Automatic water pump on/off

School Project : Automatic Water pump On/off

It’s a device which detect the level of water on the water tank . If the level is low , it will automatically start the water pump and if the level is high it will stop the water pump.

 To build this  the property of water to conduct electricity is used

 

                                                                                                                                     

In the above figure, the red wire is dipped to the button of tank. The red wire is directly connected to the battery  through resistor. So there is small amount of electricity in water.

There are two sensing wire , Wire B is used to sense the low level of water. Wire A sense the high level of water. When the water level is below the B , the water pump should automatically turned On . It will remain On until the water level touches the Wire A. And the water pump start once again when water level goes below wire B.

 

 

To make this we need to understand the concept of latch.

Latch is basically a single bit storing circuit made from transistors. 

                                                                                                            

                                                         Figure: Latch circuit using NAND Gate

                                                                                   

X	Y	Output
0	0	1
0	1	1
1	0	1
1	1	0

 

 

 

 

 

 Figure: Truth table of NAND GATE

 Let’s understand the working of NAND Gate.

·        When the A= 0 and B=1,

                                             The output(Q)  is 0.

 

·        When the A=1 and B=0,

                                            The output(Q) is 1.

 

·        When the A=1 and B=1,

                                            This condition is called memory where output(Q) is the previous output.

·        When the A=0 and B=0,

                                            This is invalid state.

 

Now to make our project we have to add a inverter to the input A. The water pump is connected in output .

 

                                                    

                                                                   

                                                    Figure: Circuit of automatic water pump On/Off

 

Lets understand its working Principle,

·        When water level is below B,

                                                     It means B=0 ( current cannot reach to wire B from water ) and A=1 . It means output will be 1. So water pump  is On.

 

·        When water level touches B,

                                                     It means B=1 and A=1, so this is the case of memory so output will maintain its pervious state which is ON.

 

·        When water level touches A,

                                                      It means B=1, A=0 ( as inverter circuit is connected to A) so output is 0. The motor is Off.

 

·        When water level is below A and above B,

                                                                             It means B=1, A=0 so the outout will be 0. The mtor remain off.

 

The motor will remain off until the water level goes below Wire B. When the water level is comes below B then motor will start again.

 

Here is the picture from proteus simulation of the project. The circuit is built using NPN BC574 Transistor.