Hello all, I’m writing code in RsLogix 500 for a lift station pump control of two pumps, I will be using a PV + 700 as A HMI interface. I have a question about capturing and monitoring the level set points for the ON level and OFF level. I do want ensure that the operator does not enter a lower value for PUMP ON Set point then the OFF set point and vice-versa. Attached is the logic, LAD 3 rung 3 to 6 is what I wrote for now but I got a feeling there is a more efficient way of doing this, besides if the operator enters a lower value in N7:2 both message triggers will trip. Any help greatly appreciated.
Level Set-Point entry limit RsLogix 500
- Thread starter MJC
- Start date
dmargineau
Lifetime Supporting Member
These operational restrictions could be implemented either on the CPU level or within the HMI application.
Personally I prefer the latter option since most FTVS numeric WRITE objects (such as a Numeric Input Cursor Point) could be configured with Min/Max constant/variable limits.
Establish the numerical limits of the application (if the limits vary, decide which one will be the "master" value) and then implement them when configuring the HMI application's numerical WRITE objects, under the object's Numeric tab.
Personally I prefer the latter option since most FTVS numeric WRITE objects (such as a Numeric Input Cursor Point) could be configured with Min/Max constant/variable limits.
Establish the numerical limits of the application (if the limits vary, decide which one will be the "master" value) and then implement them when configuring the HMI application's numerical WRITE objects, under the object's Numeric tab.
Bit_Bucket_07
Member
If "Off Value" > 97 THEN
"Off Value" = 98
If "On Value" < "Off Value" THEN
"On Value" = "Off Value" + 2
It's easy enough to write this range check logic with Compares and Moves. Then you won't need alarm messages, because it will be impossible for an out of range setpoint alarm to occur.
"Off Value" = 98
If "On Value" < "Off Value" THEN
"On Value" = "Off Value" + 2
It's easy enough to write this range check logic with Compares and Moves. Then you won't need alarm messages, because it will be impossible for an out of range setpoint alarm to occur.
Use compare (GRT, LES, GEQ, LEQ) and Move (MOV) instructions to move the minimum or maximum value back into the setpoint if the setpoint exceeds either.
Example:
N7:0 is your setpoint, N7:1 is the maximum value of that setpoint. Make an equivalent rung for your minimum value.
Example:
|----GRT ----------MOV -----|
Src A = N7:0 Src A = N7:1
Src B = N7:1 Src B = N7:0
N7:0 is your setpoint, N7:1 is the maximum value of that setpoint. Make an equivalent rung for your minimum value.
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