07 Enr Ranjan Tarafdar

7/28/2019 07 Enr Ranjan Tarafdar

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07-ENR-RANJAN TARAFDAR

WATER LEVEL CONTROLLER USING 555 TIMER IC

Ranjan Tarafdar, B-Tech, 3rd year student, Guru Nanak Institute of Technology, Sodepur, Kolkata-

700114Madhulina Sur, B-Tech, 3rd year student, Guru Nanak Institute of Technology

Dibyendu Sur, Life Member FOSET, Member IEEE, Assistant Professor, Guru Nanak Institute ofTechnology

Abstract

Automatic water level controller circuit is a simple engineering project. It can

automatically switch ON and OFF the domestic water pump set depending on the tank water

level. You can implement this motor driver circuit at your home or college using less costly

components. The approximated cost of the project is very less. The main advantage of this

water level controller circuit is that it automatically controls the water pump without any user

interaction.

The heart pump controller circuit is a NE 555 IC; here we have manipulated the

flip flop inside the 555 timer IC. Our project consists of three water level sensors, one fixed

at the top and other at the bottom. Working of this circuit is almost similar to a Bi stable

mutlivibrator. Simulation of this circuit is also given below.

Introduction

People generally switch on the pump when their taps go dry and switch off the pump

when the overhead tank starts overflowing. This results in the unnecessary wastage and

sometimes non-availability of water in the case of emergency.

The circuit that we are using makes this system automatic, i.e. it switches on the pumpwhen the water level in the overhead tank goes low and switches it off as soon as the water

level reaches a pre-determined level. It also prevents dry run of the pump in case the level

in the tank goes below the suction level.

Water Level Controller employs a simple mechanism to detect and maintain the water level

in a tank or any other container by switching it on/off the motor automatically when needed.

The level sensing is done by three sensors which are placed at different levels on the tank

walls.

The three sensors are placed as following:Sensor C- At the bottom of the tank.
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SensorB- A little above of sensor 1.

Sensor A-At the top of the tank.

The three sensors are maintaining the water level in the tank by triggering & retriggering the

timer IC. Here the timer IC is acting in monostable mode or one-shot mode. Sensor C carriesthe +Vcc supply thus when the water level falls below sensor B the timer IC is triggered &

the pump is energized through a relay & transistor. Now when the water reaches the topmost

level & touches sensor A it retriggers the timer IC once again & and the pump is switched off

automatically.

Hence this water level controller is one of the cheapest & simplest devices which prevents

wastage of both electricity & water.

Components Required

1. Power supply (12v)

2. NE 555 timer IC

3. Resistors (100x2, 10k,1k)

4. Relay (12V, 30A)

5. SL 100 transistor

6. 1N4007 Diode

Power Supply For This circuit

Fig .1: Power Supply For The Circuit
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A classic 12V regulated DC supply based on 7812 is shown. This circuit works on

12 V DC supply, we need a step down transformer of 12 V 300mA.It converts input 230 AC

voltage to 12V AC as an output. Then this AC voltage is rectified using a rectification circuit

with 4 diodes connected in a bridge form. The output after the diode is 12V DC which is

rectified using rectifier 7812. This rectified output of 12V DC is used in the circuit.

Pin Configuration of 555 timer IC

Fig. 2 : Pin Configuration of 555 Timer IC

The 555 timer IC is an integrated

circuit (chip) used in a variety oftimer,

pulse generation,

andoscillator applications. The 555 can be used to provide time delays, as an oscillator, and

as a flip-flop element. The NE555 parts were commercial temperature range, 0 C to +70 C,

and the SE555 part number designated the military temperature range, 55 C to +125 C.

These were available in both high-reliability metal can (T package) and inexpensive epoxy

plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V,

and SE555T.

Monostable mode of 555 Timer IC

In our level controller timer IC works on monostable mode. In this mode, the 555

functions as a "one-shot" pulse generator.
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Fig. 3 : Response in Monostable mode Fig. 4: Internal circuit 555 Timer

The pulse begins when the 555 timer receives a signal at the trigger input that falls below a

third of the voltage supply. The width of the output pulse is determined by the time constant

of an RC network, which consists of a capacitor(C) and a resistor(R). The output pulse ends

when the voltage on the capacitor equals 2/3 of the supply voltage. The output pulse width

can be lengthened or shortened to the need of the specific application by adjusting the values

of R and C.

The output pulse width of time t, which is the time it takes to charge C to 2/3 of the supply

voltage, is given by

where t is in seconds, R is inohms and C is in farads.
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Fig.5: Circuit Diagram

Working of Automatic water tank level controller

We know the property of 555 timer IC, i.e. its output goes HIGH when voltage at the

second pin(trigger pin) is less than 1/3 Vcc.

Also we can reset back the IC by applying a LOW voltage at the 4th pin (Reset pin).

In this project 3 wires are dipped in water tank. Let us define two water levels-

Bottom (L) level and Top (H)

level. One of the wire or probe is

from Vcc, which can be called as

middle level (M).

Fig.6: Position of three sensors in timer

555

The probe from bottom level is connected to the trigger (2nd) pin of 555 IC. So the

voltage at 2nd pin is Vcc when it is covered by water.


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When water level goes down, the 2nd pin gets disconnected(untouched) from water

i.e. voltage at the trigger pin becomes less than Vcc. Then the output of 555 becomes

high.

The output of 555 is fed to a SL 100 transistor, it energizes the relay coil and the

water pump set is turned ON.

Fig.7: SL 100 transistor

While the water level rises, the top level probe is

covered by water and the transistor becomes ON. Its

collector voltage goes to Vce(sat) =0.2V.

The low voltage at the 4th pin resets the IC. So the output of 555 becomes 0V. Hence

the motor will turn OFF automatically.

For practical implementation, you must use a relay. Rating of relay is chosen

according to the load (Motor). 32 Ampere relay is best suited for domestic

applications.

Probe/Sensor arrangement diagram


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Fig.8: Probe/Sensor arrangement diagram

The probes can be arranged as shown in the diagram above. Insulated

Aluminium wires can be used as the probes. The probes can be binded on a plastic rod and

should be erected vertically inside the tank. The length of the probes wires and the supporting

plastic rod must be chosen according to the depth of the tank. Since DC is used in the level

sensing section electrolysis will occur in the probes and so the probes require small

maintenances in 6 or 7 month intervals.

Conclusion

Thus by using this simple arrangement we can save wastage of water and

electricity. It is very important for us to control the use of natural source of energy. By

using this circuit we can solve our purpose very easily.

Reference

www.ebookbrowse.com

www.electronicsforyou.com

www.digitek.in

www.sridigitek.com
http://www.electronicsforyou.com/http://www.digitek.in/http://www.electronicsforyou.com/http://www.digitek.in/

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07 Enr Ranjan Tarafdar