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Unit 2: ANALOG ELECTRONICSTime: 38 Hours

DescriptionIn this unit students perform a series of circuit construction activities to develop an understanding of analog components and circuit design. Students develop practical skills in troubleshooting and continue to demonstrate safe work practices in an electronic shop environment. Students learn the basis for electronic signal production and manipulation, particularly in the area of sound amplification and reproduction. Subsequently, students examine the procedures in creating printed circuit boards and the manufacturing processes in communication electronics.

ExpectationsThe following expectations are covered in this unit’s activities :

Strand Overall Specific

Theory and Foundation TVF.02.1W TVF.03.1W

TF2.05.1W TF2.07.1WTF2.08.1WTF2.10.1W TF2.12.1W

TF2.13.1W TF2.14.1W TF3.01.1W TF3.02.1W TF3.01.1WTF3.02.1W

Skills and Processes SPV.01.1WSPV.02.1WSPV.04.1W

SP1.01.1W SP1.02.1W SP1.03.1W SP2.01.1W SP2.02.1W SP2.04.1W


Impact and Consequences IC2.01.1W IC2.02.1WSee Appendix E for full description of TGJ3E expectations

HRDC NOC Specialized SkillsThe activities in this unit are designed for occupations that require troubleshooting electrical signals, designing and building analog circuits, writing test reports, reading schematics and using testing equipment. Though most careers identified by HRDC as related to electronics can benefit from the skills and knowledge addressed in this unit, the following career categories are directly related to the activities in this unit:

2133 Electrical and Electronics Engineers2241 Electrical and Electronics Engineering Technologists and Technicians 2242 Electronic Service Technicians (Household and Business Equipment) 2243 Industrial Instrument Technicians and Mechanics 2244 Aircraft Instrument, Electrical and Avionics Mechanics, Technicians and Inspectors 7245 Telecommunications Line and Cable Workers 7246 Telecommunications Installation and Repair Workers 7247 Cable Television Service and Maintenance Technicians 7332 Electric Appliance Servicers and Repairers 9483 Electronics Assemblers, Fabricators, Inspectors and Testers 9484 Assemblers and Inspectors, Electrical Appliance, Apparatus and Equipment

Manufacturing

Unit 2 Overview - 23 - TGJ3E (Microelectronics)

ActivitiesThe activities in this unit are designed to be sequential to give the student progressive challenges in circuit design, build and testing. Students learn the theory of electronics and analog circuitry through hands-on projects that are based on signal processing, measuring and calculation electrical parameters, and use of test instrumentation. By concentrating on the audio and visual portion of the electromagnetic spectrum, these projects are related to media productions in communications technology, and will give students the basic principles of telecommunications and photonics in later projects.

Activity Activity Title Time (minutes)

1 The 555 Timer 4802 Audio Electronics: Signal Processing 6003 Project Loudspeaker 1200

Prior KnowledgeStudents should have some knowledge of basic test equipment and electronic principles as outlined in Unit 1. Teachers should review acceptable Internet use policies as established by the school board.

Before working in a shop environment, students must be aware of general shop rules and requirements, as well as safety rules for specific tools and machines (e.g. safe operation, guard placement and the use of safety glasses). Teachers should review safety rules discussed in Unit 1, and initiate discussion of new tools and processes to be used in this unit. Teachers must verify student’s knowledge of any new safety issues through either a signed “safety passport’ (Appendix B), and/or a check on safety knowledge. Shops must be kept professionally clean at all times. It is to the student's benefit to spend time at the end of each class to prepare the lab for the next class.

Unit Planning NotesThe activities in this unit are designed to provide the opportunity for students to see how electronic circuits and components perform, (particularly analog circuits), how to solve problems with electronic circuits, how to problem solve with prototyping and design procedures, and how to manufacture circuits using industry procedures.

Students are expected to maintain the technician’s test bench developed in Unit 1. (Refer to Unit 1: Activity 2). Teachers must remind all students that they must not turn on any circuit until it is approved and signed off. This unit requires a hands-on approach to circuit design and building, and therefore requires the preparation of physical resources, test equipment and associated tools.

