Sensaphone SCADA 3000 Users manual - Manual (Page 183)

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Chapter 15: Ladder Logic Programming
LADDeR PROGRAm eXAmPLeS
example #1
The ladder program below (Figure 5) illustrates simple input to output control. If input 0 clos-
es, then output 0 will turn on. If Input 0 opens, then the output will turn off.
Figure 12: Simple input to output control
example #2
The following program (Figure 6) would be used to refill a tank when it becomes empty. Say
the tank has a float switch at the top to indicate that the tank is full, and a float switch at the
bottom to indicate that the tank is empty. When the level gets too low, the low-level float
switch opens, making the XIO instruction true, which latches the pump on. The pump will
stay on until the high-level switch closes, causing the XIC instruction to become true, which
unlatches the pump and turns it off.
Figure 13: Float Switch control
example #3
In this example, a timer is used to delay the start of a system by 10 seconds. When the system
power switch is turned on, the timer starts running. When it reaches the preset value, the
timer-done bit is set, which makes the XIC instruction on rung #2 true. This in turn activates
output 2, which turns on the system.