The rotary shaft encoder produces 42 pulses during the elevator cars movement between the first and second floor. So if on the first, and the second floor call button is pressed, the encoder will provide 42 pulses when the car moves from floor one, to floor two as well as travel from floor two to floor one.
m using a CTD count down counter in my plc program. how do i stop it from going past 0? it ends up going -1.-2 etc?? what instruction do i use its a parking lot application so
+Master Mo Hello, you could use a "less than" block with an RES instruction on the output rung side of a new rung. Use the ACC value of the counter and a hard ZERO to populate the comparison instruction. That way, if for any reason, your down counter is at an ACC value of zero, and you get another trigger for it, the counter will be reset and the ACC value will get set back to zero. Without seeing your program, it is difficult to say, but I often use and RES instruction. You could also limit the trigger to only impact on the counter if the ACC value is 1 or greater as an alternate option. Again, without seeing your program it is difficult to say, but either of these suggestions should work. You could also use the DN bit of the counter to trigger an RES instruction with your PRE set to zero.
techtrainingonline thanks alot! Its a parking lot application. So ctd represents how many cars have left the parking lot. The program instructions are that its not allowed to go below zero. (Its working in conjunction with and ctu counter)
+Master Mo In that case, I would use the option that will restrict the CTD from being triggered if the ACC value is not Greater than or Equal to 1. In this way, when the ACC value reaches 0, the CTD cannot be triggered again. I think the simple comparison type block would be the simplest option. Just put it in from of the CTD counter.
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could this be used for multi-floor elevators e.g. a 4 flr one?
why did you use the number 42 for the preset value?
The rotary shaft encoder produces 42 pulses during the elevator cars movement between the first and second floor.
So if on the first, and the second floor call button is pressed, the encoder will provide 42 pulses when the car moves from floor one, to floor two as well as travel from floor two to floor one.
m using a CTD count down counter in my plc program.
how do i stop it from going past 0? it ends up going -1.-2 etc?? what instruction do i use
its a parking lot application so
+Master Mo Hello, you could use a "less than" block with an RES instruction on the output rung side of a new rung. Use the ACC value of the counter and a hard ZERO to populate the comparison instruction. That way, if for any reason, your down counter is at an ACC value of zero, and you get another trigger for it, the counter will be reset and the ACC value will get set back to zero. Without seeing your program, it is difficult to say, but I often use and
RES instruction. You could also limit the trigger to only impact on the counter if the ACC value is 1 or greater as an alternate option. Again, without seeing your program it is difficult to say, but either of these suggestions should work.
You could also use the DN bit of the counter to trigger an RES instruction with your PRE set to zero.
techtrainingonline thanks alot!
Its a parking lot application. So ctd represents how many cars have left the parking lot. The program instructions are that its not allowed to go below zero.
(Its working in conjunction with and ctu counter)
+Master Mo In that case, I would use the option that will restrict the CTD from being triggered if the ACC value is not Greater than or Equal to 1. In this way, when the ACC value reaches 0, the CTD cannot be triggered again. I think the simple comparison type block would be the simplest option. Just put it in from of the CTD counter.
nice