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DAE 21402 MINI PROJECT DUE DATE: WEEK 13

Overview

Each group is to build and make measurements on a simple measurement system as in Table 1. The group is to do a laboratory demonstration on the results obtained.

TABLE 1

GROUP / Circuit / GROUP / Circuit / GROUP / Circuit / GROUP / Circuit
1 / 1 / 6 / 2 / 11 / 3 / 16 / 4
2 / 2 / 7 / 3 / 12 / 4 / 17 / 1
3 / 3 / 8 / 4 / 13 / 1 / 18 / 2
4 / 4 / 9 / 1 / 14 / 2 / 19 / 3
5 / 1 / 10 / 2 / 15 / 3 / 20 / 4

Circuit 1: Fire Alarm Using Thermistor

Circuit 2: Air Flow Detector Circuit

Circuit 3: Water Level Alarm Circuit

Circuit 4: A Simple Light Activated Switch

Learning Outcomes:

With the successful implementation of this mini project, the students are expected to use the knowledge and skills learned to:

  1. Translate the given circuit to real elements connection using appropriate software/ tools.
  2. Conduct technical presentation effectively.
  3. Write technical report effectively.
  4. Work in groups efficiently.

Guidelines:

  1. Student will work in a group of 3 members..
  2. Plagiarism and ‘sleeping-partner’ will not be permitted. All students should work effectively in their own team.
  3. Both or more parties involved in the plagiarizing case will receive zero marks.
  4. All documentation for this mini project should be typed properly. Hand-written documentation will not be graded.
  5. All report must be written in ENGLISH using passive sentence structure and not active structures to show that the instructions have been carried out.

TASKS

Each group is required to do the following:

  1. Build a voltage regulator circuit using IC regulator of the 78XX series for the relevant circuit.
  2. Perform the real circuit test on test board (Breadboard). Record your results.
  3. Develop the PCB board for the circuit using appropriate software.
  4. Solder the circuit elements on the PCB board and perform the final test. Compare the results obtained with results from Task No. 2.
  5. Design the proper casing/housing for the circuit board.
  6. Built ONE prototype of this mini project.

Note:Creativity, tidiness and safety measures must be considered in these tasks.

EVALUATION

LAB DEMONSTRATION (50%)

  • 80% is Hardware meeting specifications
  • 20% is Neatness and correct use of equipment and components.

Project Report (50%)

1. INTRODUCTION

It is a paragraph or series of paragraphs that introduce the reader to the subject. The introduction presents basic background material, the history of the problem, or introduces most of the major references any. The best approach is to write an introductory paragraph that contains key sentences outlining the subjects to be discussed. Follow the first paragraph by expanding on each of these key subjects alreadyintroduced. In the format recommended here, theory and mathematical constructs are generallynot part of the introduction. The introduction of an engineering paper should be less than twopages long. Illustrations are seldom used in an introduction.

2. THEORY

This section explains the theory behind the work and is the place for the mathematics. This section contains the general equations that describe the system under study.

The presentation of general theory early in the report allows the writer to refer to these basic ideas and equations later in the paper without restating the facts each time they are used. Illustrations should be

limited to graphs or other basic diagrams.

3. METHODS

In this part of the report specific explanations for the apparatus, instruments, calibrations, etc., are discussed. The basic idea here is that these procedures are not obvious and deserve some explanation beyond what might be outlined in other parts of the report. Diagrams of the apparatus should appear in this part of the report.

4. RESULTS / DISCUSSION

A good report presents some discussion of the results. The basic findings of the study or experiment should be outlined in detail with the appropriate graphs and charts. Equations can also be included in this section but these are not the general theory that is unique to the theory section of the report. Mathematics when presented in this part of a report should be specific to the result being discussed with as many predefined variables as possible.

5. CONCLUSIONS

The conclusions should be a specific and factual summary of the report.

6. REFERENCES

A list or bibliography listing all the sources for the report. The student should conform to the IEEE standard. Find out by looking at the end of any paper in any IEEE publication.

Good Luck!

Circuit 1: Fire Alarm Using Thermistor

Many fire alarm circuit is published in different website. But, here in this website is a simple and inexpensive project of fire alarm using thermistor. where thermistor is used astemperaturesensor of fire alarm.Working principle of thermistor is same as LDR (change their resistance with change in heat where LDR change their resistance with change in light fall on it).

Circuit Description of fire alarm using thermistor

The whole circuit of fire alarm using thermistor is build and fabricated around thermistor (TH1) and timer IC (IC1) with its driver transistor. The timer IC (IC1) used in this circuit is as astable multivibrator oscillator used to oscillate in audio frequency band. The two transistor T1and T2used to drive the timer IC (IC1). The output from pin 3 of IC1is fed to loudspeaker through transistor T3to generate sound. The value of resistor (R5and R6) and capacitor (C2) determines the frequency of IC2.

The low resistance path of extend positive voltage to the base of transistor is provided when the thermistor TH1become hot. Further collector of transistor T1is connected to base of transistor T2provides positive voltage to reset pin 4 of IC1for reset. Fire alarm using thermistor circuit works on wide range of input power supply voltage i.e. 6v to 12V.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

VR1= 10 Kohms Variable Resistor for changing the sensitivity of the circuit.

