Mohammad Ali Jinnah University, Islamabad.

Automatic Washbasin Tap Controller Project Report

Author: Zaheer ul hauqe

Automatic Washbasin Tap Controller | Zaheer ul hauqe

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Abstract

This is a student report for the Lab Project assigned for Basic Electronics lab, named Automatic

Washbasin Tap Controller. It encloses the working and theory of IC 555 timer, Solenoid Valve,

IRs and IR receivers. The findings, experience and knowledge that we have learned during the

course of fabrication and implementing this project are also shared.

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A thesis submitted in partial fulfilment of the requirements for the degree of Bachelor of Science

in Mechanical Engineering at the Mohammad Ali Jinnah University, Islamabad to Mr. Khurram

Baig regarding the term project named Automatic Washbasin Tap Controller. Names and

Registration no’s of our group are:

Zaheer ul Haque Me113008

Waleed Afzal Me113055

Aoun Abbas Me113074

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TABLE OF CONTENTS Introduction .................................................................................................................................... 4

Theory ............................................................................................................................................. 5

555 Timer IC................................................................................................................................. 5

Monostable mode .................................................................................................................... 5

Astable Mode ........................................................................................................................... 6

Solenoid Valve ............................................................................................................................. 6

IR Receiver ................................................................................................................................... 7

Methodology ................................................................................................................................... 7

Transmitter Circuit ...................................................................................................................... 7

Working .................................................................................................................................... 8

Receiver Circuit ............................................................................................................................ 8

Working .................................................................................................................................... 9

The Heat Exchanger ..................................................................................................................... 9

Working .................................................................................................................................. 10

Conclusion ..................................................................................................................................... 10

Bibiliography ................................................................................................................................. 11

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AUTOMATIC WASHBASIN

TAP CONTROLLER

INTRODUCTION Automatic Washbasin Tap Controller was a circuit given to us as a lab project in order to

strengthen the theoretical concepts and allow us to get a know-how of practical implementation

of the project.

The project could be divided into three parts i.e. the receiver circuit, transmitter circuit and the

heat exchanger. We did not make the heat exchanger due to financial issues as it was taking a

fortune to make o it was dropped.

Both the receiver and transmitter circuits are triggered by 555 timer IC and works on infrared

light. The transmitter sends out infrared light at a certain frequency and the receiver module

receives it to trigger the solenoid valve controlling water flow into and out of the heat exchanger.

For further understanding refer to the block diagram given below.

Transmitter Obstacle Receiver

Valve Open Heat Exchanger

Hot Water

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THEORY Both the receiver and transmitter circuit are using an important component 555 timer IC and

alongside it solenoid valve, receiver infrared sensor which do not come across use normally. We

would proceed with explaining them.

555 Timer IC The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation,

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

a flip-flop element.1

They work in 3 modes: Monostable, Bistable, Astable. We will not be discussing Bistable mode as

it was not used in our project.

MONOSTABLE MODE Monostable means that once the circuit is switched

on it will time once and then stop. In order to start

it again it must be switched on manually a second

time.

Basically In monostable mode the 555 timer

outputs a high pulse, which begins when the trigger

pin is set low (less than 1/3Vcc). The duration of

this pulse is dependent on the values of the

resistors and capacitors connected to it. When the

trigger pin is high, it causes the discharge pin (pin

7) to drain all charge off the capacitor connected to

it. This makes the voltage across the capacitor (and the voltage of pin 6) = 0. When the trigger

pin gets flipped low, the discharge pin is no longer able to drain current, this causes charge to

build up on the capacitor. Once the voltage across the capacitor (the voltage of pin 6) equals 2/3

of the supply voltage, the output of the 555 is driven back low. The output remains low until the

trigger pin is pulsed low again.

1 http://en.wikipedia.org/wiki/555_timer_IC

Figure 1

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ASTABLE MODE Astable means that the 555 can operate repeatedly, it will switch on, then off, then on, then off,

continually.

In astable mode, the output from the 555 timer is a continuous pulse waveform of a specific

frequency that depends on the values of the two resistors connected between input and pin 7

while the other one between pin 7 and pin 6 (Refer to figure 1) and capacitor connected across

pin 6 and ground. Astable mode is closely related to monostable mode. The important difference

is that in astable mode, the trigger pin is connected to the threshold pin; this causes the output

to continuously toggle between the high and low states.

Solenoid Valve A solenoid valve is an electromechanically operated valve. The valve is controlled by an electric

current through a solenoid. Their tasks are to shut off, release, dose, distribute or mix fluids.

They are found in many application areas. Solenoids offer fast and safe switching, high reliability,

long service life, good medium compatibility of the materials used, low control power and

compact design.2

Shown here diagrammatically, the

media controlled by the solenoid valve

enters the valve through the inlet. The

media must flow through the orifice

between inlet and outlet.

The solenoid valve that we intend to

use is normally closed type and the

fluid, before continuing into the outlet

port must go through the orifice which

is closed and opened by the plunger.

The plunger in turn is controlled by a magnetic coil in which the change of magnetic field opens

or closes the plunger. The constant availability of current to the valve is mandatory.

2 http://en.wikipedia.org/wiki/Solenoid_valve

Figure 2

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IR Receiver

An infrared receiver, or IR receiver, is hardware that sends information from an infrared light

emitting device to another device by receiving and decoding signals. In general, the receiver

outputs a code to uniquely identify the infrared signal that it receives. This code (in form of

varying electric pulses of different frequency

and magnitude) is then used in order to

convert signals that it receives into a format

that can be understood by the other device.

