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PLC Programming Example | Day of Week to debug

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This is a simple approach with intentional bugs in the solution to lab manual exercise in downloadable PLC Training Certificate course at https://bin95.com/allen-bradley-plc-programming.htm
Simple solution for tracking Day of week (Mon,tues, etc.) part of HVAC scenario 3 (page 109 of Lab Manual). Last rung comment also give 2 alternate solutions (newer plc solution, and complex formula solution.)

After you write into a PLC and debug, test (or you are having diffulty making it work on your PLC, see https://www.slideshare.net/bin95/plc-programming-example-day-of-week-answ for one possble working solution.

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PLC Programming Example | Day of Week to debug

  1. 1. Https://BIN95.com Simple Track Day of Week (M,T,W,T,F,S,S) © BIN95.com On day of loading, pre plug C5.30.acc with value equal to what the current day of week is. (this is program setup) It simple and only requires minimum maintenance. The counter resets its self when counter done bit fires. thus a virtual engine. So for example, it is wednesday when you load the program, set C5:30.acc to = 3. If it was a friday, you would C5:30.acc to = 5. (Some PLC/PAC may need counter preset set at 8 instead of 7.) 0000 EQU Equal Source A S:40 0< Source B 23 23< EQU Clock Calendar Hours EQU Equal Source A S:41 0< Source B 59 59< EQU Clock Calendar Minutes CU DN CTU Count Up Counter C5:30 Preset 7< Accum 0< CTU Day of week Counter (1=Mon,2=Tue,3=Wed, 4=Thu,5=Fri,6=Sat, 7=Sun) DOWCNT C5:30 DN Day of week Counter (1=Mon,2=Tue,3=Wed, 4=Thu,5=Fri,6=Sat, 7=Sun) DOWCNT/DN RES C5:30 Day of week Counter (1=Mon,2=Tue,3=Wed, 4=Thu,5=Fri,6=Sat, 7=Sun) DOWCNT From there on out, C5:30.acc will keep track of what day of the week it is. 0001 LIM Limit Test Low Lim 6 6< Test C5:30.ACC 0< High Lim 7 7< LIM Day of week Counter (1=Mon,2=Tue,3=Wed, 4=Thu,5=Fri,6=Sat, 7=Sun) DOWCNT.ACC B3:20 7 ON is Day of week equals SAT or SUN. (One time setup of C5:30.acc with day downloading. IE:3=w) With a huge Gregorian claendar mathimatical formula, you can do it another way that it also acocunts for leap years and does not require setup value be entered. 10 differant programmers, you could have 10 differnt ways to takle this one. Always opt for the simplist way when possible. Formula: N = d + 2m + [3(m+1)/5] + y + [y/4] - [y/100] + [y/400] + 2 ("d"=S:39, "m"=S:38, "y"=S:37, "N"=day of week 0-6) (On some PLC processor, you have a Status word you can use that already has value 0-6 for date. Like SLC 500/3-5 uses S:53, where 0=Sunday, 6=Saturday) 0002 B3:20 7 ON is Day of week equals SAT or SUN. (One time setup of C5:30.acc with day downloading. IE:3=w) B3:40 0 Do something, except sat and sun. 0003 END

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