If not already completed, the following tools should be prepared before initiating the activities:Test bench equipment:

oscilloscope multimeter

Shop Equipment(for speaker cabinets or project boxes)

table saw (with dado blades for rabbit


signal generator (suggested) DC power supplies batteries circuit simulation software wire cutters wire strippers needle nose pliers safety eyewear

cuts (optional)) jointer sander jigsaw/scrollsaw router Dremel tool nibbler (optional) nail gun (optional) power screwdriver (optional)

Supplies: 555 timer 556, 558 timers, (optional) magnet wire or choke coils variety of diodes, transistors variety of inductors L-Pads speaker wire loudspeakers jumper wires, or multi-conductor wire breadboards

bins (i.e. Tupperware-type) for parts of student projects

solder equipment and associated supplies

(tweeter/midrange/woofer/subwoofer) as required

MDF sheets, stick lumber for loudspeaker cabinets

variety of capacitors and/or variable capacitors

variety of resistors and/or variable resistors

Aspects of these activities are integrated with curriculum from other courses. For example: English expectations of report writing, research and technical documentation skills, Physics and Mathematics expectations for understanding the theoretical aspects of electronics overlap with the material in this unit. Computer courses, in particular Computer Engineering, are useful in dealing with knowledge of computer-based electronic applications and control systems. Design Technology will enhance understanding of consumer electronic product design and the product development process.

It would be beneficial if representatives from local manufacturing industries present in class or conduct tours. Visiting local colleges, university or private electronics labs are recommended for students to develop an awareness of typical electronics facility operations.

Teaching / Learning StrategiesThis unit continues the hands-on project orientation with a variety of teaching and learning strategies, as described in Unit 1. Students will use their test bench setups (from Unit 1) in activities that incorporate designing/ building/ troubleshooting of analog electronic circuits.

Teachers should present students with an itemized list of tasks that need to be accomplished, including timeframes. Students must keep a daily log of their activities. Teachers should arrange activities to keep students busy at all times, i.e. report writing or drawing/illustration while awaiting paint drying or computer resources. Teachers may elect to post the current status of project tasks in the room for planning purposes.

The activities in this unit are designed as "Just In Time" activities, in other words, the facts or skills that are required for a particular task are taught just before they are needed. For example, when students require a resistor for their first circuit (Activity 1), they are presented with the


resistor colour code and the use of resistive elements to control voltage or current to use in the activity.

Activity 1 engages students in investigating the physical parameters and usage of typical electronic devices and components. The first activity, using a 555 timer, it takes the student through the entire process of component designing, breadboard prototyping, computer based circuit simulation, and mathematical calculations in circuit design. Activity 2 involves an investigation of electrical signals through the fabrication and testing of an audio amplifier and loudspeaker crossover filter network. Activity 3 involves fabrication of printed circuit boards (PCB). Through these activities, students should have a good grounding in electronic circuit design and components and the measurement and manipulation of electrical signals.

Teachers can accommodate the variable learning rates of students by allowing increased time for activities, enhancing or compacting course content, assisting during evaluation processes, and/or facilitating peer-tutor assistance where possible.

Note: A construction shop has a different set of safety issues than the electronics facility. Teachers must be qualified to operate in a construction shop facility. A team-teaching approach may be necessary to take advantage of teachers’ individual strengths.

Assessment / EvaluationTeachers must ensure that all students have an opportunity to demonstrate their mastery of the course expectations individually, even when working in a group. This can be accomplished through one-on-one daily conferencing, daily journal log entries, individual deliverables such as reports or presentations, or individually signed elements of reports or forms.

Assessment is an on-going daily process that may include review of a daily/weekly log, (See Appendix D: Sample Daily Log), observations of efforts in problem solving and critical thinking, participation in discussions and self and/or peer critiques. Students are evaluated on project deliverables such as completed circuit designs, test or project synopsis reports, and presentations based on the assessment charts presented in each activity.

