Greetings everyone! Currently, we are in the process of determining the downtime percentage on our machines. However, this calculation is only accurate when the PLC has a constant power supply. The issue arises during our routine 5 to 10-hour preventive maintenance sessions, where we need to factor in the time without power into our downtime percentage calculation. I am considering a method involving calculating the PLC_Counted_Minutes_Since_Shiftchange (triggered by a specific condition) and subtracting this from the Actual_Minutes_Since_Shiftchange (yet to be determined) in order to incorporate this into our downtime analysis. Does this approach seem feasible, or is there a more effective strategy to address this issue? I am struggling to devise a logical solution to calculate the Actual_Minutes_Since_Shiftchange following a powerup. Any guidance on this matter would be highly valued! Unfortunately, maintaining a constant power supply to the PLC is not a viable option.
I understand that calculations cannot be done without power, but I am interested in determining the duration of the power outage once our system is back up and running. Despite searching various forums, I have not found a definitive solution to this issue. Additionally, I have real-time clock functions available on this programmable logic controller (PLC) that may help in tracking the outage duration.
Instead of counting minutes, utilize timestamps and mathematical calculations to track downtime efficiently. Record the current time in an N file while running, including the hour and minute (and day if necessary for periods longer than 24 hours). Prior to executing the logic in the scan, use the first scan bit as a cue to determine the time difference and save the result. It is advisable to incorporate extra logic to store multiple power-off periods to prevent loss of data in case of multiple power cycles.
Alternatively, you have the option to track the duration of power-on time. This is the approach I typically take.
Setting up a secondary budget PLC, like a micro820, to operate alongside your primary one on a 24-hour basis can be a beneficial strategy. Implementing a UPS for this PLC is recommended, as it will consume minimal power. This secondary PLC will predominantly run timers during times when the plant is without power, allowing you to track downtime by recording it into an array register at regular intervals, whether daily or weekly. I concur with Joseph's viewpoint that having a second PLC in operation can offer advantages, as it ensures that scheduled record intervals remain uninterrupted.
Thank you for the great advice provided by plvlce! I will definitely give it a try and provide feedback on how it worked. Your input is much appreciated!
Your approach seems logical to me and successfully addresses the need to incorporate preventive maintenance sessions into your downtime calculations. It seems that the main issue is accurately calculating the Actual_Minutes_Since_Shiftchange following a powerup. One method could be putting an internal clock in the PLC that keeps track of the time, even when the power is off. Or, in a more low-tech way, making note of the exact time when the PLC is switched off and cross-checking with the time you resume power might also be feasible.
Hey there! I think your approach of factoring in the time without power into your downtime percentage calculation is a pretty solid one. If I'm understanding you correctly, the PLC_Counted_Minutes_Since_Shiftchange accounts for the working time, right? In that case, the Actual_Minutes_Since_Shiftchange should account for the total time of shift. Perhaps you could log the shift start time and end time in a secure location (like a time-stamped notebook or digitally saved record sheet) unaffected by power outages. You might also consider integrating a small UPS (Uninterruptible Power Supply) for the PLC just to keep the clock running, if possible. That way, you would have a more accurate representation of the total time per shift. Just suggestions, but I hope they help you out a bit!
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Answer: - One method involves calculating the PLC_Counted_Minutes_Since_Shiftchange and subtracting this from the Actual_Minutes_Since_Shiftchange to factor in time without power during preventive maintenance sessions.
Answer: - While maintaining a constant power supply to the PLC is not feasible, exploring alternative methods like the one mentioned above may help in accurate downtime analysis.
Answer: - By implementing a logical approach that involves tracking specific conditions and calculations, such as the one proposed in the thread, the Actual_Minutes_Since_Shiftchange can be calculated to incorporate power interruptions into downtime analysis.
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