Water Level Controller And Motor Protector

Many a time we forget to switch off the motor pushing water into the overhead tank (OHT) in our households. As a result, water keeps overflowing until we notice the overflow and switch the pump off
As the OHT is usually kept on the topmost floor, it is cumbersome to go up frequently to check the water level in the OHT.

Here’s a microcontroller-based water level controller-cum-motor protector to solve this problem. It controls ‘on’ and ‘off ’ conditions of the motor depending upon the level of water in the tank. The status is displayed on an LCD module. The circuit also protects the motor from high voltages, low voltages, fluctuations of mains power and dry running.

Circuit description

Fig. 1 shows the circuit of the microcontroller-based water level controller-cum-motor protector. It comprises operational amplifier LM324, microcontroller AT89C51, optocoupler PC817, regulator 7805, LCD module and a few discrete components. 
  
The AT89C51 (IC2) is an 8-bit microcontroller with four ports (32 I/O lines), two 16-bit timers/ counters, on-chip oscillator and clock circuitry. Eight pins of port-1 and three pins of port-3 are interfaced with data and control lines of the LCD module. Pins P3.0, P3.1 and P3.6 are connected to RS (pin 4), R/W (pin 5) and E (pin 6) of the LCD, respectively. Pin EA (pin 31) is strapped to V_cc for internal program executions. Switch S2 is used for backlight of the LCD module.
  
Power-on-reset is achieved by connecting capacitor C8 and resistor R14 to pin 9 of the microcontroller. Switch S1 is used for manual reset.
  
The microcontroller is operated with a 12MHz crystal. Port pins P2.0 through P2.2 are used to sense the water level, while pins P2.3 and P2.4 are used to sense the under-voltage and over-voltage, respectively. Pin P3.4 is used to control relay RL1 with the help of optocoupler IC3 and transistor T5 in the case of under-voltage, over-voltage and different water level conditions. Relay RL1 operates off a 12V supply. Using switch S3, you can manually switch on the motor.
The LM324 (IC1) is a quad operational amplifier (op-amp). Two of its op-amps are used as comparators to detect under- and over-voltage. In normal condition, output pin 7 of IC1 is low, making pin P2.3 of IC2 high. When the voltage at pin 6 of N1 goes below the set reference voltage at pin 5 (say, 170 volts), output pin 7 of N1 goes high. This high output makes pin P2.3 of IC2 low, which is sensed by the microcontroller and the LCD module shows ‘low voltage.’

In normal condition, pin 1 of N2 is high. When the voltage at pin 2 of N2 goes above the set voltage at pin 3, output pin 1 of N2 goes low. This low signal is sensed by the microcontroller and the LCD module shows ‘high voltage.’

Presets VR1 and VR2 are used for calibrating the circuit for under-and over-voltage, respectively.   
The AC mains is stepped down by transformer X1 to deliver a secondary output of 12V at 500 mA. The transformer output is rectified by a full-wave bridge rectifier comprising diodes D5 through D8, filtered by capacitor C2, and used for the under- and over-voltage detection circuitry.
  
The transformer output is also rectified by a full-wave bridge rectifier comprising diodes D1 through D4, filtered by capacitor C1 and regulated by IC4 to deliver regulated 5V for the circuit.
 
When water in the tank rises to come in contact with the sensor, the base of transistor BC548 goes high. This high signal drives transistor BC548 into saturation and its collector goes low. The low signal is sensed by port pins of microcontroller IC2 to detect empty tank, dry sump and full tank, respectively.
     
Operation

When water in the tank is below sensor A, the motor will switch on to fill water in the tank. The LCD module will show ‘motor on.’ The controller is programmed for a 10-minute time interval to check the dry-run condition of the motor. If water reaches sensor B within 10 minutes, the microcontroller comes out of the dry-run condition and allows the motor to keep pushing water in the tank.

The motor will remain ‘on’ until water reaches sensor C. Then it will stop automatically and the microcontroller will go into the standby mode. The LCD module will show ‘tank full’ followed by ‘standby mode’ after a few seconds. The ‘standby mode’ message is displayed until water in the tank goes below sensor A. 
  