ResourcesCrocodile Clips Simulation SoftwareSpectrum Educational Supplies125 Mary StreetAurora, Ontario L4G 1G3Phone: 905-727-6265 http://www.spectrumed.com

Electronic Workbench Simulation Software111 Peter Street, Suite 801Toronto, Ontario M5V 2H1Phone: 416-977-5550 ext. 255

Reference TextsElectronic DictionaryArt of ElectronicsRadio Shack booklists

Reference MaterialsTelephone DirectoriesIndustrial Directories

Internet SitesHow Things Work- http://www.howthingswork.com/


Nuts and Volts Magazine- http://www.nutsvolts.com/


The 555 TimerUnit 2 Activity 1

480 minutes

DescriptionStudents construct an astable oscillating circuit using the 555 timer IC. Students compare the results of formula calculations, circuit simulation software and circuit measurement results to ensure accuracy of calculations and measurements. Students develop a series of circuits based on the 555 timer IC to develop skills in circuit design, fabrication, testing and troubleshooting.

Strands and ExpectationsStrand Overall Specific

Theory and Foundation TVF.02.1WTF2.07.1WTF2.08.1WTF2.10.1W

TF3.01.1WTF3.02.1W

Skills and Processes SPV.01.1WSPV.02.1WSPV.04.1W



Impact and Consequences IC2.01.1W IC2.02.1WSee Appendix E for full description of TGJ3E expectations

HRDC NOC Specialized Skills2133 Electrical and Electronics Engineer

2133.1.1 2133.1.2 2133.1.3 2133.1.4 2133.1.62241 Electrical and electronics engineering technologists and technicians

Technologists 2241.1.1 2241.1.2 2241.1.3 2241.1.5Technicians: 2241.2.1 2241.2.2 2241.2.4 2241.2.5 2241.2.6

2241.2.7 2241.2.82242 Electronic service technicians (household & business equipment)

2242.1.3 2242.1.47332 Electric appliance servicers and repairers

Small Appliance Repairers 7332.1.47245 Telecommunications line and cable workers

7245.1.57246 Telecommunications installation and repair workers

Telecommunications Service Testers 7246.3.29483 Electronics assemblers, fabricators, inspectors and testers

Assemblers 9483.2.2 9483.3.5 9483.4.1 9483.1.1

See Appendix F for full description of NOC Specialized Skills

HRDC NOC Essential Skills numeracy decision making writing problem solving reading using documents

See Appendix A for Essential Skill rubrics

Unit 2: Activity 1 - 28 - TGJ3E (Microelectronics)

Prior KnowledgeAs students will use the test bench established in Unit 1, prior knowledge includes:

1. basic test equipment identification and associated terminology;2. basic safety procedures, (but should be reviewed in any case);3. simple algebraic equation manipulation;4. simple graphic and report production techniques.

Planning NotesTeachers must arrange the following equipment and supplies. Safety glasses should be made available to participants of the equipment tear down, ideally all students should be issued safety eyewear.Test bench equipment:

Oscilloscope function generator (for demo) stop watch frequency counter multimeter capacitance meter DC power supplies or batteries (9V) circuit simulation software wire cutters wire strippers needle nose pliers safety eyewear calculators

Supplies: 555 timer 556, 558 timers, (optional) variety of capacitors and/or variable

capacitors variety of resistors and/or variable

resistors jumper wires, or multi-conductor wire breadboards bins (i.e. Tupperware-type) for parts of

student projects small speakers for sound generator

experiments

Other resources necessary for this activity include: teacher-developed handout detailing assignment requirements, (Appendix 2.1.1); handout detailing schematic circuit for a 555 oscillating multivibrator (Appendix 2.1.2) handout detailing test report format (Appendix 2.1.3) sample working prototype (optional)

By introducing electronic circuit components and circuit basics in the context of solving a specified problem, students can be taught the basics of analog electronics and electronics theory to be applied in any further circuit-design problem. This hands-on approach is meant to take the place of "theory lessons" conducted in isolation of the application. Teachers will demonstrate components and techniques and allow time for students to apply this knowledge to the task of circuit building

Teaching / Learning StrategiesIn this activity students build a 555 timer-circuit (multi-vibrator) from a schematic diagram to a specified frequency. This activity aims to develop the skills of schematic reading, circuit prototyping and testing, troubleshooting and test report writing. Students build a variety of circuits based on the 555 timer.

