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Ladder program examples, Ladder program examples -27 – Sensaphone SCADA 3000 Users manual User Manual

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15-27

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.