A drip irrigation zone application divides an agricultural field or garden into multiple irrigation zones, allowing each zone to be watered independently based on crop requirements, soil moisture, and water availability.
Key functions:
Zone Control: Operates solenoid valves to control water flow to individual zones.
Automation: Uses a PLC or irrigation controller to schedule irrigation cycles.
Sensor Monitoring: Monitors soil moisture, water pressure, and flow rate.
Water Efficiency: Delivers water directly to plant roots, reducing water wastage.
Protection: Detects low pressure, leakage, or abnormal flow and generates alarms.
HMI/SCADA Monitoring: Displays zone status, irrigation time, and sensor readings.
Functional schematic overview for the PLC
application.
I/O and Internal Tags
|
Area |
Tag |
Type |
Default |
Description |
|
INPUT |
AutoMode |
Bool |
|
|
|
INPUT |
StartPB |
Bool |
|
|
|
INPUT |
StopPB |
Bool |
|
|
|
INPUT |
ResetPB |
Bool |
|
|
|
INPUT |
EStopOK |
Bool |
|
|
|
INPUT |
SensorIn |
Bool |
|
|
|
INPUT |
SensorDone |
Bool |
|
|
|
INPUT |
ActuatorHome |
Bool |
|
|
|
INPUT |
ActuatorExtended |
Bool |
|
|
|
INPUT |
Step1Time |
Time |
T#1s |
|
|
INPUT |
Step2Time |
Time |
T#3s |
|
|
INPUT |
Step3Time |
Time |
T#1s |
|
|
INPUT |
TimeoutTime |
Time |
T#20s |
|
|
OUTPUT |
ConveyorRun |
Bool |
|
|
|
OUTPUT |
ClampOutput |
Bool |
|
|
|
OUTPUT |
ProcessOutput |
Bool |
|
|
|
OUTPUT |
DischargeOutput |
Bool |
|
|
|
OUTPUT |
CycleActive |
Bool |
|
|
|
OUTPUT |
CycleDonePulse |
Bool |
|
|
|
OUTPUT |
Fault |
Bool |
|
|
|
OUTPUT |
StepNo |
Int; |
|
0 idle, 10
wait/index, 20 clamp, 30 process, 40 discharge |
|
VAR |
AutoMode |
Bool |
|
|
|
VAR |
StartPB |
Bool |
|
|
|
VAR |
StopPB |
Bool |
|
|
|
VAR |
ResetPB |
Bool |
|
|
|
VAR |
EStopOK |
Bool |
|
|
|
VAR |
SensorIn |
Bool |
|
|
|
VAR |
SensorDone |
Bool |
|
|
|
VAR |
ActuatorHome |
Bool |
|
|
|
VAR |
ActuatorExtended |
Bool |
|
|
|
VAR |
Step1Time |
Time |
T#1s |
|
|
VAR |
Step2Time |
Time |
T#3s |
|
|
VAR |
Step3Time |
Time |
T#1s |
|
|
VAR |
TimeoutTime |
Time |
T#20s |
|
SCL Program
// Application 111: Drip Irrigation Zone
// Category: Agriculture
// PLC: Siemens S7-1200
// Language: SCL for TIA Portal
// Note: Training template. Validate all safety and
machine behavior before commissioning.
FUNCTION_BLOCK "FB_111_DripIrrigationZone"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 1.0
VAR_INPUT
AutoMode :
Bool;
StartPB : Bool;
StopPB : Bool;
ResetPB : Bool;
EStopOK : Bool;
SensorIn :
Bool;
SensorDone :
Bool;
ActuatorHome :
Bool;
ActuatorExtended : Bool;
Step1Time :
Time := T#1s;
Step2Time :
Time := T#3s;
Step3Time :
Time := T#1s;
TimeoutTime :
Time := T#20s;
END_VAR
VAR_OUTPUT
ConveyorRun :
Bool;
ClampOutput :
Bool;
ProcessOutput :
Bool;
DischargeOutput
: Bool;
CycleActive :
Bool;
CycleDonePulse
: Bool;
Fault : Bool;
StepNo : Int;
// 0 idle, 10 wait/index, 20 clamp, 30 process, 40 discharge
END_VAR
VAR
RunLatch :
Bool;
Step1Timer :
TON;
Step2Timer :
TON;
Step3Timer :
TON;
TimeoutTimer :
TON;
END_VAR
BEGIN
CycleDonePulse
:= FALSE;
IF ResetPB AND
EStopOK THEN
Fault :=
FALSE;
StepNo :=
0;
END_IF;
IF StopPB OR
NOT EStopOK OR Fault OR NOT AutoMode THEN
RunLatch :=
FALSE;
StepNo :=
0;
ELSIF StartPB
AND AutoMode THEN
RunLatch :=
TRUE;
END_IF;
IF RunLatch AND
(StepNo = 0) THEN
StepNo :=
10;
END_IF;
Step1Timer(IN
:= StepNo = 20, PT := Step1Time);
Step2Timer(IN
:= StepNo = 30, PT := Step2Time);
Step3Timer(IN
:= StepNo = 40, PT := Step3Time);
TimeoutTimer(IN
:= RunLatch AND (StepNo <> 0), PT := TimeoutTime);
CASE StepNo OF
10:
IF
SensorIn AND ActuatorHome THEN
StepNo := 20;
END_IF;
20:
IF
Step1Timer.Q OR ActuatorExtended THEN
StepNo := 30;
END_IF;
30:
IF
SensorDone OR Step2Timer.Q THEN
StepNo := 40;
END_IF;
40:
IF
Step3Timer.Q THEN
CycleDonePulse := TRUE;
StepNo := 10;
END_IF;
END_CASE;
IF
TimeoutTimer.Q THEN
Fault :=
TRUE;
RunLatch :=
FALSE;
StepNo :=
0;
END_IF;
ConveyorRun :=
RunLatch AND ((StepNo = 10) OR (StepNo = 40));
ClampOutput :=
RunLatch AND ((StepNo = 20) OR (StepNo = 30));
ProcessOutput
:= RunLatch AND (StepNo = 30);
DischargeOutput
:= RunLatch AND (StepNo = 40);
CycleActive :=
RunLatch AND (StepNo <> 0);
END_FUNCTION_BLOCK
Commissioning reminder: validate all I/O mapping,
permissive behavior, feedback wiring, emergency-stop circuits, and local safety
requirements before running real equipment.
Commissioning Checklist
·
Map every PLC tag to the correct
physical input, output, HMI tag, or memory address.
·
Compile in TIA Portal and adjust
tag names, timers, and setpoints for the real machine.
·
Test normal sequence, stop, reset,
feedback failure, timeout, and alarm conditions in simulation first.
·
Use certified safety hardware or
fail-safe logic for emergency stops, guards, and hazardous motion.