Stage 1The first stage of this activity is divided into three components:

1. Calculating frequency of a 555 timer circuit using the mathematical formula;2. Calculating frequency of a 555 timer circuit using circuit simulation software;


3. Calculating frequency of a 555 timer circuit by constructing a physical circuit and measuring resulting frequency.

In using these 3 methods, students can observe the importance of verifying results through a variety of methods. Students will also review the methods used to verify and troubleshoot electronic circuits.

Students are arranged in pairs or teams as required by classroom resources. (Ideally students work individually).

Students are handed the Project Design Brief, outlining the schematic of the multi-vibrator, the deliverables and associated timelines (Appendix 2.1.1). Teachers describe the procedures of prototyping circuits using breadboards, and reinforce their knowledge of Ohm's Law and the physical relationship of voltage/current/resistance. Electron flow and the basic elements of circuits such as power source, conductive paths and load are discussed. Basic passive components are demonstrated: resistor, capacitor, LED, IC, power source and other load components such as bells, speakers, buzzers, motors, etc.

Teachers describe the concepts of frequency, amplitude and electromagnetic waves. Teachers demonstrate the types of waves (square, sine, sawtooth) and the meaning of frequency and amplitude through the use of a function generator and oscilloscope. Teachers then describe how the 555 timer can be used to generate a square wave signal of determined frequency dependent on the values of external resistors and capacitors.

Teachers illustrate the formula for calculating frequency of the multivibrator, and set the target frequency for the student's first circuit, (a visible frequency such as 1 or 2 Hz). Students then calculate the values for components for their circuit by manipulating the equation. Students record their calculations in their test report notes.

Teachers demonstrate the symbols of a schematic diagram and their physical counterparts. After a brief introduction to resistors and the resistor colour code, Students then locate the appropriate values for their circuits. This is repeated for capacitors and LEDs. Safe handling and operational parameters of the 555 are discussed and given to students. Students collect their components and assemble the circuit with assistance from the teacher.

When teachers give the OK, students power their circuit and time their resultant frequency (through stopwatch or frequency counter). Students use troubleshooting techniques to determine problems if required. When successful, students will record results in their test report notes.

If available, students use circuit simulation software (such as Electronic Workbench, Tina or Crocodile Clips) to build a virtual representation of their circuit. Students run the simulation and obtain the frequency using the measured values of the physical components.

Students compare notes of the three methods of determining frequency, and make observational comments as to the closeness of the values. If any result is significantly apart from the others, or all three are different, then the student must record these results and diagnose the reasons for the discrepancy.

Stage 2Students are given circuit diagrams of other circuits based on the 555 timer. The students task is to complete each circuit and compose a test report. These circuits include: (see Resources for this activity for circuit ideas)

astable multivibrator with speaker in place of LED pulse generator (given a frequency, determine component values) toy organ


chirp generator sound effects generator tone burst generator stepped-tone generator monostable or one-shot trigger cascaded timer (using two 555s or a 556) intervalometer event-failure alarm frequency divider

Teachers may elect to test student's knowledge of vocabulary through oral presentations or written tests.

VocabularyStudents should be able to define the following terms, components and/or processes:

analog electronics digital electronics resistance resistor ohms colour code Voltage EMF DC Current ampere load IC 555 timer diode LED capacitance capacitor Farads frequency amplitude period pulse width duty cycle monostable astable multivibrators switch debouncer electromagnetic wave sine wave square wave Hertz (Hz) function generator voltmeter ohmmeter capacitance meter frequency counter oscilloscope time base beadboard SI measurements: pico, micro, milli, kilo, mega

Assessment / EvaluationStudents will be assessed and evaluated on several aspects of this project: demonstration of vocabulary knowledge (verbally, oral presentation, written test); test reports (initiative, depth of content, presentation, originality); verbal presentation (depth of understanding of subject, quality and effort of presentation).


