KE36103 Instrumentation and Measurement

Assignment Session 2014 / 2015

Title of reportLEDs Christmas Light

Group Member1. Tony Kiing Teck Hua BK12110371

2. Mohd Haizal bin Adnan BK121102033. Nurul Anis Ahmad BK12110284

4. Norazreena Bussera BK12110251

ExaminerDR. Ahmad Mukifza Harun

Date of Submission: 31 / 12 / 2014

MarksDemonstration : ______/10 marks

Q & A: ______/5 marksReport : ______/7 marks

Total : ______/22 marks

1.0Introduction

Christmas is known as the carnival of lights and every person decorates

its house, shopping complex, and garden with multicolored lights which we

normally purchase from the bazaar. Hence, the idea of creating the LEDs

Christmas Light is generated. This idea is suitable for placed the Christmas

tree in garden and so on. The users no need to switch on or off in manually

way. It can be automatically turned on the LEDs of Christmas tree when the

sensor not detects light. When the sensor detects light in night time, the LEDs

of Christmas tree will switch off automatically. The main controlling circuit

consists of the sensor and an indicator. For this particular design, the LDR is

used as a sensor whereas the LEDs and buzzer are used as the indicator. In

general, this LEDs Christmas Light operate when the sensor, light dependent

resistor (LDR) is not detects the light during night time the circuit will

operated. When the sensor, light dependent resistor (LDR) detects light the

circuit will not operated.

2.0Objectives

To apply the knowledge learned throughout the course, Measurements

and Instrumentation in designing a circuit of relevance.

To design a LED Christmas light circuit by using LDR

3.0 Block Diagram

4.0Functional Description

IC TC4093BP The TC4093B is a quad 2-input NAND gate having

Schmitt trigger function for all the input terminals.

Since the circuit threshold voltage varies with rising

time and falling time of the input waveform (VP and

VN), this gate can be used for a wide variety of

applications to line receivers, waveform shaping,

astable multivibrators, monosatable multivibrators in

addtion to regular NAND gates.

Light Dependent

Resistor (LDR)

A device whose resistivity is a function of the incident

electromagnetic radiation. Hence, they are light

sensitive devices. They are also called as photo

conductors, photo conductive cells or simply

photocells. They are made up

of semiconductor materials having high resistance.

BC547 An NPN bi-polar junction transistor commonly used to

amplify current. A small current at its base controls a

larger current at collector & emitter terminals.

BC547 is mainly used for amplification and switching

purposes

Variable Resistor It is applied in an electronic circuit for adjusting circuit

resistance to control voltage or current of that circuit

or part of that circuit. The electrical resistance is

varied by sliding a wiper contact along a resistance

track. Sometimes the resistance is adjusted at preset

value as required at the time of circuit building by

adjusting screw attached to it and sometimes

resistance can be adjusted as when required by

controlling knob connected to it. 

Resistor A passive two-terminal electrical component that

implement electrical resistance as a circuit element.

Resistors act to reduce current flow and at the same

time act to lower voltage levels within circuits. In

electronic circuits resistors are used to limit current

flow, to adjust signal levels, bias active elements,

terminate transmission lines among other uses.

Capacitor Used to store an electrical charge. A capacitor may be

used with a resistor to produce a timer. Sometimes

capacitors are used to smooth a current in a circuit as

they can prevent false triggering of other components.

When power is supplied to the circuit that includes a

capacitor – the capacitor charges up. When power is

turned off the capacitor discharges its electrical charge

slowly.

Light Emitting Diode

(LED)

 It consists of semiconductor material and produces

different colors of light as its output.