1

R3, R7, R8= 470 Ω

R2= 33 K Ω

R4= 560 Ω

R5= 47 KΩ

R6= 2.2 KΩ

Capacitors

C1= 10 µF/16V

C2= 0.04 µF

C3= 0.01 µF

Semiconductors

IC1= NE555 (timer IC)

T1= BC548

T2= BC558

1

T3= SL100B or any Medium power general purpose NPN transistor like: 2N4922 , 2N4921,2N4238, FCX1053A

D1= 1N4001

Miscellaneous

TH1= Thermistor 10 KΩ

LS1= 8 Ω, 1W speaker

Measurements required (Circuit 1):

  1. Output from Voltage regulator circuit: Volts
  2. Thermistor at room temperature
  • Base of transistor T1: Volts
  • Pin 4 of IC1 (555 timer): Volts
  • Waveform at Pin 3 of IC1 (555 timer):

  • Loudspeaker: ON/OFF
  1. Thermistor HOT
  • Base of transistor T1: Volts
  • Pin 4 of IC1 (555 timer): Volts
  • Waveform at Pin 3 of IC1 (555 timer):
  • Loudspeaker: ON/OFF

Circuit 2: Air Flow Detector Circuit

Description.

This circuit can give a visual indication of the rate of air flow. It can be also used to check whether there is air flow in a given space.

The filament of a incandescent bulb is the sensing part of the circuit.When there is no air flow the resistance of the filament will be low. When there is air flow the resistance drops, because the moving air will remove some of the heat generated in the filament. This variations in the resistance will produce variation of voltage across the filament. These variations will be picked up by the opamp (LM339) and the brightness of the LED at its output will be varied proportionally to the airflow.

Circuit diagram with Parts list.

Notes.

  • The filament L1 can be made by removing the glass of a 40W incandescent bulb.
  • The circuit can be powered from a 12 V DC power supply.

Measurements required (Circuit 2):

  1. Output from Voltage regulator circuit: Volts
  2. No Air Flow
  • Pin 5 of IC2 (LM339): Volts
  • Pin 4 of IC2 (LM339): Volts
  • Pin 2 of IC2 (LM339): Volts
  • LED: ON/OFF
  1. With Air Flow
  • Pin 5 of IC2 (LM339): Volts
  • Pin 4 of IC2 (LM339): Volts
  • Pin 2 of IC2 (LM339): Volts
  • LED: ON/OFF

Circuit 3: Water Level Alarm Circuit

Description.

Here is a simple water level alarm circuit using 555 timer that will produce an audible alarm when the water level reaches a preset level.The circuit can be powered of a 3V battery and is very handy to use.

The circuit is based on an astable multivibrator wired around IC1 (NE 555).The operating frequency of the astable multivibrator here will depend on capacitor C1, resistances R1,R2 and the resistance across the probes A&B. When there is no water up to the probes, they will be open and so the multivibrator will not produce oscillations and the buzzer will not beep. When there is water up to the level of probes, some current will pass through the water, the circuit will be closed to some extend, and the IC will start producing oscillations in a frequency proportional to the value of C1,R1,R2 and the resistance of water across the probes. The buzzer will beep to indicate the presence of water up to the level of the sensing probes.

Circuit diagram with Parts list.

Notes.

  • The circuit can be powered of a 3V battery.
  • Assemble the circuit on a good quality PCB or common board.
  • The probes can be made of two insulated copper Aluminum wires.
  • Place the probes at the position where you have to sense the level.

Measurements required (Circuit 3):

  1. Output from Voltage regulator circuit: Volts
  2. No water detected between the probes A&B
  • VAB: Volts
  • Waveform at Pin 3 of IC1 (555 timer):
  • Buzzer: ON/OFF
  1. Water detected between the probes A&B
  • VAB: Volts
  • Waveform at Pin 3 of IC1 (555 timer):
  • Buzzer: ON/OFF

Circuit 4: A Simple Light Activated Switch

Description.

This is the circuit diagram of a light activated switch based on National Semiconductors comparator IC LM 311 and a LDR.

The circuit is based on a voltage comparator circuit wired around IC 1.The non inverting in put of IC1 is given with a reference voltage of 6V using resistors R3 and R4. The input to the inverting input will be the voltage across the LDR that is light dependent. At darkness the resistance of the LDR will be high and so do the voltage across it. At this condition the voltage at the inverting input will be higher than the reference at non inverting pin and the output of the comparator will be low(~o V). When the LDR is illuminated, its resistance drops and so do the voltage across it. Now the voltage at inverting input will be lower than that at non inverting input and the output of the comparator goes high (~12 V). This makes transistor Q1 on and it drives the relay. As a result we get a relay switching according to the intensity of the light falling on the LDR.

Light Activated Switch Circuit Diagram

Notes.

  • Adjust POT R1 to set the desired light intensity for switching the relay. For this illuminate the LDR with the desire intensity light. The relay will be either on or off. Adjust POT R1 slowly so that the state of the relay changes. That’s it. Now the circuit is set for the given intensity of light.
  • Assemble the circuit on a good quality PCB.
  • The pin 5&6 (Balance & Balance/Strobe) of IC LM311 are shorted to minimize the chance of oscillations.
  • The pin out of LM311 is also given together with the circuit diagram.

Measurements required (Circuit 4):

  1. Output from Voltage regulator circuit: Volts
  2. No Light on LDR
  • Pin 2 of IC1 (LM311): Volts
  • Pin 3 of IC1 (LM311): Volts
  • Pin 7 of IC1 (LM311): Volts
  • LED: ON/OFF
  • Relay: ON/OFF
  1. LDR Illuminated
  • Pin 2 of IC1 (LM311): Volts
  • Pin 3 of IC1 (LM311): Volts
  • Pin 7 of IC1 (LM311): Volts
  • LED: ON/OFF
  • Relay: ON/OFF