555 Timer Assessment RubricCriteria

Students will: Level 1 Level 2 Level 3 Level 4

KnowledgeTVF.02.1WTF2.07.1WTF2.08.1WTF2.10.1WTF3.01.1WTF3.02.1W

Student displays limited knowledge of identified concepts and terminology

Student demonstrates some knowledge of identified concepts and terminology

Student demonstrates considerable knowledge of identified concepts and terminology

Student exhibits exceptional knowledge of concepts, terminology and/or relationships

Demonstrates little initiative in learning terminology and relationships

Demonstrates limited initiative in learning terminology and relationships

Demonstrates considerable initiative in learning terminology and relationships

Demonstrates exceptional initiative in learning terminology and relationships

InquirySPV.02.1W SP2.04.1WSP2.05.1WSP2.06.1W

Only with constant supervision, safely assembles circuits

With occasional supervision and reminders, safely assembles circuits

Safely and methodically assembles circuits

Safely and methodically assembles circuits

Demonstrates limited initiative in troubleshooting circuits

Demonstrates some initiative in troubleshooting circuits

Demonstrates considerable initiative in troubleshooting circuits

Demonstrates considerable initiative in troubleshooting circuits

Needs constant supervision to follow procedures

Needs supervision to follow procedures but improves

Follows procedures independently and accurately

Works efficiently and independently, helps others to work efficiently

CommunicationSP1.03.1WSP2.01.1WSP3.01.1WSP4.02.1W

Student's report demonstrates limited clarity, knowledge of facts or accurate conclusions

Student reports demonstrates some accuracy and requires some further effort to communicate more clearly

Student reports clearly communicates the ideas and issues and demonstrates insightful conclusions

Student communicates meaningful information with an exceptional degree of clarity & with a strong sense of audience and purpose

Reports and diagrams contain major heading omissions, requires rewrite

Reports and diagrams contain minor omissions, requires some remedial work.

Considerable care in producing reports and diagrams, all elements covered.

Exceptional care in producing reports and diagrams, contains evidence of extra research

ApplicationSPV.01.1WSPV.04.1WSP1.01.1WSP1.02.1WSP2.02.1WSP4.01.1WSP4.03.1W

Student works safely and cleanly only with constant supervision & reminders

Student works safely & cleanly with some required supervision

Student works safely, cooperatively & cleanly with minimal supervision and demonstrates some leadership skills

Student assists and supervises others to work safely & cleanly, demonstrates leadership skills

Requires further work in mathematical and scientific reasoning

Requires more effort in mathematical and scientific reasoning in reporting

Demonstrates clear and concise mathematical and scientific reasoning in reporting

Demonstrates initiative in applying mathematical and scientific reasoning throughout work


Accommodations Strategies to accommodate the variety of learning styles in the classroom may include:

additional handouts to illustrate discussion material; additional time allowance for completion of poster materials; flexibility in acceptable formats for presentations; additional research assignments; concentrated assistance with concept identification; additional one-on-one time by teacher or peer tutors; alternative activities to meet student needs; providing enrichment opportunities such as requirements for more in-depth research.

If required, consultations should be held with students, parents, resource, guidance and special education departments when required to assist in creating an educational plan (IEP) for individual students.

ResourcesSimulation Software

Crocodile ClipsSpectrum Educational Supplies125 Mary StreetAurora, Ontario L4G 1G3Phone: 905-727-6265http://www.spectrumed.com

Electronic Workbench111 Peter Street, Suite 801Toronto, Ontario M5V 2H1Phone: 416-977-5550 ext. 255

Books, Texts Mims, Forrest M. Engineer's Mini-Notebook, (series). Radio Shack/Archer, USA. 555 Timer IC

Circuits, 1984. Cat. 276-5010 Petruzella, Frank D. Introduction to Electricity and Electronics. McGraw-Hill Ryerson, Toronto,