In case water does not reach sensor B within 10 minutes, the microcontroller will go into the dry-running mode and stop the motor for 5 minutes, allowing it to cool down. The LCD module will show ‘dry-sump1.’
  
After five minutes, the microcontroller will again switch on the motor for
10 minutes and check the status at sensor B. If water is still below sensor B, it will go into the dry-running mode and the LCD module will show ‘dry-sump2.’
  
The same procedure will repeat, and if the dry-run condition still persists, the display will show ‘dry-sump3’ and the microcontroller will not start the motor automatically. Now you have to check the line for water and manually reset the microcontroller to start operation.
  
In the whole procedure, the microcontroller checks for high and low voltages. For example, when the voltage is high, it will scan for about two seconds to check whether it is a fluctuation. If the voltage remains high after two seconds, the microcontroller will halt running of the motor. Now it will wait for the voltage to settle down. After the voltage becomes normal, it will still check for 90 seconds whether the voltage is normal or not. After normal condition, it will go in the standby mode and start the aforementioned procedure.

Code:

$MOD51 START: LJMP MAIN_PGR ;GO TO MAIN PROGRAMME ORG 002FH MAIN_PGR: MOV A, # 38H ;INITIALIZE LCD LCALL WR_LCD MOV A, #0FH LCALL WR_LCD MOV A, #06H LCALL WR_LCD MOV A, #01H LCALL WR_LCD MOV A, #80H LCALL WR_LCD MOV A, #53H ;WRITE DATA TO LCD LCALL LCD_RAM ;i.e.,” STANDBY-MODE” MOV A, #54H LCALL LCD_RAM MOV A, #41H LCALL LCD_RAM MOV A, #4EH LCALL LCD_RAM MOV A, #44H LCALL LCD_RAM MOV A, #42H LCALL LCD_RAM MOV A, #59H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #0C0H ;JUMP TO 9TH POSITION LCALL WR_LCD ;OR SECOND LINE MOV A, #4DH ;ENTER DATA AGAIN LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #44H LCALL LCD_RAM MOV A, #45H LCALL LCD_RAM LJMP SCAN ;GO TO 010AH ORG 00A0H WR_LCD: LCALL SETT ;CHECK FOR READY STATUS OF LCD MOV P1,A ;MOVE CONTENTS OF A TO PORT 1 CLR P3.0 ;WRITE COMMANDS TO LCD CLR P3.1 SETB P3.6 CLR P3.6 RET ;RETURN TO PROGRAMME ORG 00C0H LCD_RAM: LCALL SETT ;CHECK READY STATUS OF LCD MOV P1,A ;MOVE CONTENS OF A TO PORT 1 SETB P3.0 ;WRITE TO DISPLAY RAM OF LCD CLR P3.1 SETB P3.6 CLR P3.6 RET ;GO TO PROGRAMME ORG 00F0H SETT: CLR P3.6 MOV P1, #0FFH ;SET PORT1 FOR INPUT NOP ;DELAY CLR P3.0 SETB P3.1 L1: CLR P3.6 SETB P3.6 JB P1.7,L1 ;IF NOT READY JUMP TO 00FA H CLR P3.6 RET ;BACK TO PROGRAMME ORG 010AH SCAN: SETB 76H ;SET USER FLAGS SETB 77H SETB 78H MOV P2,#0FFH ;SET PORT2 FOR INPUT L4: JNB P2.4,L2 ;IF H/V THEN GOTO 0136 H JNB P2.3,L3 ;IF L/V THEN GOTO 018B H JNB P2.0,L4 ;SCAN FOR TANK TO BE EMPTY SJMP L130 ;GOTO 0130 H LOOP: LCALL TMR_10MIN ;CALL 10 MIN. TIMER JNB 78H,L3 ;L/V THEN GOTO 018B H JNB 77H,L2 ;H/V THEN GOTO 0136 H JB 76H,L5 ;DRY SUMP THEN GOTO 0188 H JB P2.2,$ ;WAIT UNTILL TANK FULL LOOP1:LJMP TANK_FULL ;GOTO TANK FULL DISPLAY L130: CLR P3.4 ;START MOTOR LJMP DIS_M_ON ;DISPLAY MOTOR ON NOP ;BLANK SPACE L2: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.4,L4 ;STILL H/V THEN GOTO 0113 H LOOP2:SETB P3.4 ;H/V THEN OFF MOTOR NOP NOP LCALL INI_LCD ;INITIALIZE LCD MOV A, #48H ;DISPLAY HIGH-VOLTAGE LCALL LCD_RAM MOV A, #49H LCALL LCD_RAM MOV A, #47H LCALL LCD_RAM MOV A, #48H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #56H LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #04CH LCALL LCD_RAM MOV A, #0C0H ;MOVE TO 9TH CHARACTER LCALL WR_LCD MOV A, #54H LCALL LCD_RAM MOV A, #41H LCALL LCD_RAM MOV A, #47H LCALL LCD_RAM MOV A, #45H LCALL LCD_RAM LJMP CHK_HV ;GOTO 0490 H NOP ;BLANK SPACE L5: LJMP M_STOP ;GOTO 0226 H L3: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.3,L4 ;VOLTAGE OK THEN GOTO 0113 H LOOP3:SETB P3.4 ;STOP MOTOR IF ON LCALL INI_LCD ;INITIALIZE LCD MOV A, #04CH ;DISPLAY LOW-VOLTAGE LCALL LCD_RAM MOV A, #04FH LCALL LCD_RAM MOV A, #57H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #56H LCALL LCD_RAM MOV A, #04FH LCALL LCD_RAM MOV A, #04CH LCALL LCD_RAM MOV A, #54H LCALL LCD_RAM MOV A, #0C0H ;GOTO 9TH CHARACTER LCALL WR_LCD MOV A, #41H ;START DISPLAY AGAIN LCALL LCD_RAM MOV A, #47H LCALL LCD_RAM MOV A, #45H LCALL LCD_RAM LJMP CHK_LV ;GOTO 04B0 H NOP NOP NOP ORG 01D8H DLY_2SEC: MOV R3, #03H L8: MOV R4, #0FFH L7: MOV R5, #0FFH L6: NOP NOP NOP NOP NOP NOP DJNZ R5,L6 ;01DEH DJNZ R4,L7 ;01DCH DJNZ R3,L8 ;01DAH RET ;BACK TO PROGRAMME ORG 0226H M_STOP: SETB P3.4 ;STOP MOTOR LCALL INI_LCD ;INITIALIZE LCD MOV A, #44H ;START FILLING DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #52H LCALL LCD_RAM MOV A, #59H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #53H LCALL LCD_RAM MOV A, #055H LCALL LCD_RAM MOV A, #04DH LCALL LCD_RAM MOV A, #50H LCALL LCD_RAM MOV A, #0C0H ;MOVE TO 9TH CHARACTER OF LCD LCALL WR_LCD MOV A, #31H ;START WRITING AGAIN LCALL LCD_RAM LJMP L300 ;GOTO 0300 H TANK_FULL: SETB P3.4 ;STOP MOTOR NOP ;BLANK SPACES FOR FURTHER EXPANSION NOP NOP NOP NOP NOP NOP LCALL INI_LCD ;INITIALIZE LCD MOV A, #54H ;WRITE TO DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #41H LCALL LCD_RAM MOV A, #4EH LCALL LCD_RAM MOV A, #4BH LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #46H LCALL LCD_RAM MOV A, #55H LCALL LCD_RAM MOV A, #4CH LCALL LCD_RAM MOV A, #0C0H ;GOTO 9TH CHARACTER OF LCD LCALL WR_LCD MOV A, #4CH ;START DISPLAYING AGAIN LCALL LCD_RAM LCALL DLY_2SEC ;DISPLAY IT FOR 2 SECONDS LJMP START ;GOTO STANDBY MODE ORG 02B3H INI_LCD:MOV A, # 38H LCALL WR_LCD MOV A, #0FH LCALL WR_LCD MOV A, #06H LCALL WR_LCD MOV A, #01H LCALL WR_LCD MOV A, #80H LCALL WR_LCD RET ;BACK