In the previous section, we configured the timer “T4:1” to time for 20 seconds after the Ball Mill motor starts. If the motor stops for any reason, we will need to determine if the motor has run for the 20-second time period.
A TON timer is reset when the input logic to the timer is false, so if the motor stops, I will lose the accumulated time and the “Done” bit if it is has been set.
A Retentive Timer On, or RTO, will retain its timer memory even if the input logic is false.
So, Right-click on the TON instruction label and select “Change Instruction Type” from the menu. Type in RTO and the instruction is updated, preserving the previously configured values.
We want to use the timer logic to satisfy the rest of the second program requirement. The oil pump should stop if the Ball Mill motor stops when it has been running less than 20 seconds, but the fan should run an additional 5 seconds.
We will take advantage of the properties of a Timer Off instr...
We will look at the third specification for the program:
"If the Mill has operated for more than 20 seconds, the fan should remain on until reset by a separate fan reset button, and the oil pump should remain on for an additional 10 seconds after the Mill is turned off."
We will program the log...
The fourth program requirement requires if the Mill motor temperature goes above 80 degrees C, the mill should be stopped to protect the windings.
The input from the temperature transmitter will need to be scaled to produce a value in engineering units, in this case, degrees C.
The “SCALING” in...