1986. ISBN 0-07-548899-X (Book 1), ISBN 0-07-548900-7 (Book 2)

WebsitesElectronics for Beginners- ourworld.compuserve.com/homepages/g_knott/Alex’s Electronic Test Bench (glossary and resource catalog)- www.iserv.net/~alexx/index.htmePanorama, portal for everything electronics- www.us-epanorama.net/Williamson Labs information on electronics- www.williamson-labs.com/home.htm


Appendix 2.1.1: 555 Timer Design Brief

Title: Project: The 555 Timer

Activity:Design and build a timer circuit for a variety of digital and analog circuits

Course: Communications TechnologyGrade 11 Workplace

Time: 8 -10 hours Date:

RATIONALE

Many circuits including digital switches, timers, counters, light and sound effects generators require a timing mechanism to produce a steady digital pulse. One of the time-honoured methods uses a 555 IC, a linear IC that can be wired to produce a variety of pulses. Wiring a timer using the 555 is a great project to learn about basic digital circuits, RC (resistor-capacitor) circuits, using test instruments such as multimeters, capacitance meters and oscilloscopes, breadboarding and troubleshooting, all skills that are required to develop more sophisticated electronics. This project will lead to many devices used on future electronics projects.

THE ASSIGNMENT

Develop a timing circuit using the 555 timer IC. Use timing formulas to determine the frequency of the circuit and test instrumentation to verify a working circuit.

LEARNING EXPECTATIONS: You will:

1. design and construct electronic circuits using discreet components2. test and verify operations of electronic circuits3. calculate periods and frequencies using mathematical formula4. use computer simulations to calculate circuit performance5. write technical test reports

TOOLS AND MATERIALS555 Timer handout calculator multimeter oscilloscopefrequency counter capacitance meter breadboard alligator clips555 timer IC variety of capacitors resistors LEDsmini-speakers power supply (9V battery

or bench supply)simulation software


EVALUATION# Deliverable #

periodsMark

weighting (%) Notes

1 Test report 2 40 Math calculations, diagrams, test results, observations

2 Completed circuits 5 40 Clean, precise work3 Vocabulary test/report 2 20

TOTALS 9 100

NOTES

ALL CIRCUITS MUST BE INSPECTED BY TEACHER BEFORE POWER IS APPLIED

All reports must be word processed, diagrams or images to be created using illustration or CAD software.

Each individual in a group or team must hand in their own reports.

WHEN IN DOUBT, ASK!

VOCABULARY

analog electronicsdigital electronicsresistance/ohmscapacitance/Faradscapacitorresistorcolour code (resistors)voltage/voltsIC

555 timerbreadboardvoltmeterohmmetercapacitance meterfrequency counteroscilloscopetime basesignal

square wavefrequency/Hertzperiodpulse widthduty cyclemonostable and astable multivibratorsswitch debouncerSI measurements: pico, micro, milli, kilo, mega

PROJECT STEP STUDENT ACTIVITIES

1Read the 555 Timer Project Handout and review circuit designs to become familiar with and note the terminology, calculations and circuit diagrams. Calculate the pulse width or frequency of the circuit you have been given. Retain all calculations and notes for the final report.

2 Obtain components, breadboard, etc. and build the circuit required. Obtain permission from the instructor to apply power to circuit. Test and troubleshoot till you have a working circuit. SHOW COMPLETE CIRCUIT FOR MARKING

3Develop the test report and include circuit diagrams, calculations and results in an engineering test report fashion. Include log sheets. Include vocabulary if required. HAND IN REPORT FOR MARKING

4 Construct and test circuits based on the 555 and 556 timer ICs as given by your instructor.


Appendix 2.1.2: 555 Timer Handbook

THE 555 TIMER PROJECTMany devices, including clocks, timers, counters and even special effects generators require a source of constant pulses to do their job. This can be accomplished with oscillators or timers...in which the 555 timer is a common example. The 555-timer chip can be used for a variety of projects which require steady square pulses such as digital electronic mechanisms, timers, counters, switches, flashers and sound effects generators.

