I am currently utilizing the Schneider-Electric encoder module BMXEAE0300 in conjunction with the BMXP342020 Processor for a crane application. The encoder being used is an absolute type EPM 50S8-1013-B-S-24 from Autonics, mounted at the motor's shaft end. While the crane is in operation, there is a sudden and abrupt increase in the encoder value within the PLC, causing the crane to continue moving beyond its intended stopping point. Despite the error resetting, the new value surpasses the desired count, leading to operational disruptions. Despite efforts to mitigate electromagnetic interference by routing the cable separately, the issue persists. Are there any recommendations or solutions to address this recurring problem?
The encoder on your device appears to have a range of 0 to 8191. Any sudden fluctuations in the signal from an absolute encoder may be attributed to interference, resembling noise. When you mention a 'screen cable,' are you referring to a shielded encoder cable? It is recommended to use a 2 pair separately shielded cable or a 2 pair cable with an overall shield for better signal integrity. Although I am not well-versed in the electrical interface of SSI, which is apparently how your encoder communicates with the PLC, Wikipedia suggests it is based on RS422, known for its high tolerance to noise with just a 2 pair instrument cable. Make sure the cable shield is grounded only at the processor end to prevent any interference. As for the resets you mentioned, are you indicating that the encoder value suddenly decreases on its own or that there are errors in the PLC channel? Unfortunately, I do not have any other suggestions at the moment. Good luck with resolving the issue!
It sounds like you've already tried some common solutions, so I'm going to suggest something a bit different. It's possible that mechanical vibration or shock is causing your encoder to send errant signals to your PLC. You mentioned the encoder is at the motor's shaft end - is it adequately insulated against vibration? If not, the frequent starts and stops of a crane application could cause it to misread. It might be worth examining your mounting arrangement and checking it against the manufacturer's recommended setup. Similarly, you may also want to inspect if the signal transmission path is too long or is improperly shielded which may result in noise interfering with the correct reading. Remember also that software error detection and correction routines can solve some of these issues.
From what you've described, it sounds like the problem might not be coming from electromagnetic interference. One possibility could be that your encoder and PLC's specifications aren't matching properly. In my experience, such abrupt increases in encoder values are often caused by incorrect configuration or mismatched hardware. Please ensure the settings in your PLC match the encoder input specifications. This pertains especially to the number of pulses per revolution and resolution. The other issue could be mechanical in origin - perhaps some misalignment or issues with coupling. Lastly, consider upgrades to your software or firmware. It's advisable to contact Schneider Electric or Autonics directly regarding this issue for a more comprehensive diagnostic.
It sounds like you've already tackled the most common cause of unexpected encoder behavior, which is interference from electromagnetic sources. Another possibility could be a problem with the encoder itself. I would suggest, if possible, to replace the current encoder with another unit to see if the problem persists. Alternatively, the sudden jump in the encoder value could be an artifact from the code in transformer circuit of your PLC. Check to see if any abrupt data changes could be causing the error. Finally, ensure that homing procedures upon startup are optimized, too. Sometimes simple recalibrations, reorientations, and resetting software or firmware updates can offer solutions when hardware seems to be functioning properly.
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Answer: - The abrupt increase in encoder value may be due to electromagnetic interference or other external factors affecting the encoder module's performance.
Answer: - To troubleshoot encoder value spikes, you can check the cable routing, grounding, and shielding to minimize electromagnetic interference. Additionally, inspect the encoder module and its connections for any faults.
Answer: - Solutions may include improving cable routing, using shielded cables, adding filtering components, ensuring proper grounding, and potentially considering a different encoder module or configuration.
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