TO PROGRAMME NOP NOP NOP DIS_M_ON: LCALL INI_LCD ;INITIALIZE LCD MOV A, # 4DH ;WRITE INTO DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #04FH LCALL LCD_RAM MOV A, #54H LCALL LCD_RAM MOV A, #04FH LCALL LCD_RAM MOV A, #52H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #04FH LCALL LCD_RAM MOV A, #04EH LCALL LCD_RAM LJMP LOOP ;BACK TO MAIN PROGRAMME AT 011E H NOP NOP L300: LCALL TMR_5MIN ;CALL 5 MINUTES TIMER LJMP MAIN ;GOTO MAIN PROGRAMME AT 0550 H ORG 0320H TMR_5MIN: MOV R2,#03H L12: MOV R3, #0FFH L11: MOV R4, #0FFH L10: MOV R5, #0FFH L9: NOP NOP NOP NOP DJNZ R5, L9 ;0328 DJNZ R4, L10 ;0326 DJNZ R3, L11 ;0324 DJNZ R2, L12 ;0322 RET ;BACK TO MAIN PROGRAMME ORG 0430H L430: JNB P2.2,L43C ;IF TANK FULL GOTO 043C H JNB P2.4,L43F ;H/V THEN GOTO 043F H L436: JNB P2.3,L448 ;L/V THEN GOTO 0448 H L439: SJMP L430 ;GOTO 0430 H NOP L43C: LJMP LOOP1 ;ACK TO MAIN PROGRAMME L43F: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.4, L436 ;IF NOT H/V THEN GOTO 0436 H LJMP LOOP2 ;H/V THEN GOTO 013C H L448: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.3, L439 ;IF NOT L/V THEN GOTO 0439 H LJMP LOOP3 ;IF L/V THEN GOTO 0191 H ORG 0490H CHK_HV: NOP NOP L492: LCALL DLY_2MIN ;WAIT FOR 2 MINUTES JNB P2.4,L492 ;CHECK FOR H/V AGAIN LJMP START ;GOTO START AGAIN ORG 04B0H CHK_LV: NOP NOP L4B2: LCALL DLY_2MIN ;WAIT FOR 2 MINUTES JNB P2.3, L4B2 ;CHECK FOR L/V AGAIN LJMP START ;GOTO START AGAIN ORG 0500H DLY_2MIN: MOV R2, #0FFH L502: MOV R3,#0FFH L504: MOV R4,#0FFH L506: NOP NOP NOP NOP DJNZ R4, L506 DJNZ R3, L504 DJNZ R2, L502 RET ;BACK TO MAIN PROGRAMME ORG 054DH M_START: LJMP SUB_BR ;SUB BRANCH DUE TO SPACE PROBLEM MAIN: JNB P2.4, L59A ;CHECK FOR HIGH VOLTAGE JNB P2.3, L5A3 ;CHECK FOR LOW VOLTAGE CLR P3.4 ;IF VOLTAGE OK THEN START MOTOR LCALL INI_LCD ;INITIALIZE LCD MOV A, #04DH ;START WRITING TO DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #04FH LCALL LCD_RAM MOV A, #54H LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #52H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #4EH LCALL LCD_RAM LCALL TMR_10MIN ;ENTER INTO 10 MINUTES TIMER JNB 78H, C_LV; 05A9H ;LOW VOLTAGE THEN GOTO 05A9 H JNB 77H, C_HV; 05A0H ;HIGH VOLTAGE THEN GOTO 05A0 H JB 76H, DRY ;05ACH ;IF TANK DRY THEN GOTO 05AC H L58F: JNB P2.2, M_START ;TANK FULL THEN GOTO 054D H JNB P2.4, L59A ;HIGH VOLTAGE THENGOTO 059A H L595: JNB P2.3, L5A3 ;LOW VOLTAGE THEN GOTO 05A3 H L598: SJMP L58F ;REPEAT FROM 058F H L59A: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.4, L595 ;IF NOT H/V THEN GO BACK TO 0595 H C_HV: LJMP LOOP2 ;STILL H/V THEN GOTO 013C H L5A3: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.3, L598 ;IF NOT L/V THEN GO BACK TO 0598 H C_LV: LJMP LOOP3 ;STILL L/V THEN GOTO 0191 H DRY: SETB P3.4 ;STOP MOTOR LCALL INI_LCD ;INITIALIZE LCD MOV A, #44H ;START WRITING