5.0 The parts, materials and cost expenses.

No Quantity Items Price per unit (Rm)

Total price(Rm)

01 1 IC-TC4093BP 3.50 3.5002 2 Transistor- BC547B SI-N 0.90 1.8003 5 1/4W Carbon Film Resistor 0.30 1.5004 1 LDR (CDS) Photo Resistor 1.80 1.8005 1 100k 1/16W Trimmer 1.40 1.4006 1 22 uF 16vdc Electrolytic

Caps0.50 0.50

07 2 Red (5mm) LEDs 0.50 1.0008 2 Green (5mm) LEDs 0.50 1.0009 2 Orange (5mm) LEDs 0.50 1.0010 9 meter Tinned Copper Wire (thin) 0.60 5.4011 1 Strip Board (64 mm x 145

mm)3.50 3.50

12 1 14 pins IC Socket 1.00 1.0013 1 Christmas Tree 6.90 6.9014 1 9V battery holder 1.50 1.5015. 1 Battery 9V 4.50 4.5016 1 Music element(christmas

cards)3.90 3.90

17 1 Crystal white LEDs 1.00 1.00Total 41.20

6.0 Circuit Analysis

This circuit is mainly made up of TC4093BP IC. It is a quad 2-input NAND gate

having Schmitt trigger function for all the input terminals. Since the circuit

threshold voltage varies with rising time and falling time of the input

waveform (VP and VN), this gate can be used for a wide variety of

applications to line receivers, waveform shaping, astable multivibrators,

monosatable multivibrators, etc. All LEDs are employed in this circuit with a

sensor or transducer along with some other components like transistor, diode

and resistors. The supply 3V to 18V is the voltage DC working range of these

IC.

Out of 14 pin package pin number 14 and 7 is used for connecting battery or

power supply. Pin 7 is attached with the negative terminal while pin 14 is

attached to the power supply. As we have already familiar that it is consist of

four gates we named them as NI1, NI2, NI3 and NI4.In the first gate i.e. NI1

pin 1 and 2 is for the input purpose while pin 3 is for the output. You can find

in the circuit diagram shown below. When the entire input terminal is in high

state the output moves toward the low state, or else we will obtain high

output. This can be employed in the truth table drawn below.

This can be employed in the truth table drawn below.

Figure 1.1 TC4093BP IC Pin Diagram and Truth Table.

This whole circuit is parted into two parts first one is for the sensor section

and the second one is for the LED flasher section and music section. The light

sensing part of the circuit is constructed using LDR along with two transistors

C547B namely T1 and T2. During the day time light resistance of LDR is low

minimum at less than 1.0 MΩ, the current flow into B part (Base in CBE

transistor) is which in turn make the transistor T1 into transmission due to

this T2 transistor voltage goes to the low state and left over in the cut off

state. That is why during the day time LED attached at the output point will

not shine and no music will be played. While at the time of night when no

light is present LDR, LDR reaches to high resistance which is more than 1 MΩ

, as a result of it conduction of T1 stops and T2 begins its conduction same as

the T1 before. Due to its LED attached at the output starts glowing and the

music starts playing.

At this instant, LED flashing circuit is constructed around IC TC4093BP which

is functioning in oscillator mode while the music will be played continuously.

With the assistance of resistor R2 of 100 kΩ and capacitor C1 22µF oscillation

part is being created. So when the charging of the capacitor C1 reaches to

the half of the power supply which is 4.5v, output from the pin3 IC1 move

lower and the capacitor C1 discharges. This is because when capacitor is

charging to 4.5V the pin1 and 2 is high. Then the pin3 will become low. After

capacitor discharge, the pin1 and 2 become low then the pin3, 4 and 5 will

become high and the capacitor C1 again charges. So the above cycle keeps

on going after power is supplied in the circuit. This is called as Half-Wave

Rectifier with smoothing capacitor.