It is the part of a device that receives

infrared commands from a remote control.

Because infrared is light, it requires line-of-

sight visibility for the best possible

operation, but can however still be reflected

by items such as glass and walls3.

METHODOLOGY

Transmitter Circuit We started with the transmitter circuit first and checked its logic on breadboard which

fortunately was working. The following circuit was implemented on PCB Wizard3.0 software and

converted into a PCB layout.

The usual method of copying the print on butter paper and then transferring the print on a PCB

sheet was carried out. The ferrous chloride solution did the work and all that was left was the

wanted circuit line. We placed every element in its place and soldered it to strengthen and make

the connection.

We didn’t faced any difficulty in making the transmitter part and everything went by the book.

3 https://www.futureelectronics.com/en/optoelectronics/infrared-receivers.aspx

Figure 3

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WORKING The IC 555 used in this circuit works in

astable mode which has been

thoroughly explained earlier under a

separate heading (Page 6). The IC as

astable vibrator continuously generate

around 38 kHz frequency which is fed

as output to transistor T1, which drives

the IR LED. Its transmission wavelength

of 900 to 1100 nm lies in the peak

receptivity range of TSOP1738 receiver

module.

The potentiometer used in the circuit

was used to vary the frequency of the

output light.

Receiver Circuit The 555 IC used as

monostable timer

(Discussed earlier on

page 5) was

implemented in this

part of the project. The

PCB sheet was

fabricated in the same

fashion as transmitter

circuit.

This relatively harder

part tested our

concepts of the course

and we had a hard time constructing it. The problems that we faced was in experience being an

alien to the field and also that the IRs available in the market weren’t as the circuit demands. The

Figure 4

Figure 5

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requirement was that IR should send a high pulse in idle time and while sensing an obstruction

its output should go low momentarily but the available IRs were doing just the opposite.

The solution that we came upon, after several hit and trial attempts, was to use a NOT gate and

invert the output of the IR which was to be fed to the IC.

WORKING The rays falling on the IR causes it to continuously give out a high pulse but as soon as the

obstruction (hand) is detected the output goes low the very instant. This low pulse is fed to the

IC via a timing capacitor which triggers the monostable mode for up to 11 seconds. We used a

different capacitor (10 µF) than the mentioned one which ha minutely affected the timing of the

circuit. Now instead of 11 seconds which was intended, the circuit remains on for 12.2 seconds.

The output of the 555 is fed to the relay via a transistor which is in normally closed state. The

diode connected to it in parallel prevents the backward flow of current from Vcc. Upon receiving

the signal from transistor, the relay switches on and turns on current towards the valve.

The Heat Exchanger Although we did not fabricated this part as the cost was too high but we still managed to calculate

its power and other parameters. The exchanger was supposed to be small 2 liter container which

can hardly be considered a tank.

The heating mechanism was intended to be of electric type as it is easier to work upon.

Cold Water In

Heating Element

Hot Water Out

Hot Water Rising

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WORKING The Heating element which would be triggered by a flow sensor fitted on the pipe assuring the

flow of water and eliminating the risk of dry heating that may occur due to any reason was

intended to be electrical. I made the calculations based on the flow rate of my dorm’s washrooms

water supply which experimentally came out to be 0.1 liter per second. As 𝜌 = 𝑚 𝑉⁄ and ρ being

1000 kg/m3 for water the mass rate came out to be 1 kilogram per second. Now from

𝑄 = 𝑚𝑐∆𝑇

Where Q is heat energy in joules, m, the mass of water, c being the specific heat of water and

∆𝑇 the desired temperature difference, I calculated my heat element to be of 2 KW. The

calculations are given below.

𝑄 = 𝑚𝑐∆𝑇

𝑄 = 1 𝑘𝑔 × 4186 𝑗

𝑘𝑔. °𝐶× 50 °𝐶

𝑄 = 209300 𝑗

Or

𝑄 = 209 𝐾𝑗

Shuffling the units you will get 2 KWh which is the optimum power element required to create a

positive difference of 50°C in temperature of 0.1 liter of water every second.

CONCLUSION This project was really interesting and enabled us to work outside our line of work. Practical

implementation of textbook concepts is very different dimension which is yet to be mastered

by us. It is these projects that helps us in doing so. This project removed the stereotyped idea

that, we the students of Mechanical engineering shouldn’t be studying electronics.

The world cannot be divided into different fields and to achieve success all the laws of physics

and the fields of engineering must work in a harmony so that us and our fellow humans can live

a better life and an elevated living standard.

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BIBILIOGRAPHY http://www.technologystudent.com/elec1/5554.htm

http://www.instructables.com/id/555-Timer/step2/555-Timer-Monostable-Mode/

http://www.allaboutcircuits.com/vol_6/chpt_8/4.html

http://www.dummies.com/how-to/content/electronics-components-how-the-555-

timer-chip-work.html

http://www.doctronics.co.uk/555.htm

http://www.technologystudent.com/elec1/5555.htm

http://www.instructables.com/id/555-Timer/step5/555-Timer-Astable-Mode/

http://maritime.org/doc/fleetsub/refrig/img/fig7-11.jpg

http://www.answers.com/topic/infrared-receiver

http://media3.rsdelivers.cataloguesolutions.com/LargeProductImages/RF286142-01.jpg

http://en.wikipedia.org/wiki/Solenoid_valve

http://www.solenoid-valve-info.com/solenoid-valve-basics.html

http://www.ask.com/question/how-does-a-solenoid-valve-work

https://www.futureelectronics.com/en/optoelectronics/infrared-receivers.aspx