TO DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #52H LCALL LCD_RAM MOV A, #59H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #53H LCALL LCD_RAM MOV A, #55H LCALL LCD_RAM MOV A, #4DH LCALL LCD_RAM MOV A, #50H LCALL LCD_RAM MOV A, #0C0H ;GOTO 9TH CHARACTER OF LCD LCALL WR_LCD MOV A, #32H ;START WRITING AGAIN LCALL LCD_RAM LCALL TMR_5MIN ;WAIT FOR 5 MINUTES JNB P2.4,HV ; 0630H ;H/V THEN GOTO 0630 H JNB P2.3,LV ; 0639H ;L/V THEN GOTO 0639 H CLR P3.4 ;IF VOLTAGE OK THEN START MOTOR LCALL INI_LCD ;INITILIZE LCD MOV A, #4DH ;START WRITING TO DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #54H LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #52H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #4FH LCALL LCD_RAM MOV A, #4EH LCALL LCD_RAM LCALL TMR_10MIN ;GOTO MINUTES TIMER JNB 78H, L63F ;L/V THEN GOTO 063F H JNB 77H, L636 ;H/V THEN GOTO 0636 JB 76H, L647 ;STILL DRY SUMP THEN GOTO 0647 H L625: JNB P2.2, SUB_BR ;0642H ;TANK FULL THEN GOTO 0642 H JNB P2.4, HV ;0630H ;H/V THEN GOTO 0630 H N_HV: JNB P2.3, LV ;0639H ;L/V THEN GOTO 0639 H N_LV: SJMP L625 ;REPEAT FROM 0625 H HV: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.4, N_HV ;062BH ;IF NOT H/V THEN GOTO 062B H L636: LJMP LOOP2 ;STILL H/V THEN GOTO 013C H LV: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JB P2.3, N_LV ;062EH ;IF NOT L/V THEN GOTO 062E H L63F: LJMP LOOP3 ;STILL L/V THEN GOTO 0191 H SUB_BR: SETB P3.4 ;STOP MOTOR LJMP TANK_FULL ;TANK FULL THEN GOTO 0260 H L647: SETB P3.4 ;STOP MOTOR NOP NOP LCALL INI_LCD ;INITIALIZE LCD MOV A, #44H ;START WRITING TO DISPLAY RAM OF LCD LCALL LCD_RAM MOV A, #52H LCALL LCD_RAM MOV A, #59H LCALL LCD_RAM MOV A, #0B0H LCALL LCD_RAM MOV A, #53H LCALL LCD_RAM MOV A, #55H LCALL LCD_RAM MOV A, #4DH LCALL LCD_RAM MOV A, #50H LCALL LCD_RAM MOV A, #0C0H ;GOTO 9TH CHARACTER OF LCD LCALL WR_LCD MOV A, #33H ;START WRITING AGAIN LCALL LCD_RAM SJMP $ ;STAY HERE UNTILL MANUAL RESET ORG 0750H TMR_10MIN: MOV R2, #05H L752: MOV R3, #0FFH L754: MOV R4, #0FFH L756: MOV R5, #0FFH L758: NOP NOP NOP NOP NOP DJNZ R5, L758 DJNZ R4, L756 JNB P2.4,L770 ;H/V THEN GOTO 0670 H L764: JNB P2.3, L778 ;L/V THEN GOTO 0678 H L767: JNB P2.1, L780 ; NOT DRY SUMP THEN GOTO 0680 H L76A: DJNZ R3, L754 DJNZ R2, L752 RET ;BACK TO MAIN PROGRAMME NOP L770: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JNB P2.4, 0788H ;STILL H/V THEN GOTO 0788 H SJMP L764 ; NOT H/V THEN GOTO 0764 H L778: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JNB P2.3, 078BH ;STILL L/V THEN GOTO 078B H SJMP L767 ;NOT L/V THEN GOTO 0767 H L780: LCALL DLY_2SEC ;WAIT FOR 2 SECONDS JNB P2.1, 078EH ;STILL NOT DRY SUMP THEN GOTO 078E H SJMP L76A ;OTHERWISE GOTO 076A CLR 77H ;CLEAR FLAG 77H FOR H/V RET CLR 78H ;CLEAR FLAG 78H FOR L/V RET CLR 76H ;CLEAR FLAG 76H FOR DRY SUMP CHECK RET END