R provides control to the rate of charging and discharging, without resistance,

the capacitor will charge &/or discharge instantaneously, R limits the current,

thereby allowing the charging and discharging to happen gradually, governed

by:

Vch=V(1-e^(-t/τ))

Vdch=V(e^(-t/τ))

Where V=system/total/ supply voltage

t= time instance under consideration

τ=Time Constant=R*C

Vch= Capacitor Voltage at time t during charging

Vdch=Capacitor Voltage at time t during discharging

For time charging,

V=9.0 V, t= time instance , τ=R*C = (100k x 22µ) = 2.2 s

Vch= 9.0 / 2 = 4.5 V

Substitute the values into equation Vch=V(1-e^(-t/τ))

We get t = 1.52 s

Note that the time charging is equal to time discharging as calculate from the

formula given Vdch=V(e^(-t/τ)).

The 3 LED of the first line is connected to pin4 and second line is connected

to pin10 from power supply directly. When the capacitor is discharging, the

current will flow to pin3 as well as 5 and 6 are 0(low). This 0 0 in input (pin5

and 6) cause the output pin4 signal is 1, the first line will not flashing due the

current signal are in interference (positive polarity both and not connected to

the ground) and the second line is flashing because it has 1 1 input in pin9

and 8 (because pin4 is 1 and pin4, 9 and 8 are connected together) and the

output is 0 in pin 10 cause the current can flow to the ground (different

polarity of current signal). When capacitor is charging, the output of pin 4 is 0

because the input is 1 1 from pin5 and 6 as the current is flow to the

capacitor to charge it, this time the first line flashing while the second line is

not due to the input of pin9 and 8 is 0 0 due to the current flow into pin4 and

the output is 1 in pin10.

From the first line and second line, the node voltage is 8V and the resistor is

330Ω. The node voltage only has 8V because transistor has dissipated 1V.

The LED in series has same voltage value which is 1.8V each same with the

second line LED. Also, the current flow to the LED normally is 0.01A. Thus, the

voltage flows to the IC input line is 8V-3(1.8V) = 2.6V. By applying the Ohm’s

law, V=IR. The resistor value that we used is 2.6/ 0.01 = 260ohm. Due to the

reason that we cannot get 260ohm resistor in market so 330ohm resistor is

chosen to use in this circuit so the current flow to the LED is around 0.08A. At

the line of the music, the resistor is 560ohm before its going to parallel

between the white LED and the music element. The white LED needs 3V

supply so the power supply to music element also is 3V. White LED required

0.008A to light it up so the resistor value for the resistor before LED is (8V-

3V)/0.008 =625ohm. Since music element need only some current to operate

it so we put a resistor which have the resistor value that are lower than

625ohm so that there have some current can flow through the music

element. 560ohm resistor is used in the circuit.

By altering the value of the resistor R2 as well as capacitor C1, you can

enlarge or reduce the rate of the LED flashing. Suppose you want to increase

the flashing rate of light then just reduce the value of C2 capacitor and for

reducing the rate just increase the value of the capacitor. And for maintaining

the sensitivity of the LDR in the circuit all you need to use a variable resistor.

7.0 Discussions

In simpler way, the LEDs in this circuit will flashing and the music will be

turned on in the absence of the light. When the LDR detects light in the

daylight, the resistance of its will be low and caused the current flows in the

transistor T1 circuit and transistor T2 will be cut-off. The LEDs will not be

flashing and the music is off in this state. In the absence of light during night

time, the resistance of the LDR will goes high up, caused the current to flow

in the transistor T2, and transistor T1 will be cut-off. Thus, the LEDs will be

flashing and the music is on in resulting of the absence of light. The variable

resistance, VR1, can be varied for the light intensity of the LEDs. The flashing

LEDs and the musics will be a good decorations for the Christmas tree in this

holiday season. Table below will summarize the operation of the design:

Light Resistance of LDR LEDs Music

Presence Low Off Off

Absence High On On

Table: Operations of the Christmas Tree

8.0 Conclusions

The objective of this project is achieved as the mini project is a success. The

Christmas tree works pretty well on the breadboard connection and also on

the prototype. This design is within budget located and can be said as a low

cost project. All the component works as all the input element, the signal and

conditioning element and also the output element producing the desired

outcomes for the design.

9.0 Reference

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

2. http://electrical4u.com/

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