The 555 Timer Project will introduce you to basic electronics: components such as resistors, capacitors, diodes, ICs; breadboarding and wiring and measurement tools such as the multimeter, the oscilloscope, the frequency counter and the capacitance meter. After completing this project you should be ready to tackle the most complex circuits... it’s all down hill from here!

THE 555 TIMER

The timer can perform a variety of functions based on the circuitry surrounding it. It has 3 modes:1. Monostable: “one-shot”, “pulse stretcher”; takes an analog signal such as a switch and produces

a clean square pulse. It is used in switch debouncing, required in digital electronics for example.2. Bistable: can flip from one state (high/low, on/off,...etc.) to the other; not used in timing circuits or

from timer ICs.3. Astable: “multivibrator”, “clock”, “square wave generator”; from input signal such as switch, will

constantly flip from one state to the other in sequence.

We will be building an astable circuit. 555s operate from +4.5 V to +18 V, with +9 V to +12 V the most stable, however it is also great for +5 V TTL operations in digital electronics. We will concentrate on +9 V, using a 9-V battery.

NOTES:For critical timing, 1% tolerance resistors should be used. Use a variable resistor to tune resistances if real critical. Capacitors generally have wide tolerances and plastic film is better. For capacitance from 1uF to 10uF, use tantalums. Over 10uF may require electrolytic, which have wide tolerances. Also note that the capacitor to ground on pin 5 is not required, but desirable for stability. A 0.01uF capacitor is desirable.

THE 555 PINOUT (see diagram)

The 555 Timer IC is an 8 pin DIP. The pinouts are noted below:Pin 1: GROUND connected to ground (reference voltage)Pin 2: TRIGGER input, initiates timing sequencePin 3: OUTPUT output of IC, connected to other devicesPin 4: RESET cancels current timing sequencePin 5: EXT. CONTROL not generally used, can be used for external control voltagesPin 6: THRESHOLD sets internal switching pointPin 7: DISCHARGE discharges external capacitor, senses end of cyclePin 8: Vcc positive voltage supply (+4.5 V to +18 V)


Notes:


MONOSTABLE MODE (see diagram)

The monostable mode is useful for “cleaning up” a switch such as a push button or toggle. These analog devices produce spikes which can produce unwanted effects. The monostable timer takes the switch’s signal and produces a clean square output. The monostable 555 timer requires a capacitor and a resistor to set the pulse width. Note that the output is LOW until triggered by a negative input pulse, then it will go HIGH with a length of pulse specified by:

T=1.1(R1)(C1)

where R1 is in ohms and C1 is in Farads.

For example:

R1=22KohmsC1=0.33µF

T=1.1(R1)(C1)T=1.1 X 22000 Ω X 0.00000033 FT=0.008sT=8 ms

MONOSTABLE EXAMPLES

R1 C1 Pulse

Circuit 2 100 K 25µF 2.75 msCircuit 3 470 K 50µF 25 sCircuit 4 1 M 100µF 110 s

This circuit can produce from pulse widths from about 10ms to the limits of R1 and C1. Try ranges of R1 from 100 Ω to 13M Ω, 10K to 1M are the best for stability and reliability. C1 should be 100pF minimally to avoid stray capacitance, use capacitors in parallel to create greater capacitance.


Notes:


ASTABLE MODE (see diagram)

The 555 can be used in an astable mode to create clock circuits, tone generators, frequency dividers, light triggered timers, event failure alarms, etc. As the input goes HIGH, the output flips from HIGH and LOW in a continuos cycle. Two time periods must be calculated: the HIGH time period and the LOW time period, (the length of time it stays HIGH and LOW respectively). A complete cycle from HIGH to LOW is known as the period (T).

