but the quality and stability of your power supply. The old 24vdc 300W could be causing noisy or uneven supply levels that these newer modules may be sensitive to. Also, check if there's a possibility of high electromagnetic interference in the cabinet or the rack's vicinity, possibly from other machines or electrical components. Even tiny amounts of such background interference can cause difficulties in signal processing. Hope this helps!
It sounds like you're dealing with a frustrating situation! Since the system is a retrofit, the older linear power supply could definitely be introducing noise or instability, especially under load. Have you considered checking the power supply voltage levels and ensuring that all connections are solid? Sometimes, grounding issues can also cause intermittent faults. Running diagnostic checks as suggested by Rockwell tech support is a good move, but it might also be worth looking into filtering solutions or a more modern power supply that adheres to the SELV guidelines to see if that stabilizes the system. Keep us posted on what you find!
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Answer: Answer: The random channel faults in the IB16S modules could be caused by an internal fault signified by a solid red indicator, which may be related to power supply considerations and safety instructions.
Answer: Answer: Resetting the channels by performing a power cycle, which involves removing and reseating the module, can help resolve the internal faults and loss of connection issues.
Answer: Answer: Using a SELV rated power supply is important as it ensures safety extra-low voltage operation and can potentially prevent issues such as internal faults in the modules.
Answer: Answer: Diagnostic checks and potentially swapping the power supply, as suggested by Rockwell tech support, are recommended steps to troubleshoot and resolve the recurring channel faults in the IB16S modules.
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