Water level controller using 8051
A water level controller based using
8051 is shown in this article. A lot of water level controller projects
have been published in this website but the is the first one based on a
microcontroller. This water level controller monitors the level of the
over head tank and automatically switches on the water pump when ever
the level goes below a preset limit. The level of the over head tank is
indicated using 5 leds and the pump is switched of when the over head
tank is filled. The pump is not allowed to start if the water level in
the sump tank is low and also the pump is switched off when the level
inside the sump tank goes low during a pumping cycle. The circuit
diagram of the water level controller is shown below.
The level sensor probes for the overhead
tank are interfaced to the port 2 of the microcontroller through
transistors. Have a look at the sensor probe arrangement for the
overhead tank in Fig1. A positive voltage supply probe goes to the down
bottom of the tank. The probes for sensing 1/4, 1/2, 3/4 and FULL levels
are placed with equal spacing one by one above the bottom positive
probe. Consider the topmost (full level) probe, its other end is
connected to the base of transistor Q4 through resistor R16. Whenever
water rises to the full level current flows into the base of transistor
Q4 which makes it ON and so its collector voltage goes low. The
collector of Q4 is connected to P2.4 and a low voltage at P2.4 means
the over head tank is not FULL. When water level goes below the full
level probe, the base of Q2 becomes open making it OFF. Now its
collector voltage goes high and high at P2.4 means the tank is not full.
The same applies to other sensor probes (3/4, 1/2, 1/4) and the
microprocessor understands the current level by scanning the port pins
P2.4 ,P2.5, P2.6 and P2.7. All these port pin are high (all sensor
probes are open) means the tank is empty.
Port pin P0.5 is used to control the
pump. When ever it is required start pumping, the controller makes P0.5
low which makes transistor Q6 ON which in turn activates the relay K1
that switches the pump. Also the LED d6 glows indicating the motor is
ON. LED D7 is the low sump indicator. When the water level in the sump
tank goes low, the controller makes P0.7 low which makes LED D7 to glow.
The circuit diagram of the water level controller is shown in the
figure below.
Circuit diagram.
Program.
MOV P2,#11111111B // initiates P2 as sensor input
MOV P0,#11111111B // initiates P2 as the output port
MOV A,#00000000B
MAIN:ACALL SMPCK // checks the level of the sump tank
MOV A,P2 // moves the current status of P2 tp A
CJNE A,#11110000B,LABEL1 // checks whether tank is full
SETB P0.1
SETB P0.2
SETB P0.3
SETB P0.4
CLR P0.0 // glows full level LED
SETB P0.5
LABEL1:MOV A,P2
CJNE A,#11111000B,LABEL2 // checks whether tank is 3/4
SETB P0.0
SETB P0.2
SETB P0.3
SETB P0.4
CLR P0.1 // glows 3/4 level LED
LABEL2:MOV A,P2
CJNE A,#11111100B,LABEL3 // checks whether tank is 1/2
SETB P0.0
SETB P0.1
SETB P0.3
SETB P0.4
CLR P0.2 // glows 1/2 level LED
LABEL3:MOV A,P2
CJNE A,#11111110B,LABEL4 // checks whether tank is 1/4
SETB P0.0
SETB P0.1
SETB P0.2
SETB P0.4
CLR P0.3 // glows 1/4 level LED
JB P0.6,LABEL4
CLR P0.5 // switches motor ON
LABEL4:MOV A,P2
CJNE A,#11111111B,MAIN // checks whether tank is empty
SETB P0.0
SETB P0.1
SETB P0.2
SETB P0.3
CLR P0.4 // glows EMPTY LED
JB P0.6,MAIN // checks whether sump is low
CLR P0.5 // switches motor ON
SJMP MAIN
SMPCK:JB P0.6,LABEL5 // checks whether sump is low
SETB P0.7 // extinguishes the sump low indicator LED
SJMP LABEL6
LABEL5:SETB P0.5 // switches the pump OFF
CLR P0.7 // glows sump low indicator LED
LABEL6:RET
END
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