Moisture sensing automatic plant watering system using 8051.

Automatic plant watering system.

This project is about a moisture sensing automatic plant watering system using 8051 microcontroller. The system simply senses the moisture level and switches on the irrigation pump when the moisture is below the set limit. The system switches off the pump when the moisture rises above the set point. The moisture level threshold can be set using a trimpot on the system. The status of the pump (whether ON or OFF) is displayed on a 16×2 LCD display. The system can be divided into three section as follows.

Sensing prob.

YL 69 moisture sensing probe is used to sense the moisture here. It is simply a fork shaped PCB with tracks running on both sides of the legs. Just plug this probe in to the soil where you want to sense the moisture. Image of the YL 69 sensing probe is given below.

Comparator circuit.

YL 38 comparator module is used in this project. It is a single channel opamp comparator based on L393 IC. This module just compares the output voltage of the sensing probe with a reference voltage and switches its voltage appropriately for the microcontroller to read. Circuit diagram of the YL 38 comparator module is shown below.

Output voltage of the sensing probe is connected to the inverting input of the opamp. When the moisture level is high more current passes through the sensing probe and so the voltage at the inverting pin will be higher than the reference. The reference can be set using the trimpot R2. At this condition output of the opamp goes low and sinks the LED D1 to make it glow. When the moisture is lower than the set point, the opposite happens. So in simple words, a LOW output of the opamp indicates a high moisture and a HIGH output of the opamp indicates a low moisture. Output of the opamp is marked as pin D0 on the sensor YL 38 module. This pin is connected to the microcontroller for further processing. LED D2 is just a power ON indicator. Capacitors C1 and C2 are noise filters.

Microcontroller section.

Microcontroller section senses the status of the comparator module and switches the irrigation motor appropriately. It also displays the status of the pump on the LCD screen. The power supply unit and the motor driver unit are incorporated in this section. Full circuit diagram of the project is given below.

Output pin of the comparator module (D0) is connected to P3.5 pin of the 8051 microcontroller. The microcontroller monitors the moisture level by polling the status of the P3.5 pin which is the output of the comparator.

Program.

RS EQU P2.7  RW EQU P2.6  E  EQU P2.5    ORG 00H  SETB P3.5  MOV TMOD,#00000001B   MAIN:ACALL DINT       ACALL TEXT1       JB P3.5, NEXT       ACALL LINE2       ACALL TEXT2       CLR P2.0       SJMP EXIT  NEXT:ACALL LINE2       ACALL TEXT3       SETB P2.0       EXIT:ACALL DELAY1  SJMP MAIN      DELAY1:MOV R0,#15D  BACK1: MOV TH0,#00000000B            MOV TL0,#00000000B            SETB TR0               HERE2: JNB TF0,HERE2                  CLR TR0                      CLR TF0                      DJNZ R0,BACK1         RET          TEXT1: MOV A,#"M"      ACALL DISPLAY      MOV A,#"o"      ACALL DISPLAY      MOV A,#"i"      ACALL DISPLAY      MOV A,#"s"      ACALL DISPLAY      MOV A,#"t"      ACALL DISPLAY      MOV A,#"u"      ACALL DISPLAY      MOV A,#"r"      ACALL DISPLAY      MOV A,#"e"      ACALL DISPLAY      MOV A,#" "      ACALL DISPLAY      MOV A,#"C"      ACALL DISPLAY      MOV A,#"o"      ACALL DISPLAY      MOV A,#"n"      ACALL DISPLAY      MOV A,#"t"      ACALL DISPLAY      MOV A,#"r"      ACALL DISPLAY      MOV A,#"o"      ACALL DISPLAY      MOV A,#"l"      ACALL DISPLAY      RET         TEXT2: MOV A,#"["      ACALL DISPLAY       MOV A,#"O"      ACALL DISPLAY      MOV A,#"K"      ACALL DISPLAY      MOV A,#"]"      ACALL DISPLAY      MOV A,#" "      ACALL DISPLAY      MOV A,#"P"      ACALL DISPLAY      MOV A,#"u"      ACALL DISPLAY      MOV A,#"m"      ACALL DISPLAY      MOV A,#"p"      ACALL DISPLAY      MOV A,#" "      ACALL DISPLAY      MOV A,#"O"      ACALL DISPLAY      MOV A,#"F"      ACALL DISPLAY      MOV A,#"F"      ACALL DISPLAY      RET         TEXT3: MOV A,#"["      ACALL DISPLAY      MOV A,#"L"      ACALL DISPLAY      MOV A,#"o"      ACALL DISPLAY      MOV A,#"w"      ACALL DISPLAY      MOV A,#"]"      ACALL DISPLAY      MOV A,#" "      ACALL DISPLAY      MOV A,#"P"      ACALL DISPLAY      MOV A,#"u"      ACALL DISPLAY      MOV A,#"m"      ACALL DISPLAY      MOV A,#"p"      ACALL DISPLAY      MOV A,#" "      ACALL DISPLAY      MOV A,#"O"      ACALL DISPLAY      MOV A,#"N"      ACALL DISPLAY      RET                   DINT:MOV A,#0CH       ACALL CMD      MOV A,#01H       ACALL CMD      MOV A,#06H       ACALL CMD      MOV A,#80H       ACALL CMD      MOV A,#3CH       ACALL CMD      RET    LINE2:MOV A,#0C0H       ACALL CMD      RET       CMD: MOV P0,A      CLR RS      CLR RW      SETB E      CLR E      ACALL DELAY      RET    DISPLAY:MOV P0,A      SETB RS      CLR RW      SETB E      CLR E      ACALL DELAY      RET    DELAY: CLR E      CLR RS      SETB RW      MOV P0,#0FFH      SETB E      MOV A,P0      JB ACC.7,DELAY      CLR E      CLR RW      RET     END            

About the program.

will be added soon