TH = 0.693(C1)(R1 + R2)TL = 0.693(C1)(R2)TOTAL Period (T) = TH + TLFrequency =

therefore:

Frequency =

EXAMPLE ASTABLE R1 R2 C1 Freq. (Hz)

Circuit 1 470 K 470 K 0.22 µF 4.65 HzCircuit 2 470 K 470 K 50 µF 0.02 HzCircuit 3 2.2 K 4.7 K 0.01 µF 12 453 Hz

Note that increasing capacitance decreases frequency. Also note that if the LED stays “ON”, it may that the frequency is too high for you to see the blinking. Try experimenting with different combinations.

The DUTY CYCLE is the ratio of TH/T, and is an indication of the amount of time the cycle is HIGH compared to LOW. A square wave would have a 50% duty cycle. Making the value of R1 very small compared to R2 will produce a close square wave.

The upper limit of timing with a 555 timer is approximately 10-15 minutes. Cascading 555s or using the dual timer (556) or quad timer (558) can provide longer timing sequences. Combining timers and connecting speakers can produce a variety of sound effects generators. (Use a capacitor in series with the speaker to protect it from DC voltages).

OTHER NOTESResistors: devices that restrict electric flow and act as “taps”, controlling the amount of flow

(current) in a circuit. Is used to protect devices from high currents, direct current to circuit pathways and divide voltage (electrical pressure) into different circuit pathways. Measured in Ohms.

Capacitors: devices that can store a charge, (negative and positive) and hence act as temporary batteries. Caps are used as power storage; in series with resistors to change timing, (by holding and then slowing the release of current); and are used as filters to absorb low frequencies and pass on high frequencies. Capacitance in measured in Farads, most commonly micro-Farads (uF) or pico-Farads (pF).

LED: light emitting diode, emits light when forward biased.


Notes:


555 Timer Project: Some Notes Concerning Capacitors

Capacitors come in a wide variety of types, materials, sizes, shapes, labels, colour codes, etc. and may be confusing for the beginning electronics student. They also come in fairly wide tolerances, so the use of a capacitance meter is recommended. Capacitance is measured in Farads, usually in microfarads (µF) or picofarads (pF). Capacitors also have a voltage rating, which is how much voltage it can take, in practise half that number is used for the working voltage. Variable caps are called trimmers.

A capacitor is constructed of two metal plates separated by an insulator called a dielectric. It stores electrical energy by building up voltages on the metal plates (opposite charges). Dielectrics used are air, mica, plastic, ceramic and metal oxide, and in the old days by oiled or waxed paper. The size of the metal plates, the distance between them and the dielectric material determines how much charge it can hold, called the capacitance. For large plates, they are rolled in cylinders to save space.

MICA CAPACITORShigh working voltages…determined by size, sealed against moisture, capacitance and tolerance marked by colour dots

CERAMIC AND MYLARceramic: disc or cylindrical shapes, mylar: “drop” shaped, colour code can be bands, or dots, otherwise marked numericallyif whole number: picofarads, if decimal number: microfarads, Colour code always in picofarads, tolerance may be marked by letter, not marked is +/- 20%miniature capacitors may have picofarad value marked in three letter code; first two numbers are digits followed by multiplier (or number of zeroes), i.e. 104Z

ToleranceLetter 10 pF or LESS

(in +/- pF)OVER 10 pF

(in +/- %)C 0.2D 0.5F 1.0 1G 2.0 2J 5K 10M 20

COLOUR DIGITS MULTIPLIER Tol. > 10pF, in % Tol. < 10pF, in pFblack 0 1 20 2.0brown 1 10 1

red 2 100 2orange 3 1000yellow 4green 5blue 6 5 0.5violet 7gray 8 0.01 0.25white 9 0.1 10 1.0

ELECTROLYTIC CAPACITORSusually greater than 1.0 µF, mostly polarized, .i.e., one lead is marked either negative or positive. Must be connected with correct polarity. Values often marked, sometimes with MFD, meaning µF.


Appendix 2.1.3: Engineering Test Report Format

All engineering test reports must include:

Overall

COVER SHEET, with: company name and logoproject titleyour nameteam member namesclassdate

EACH PAGE includes: company nameclassdate

Contents

PURPOSE OF PROJECT

DESCRIPTION OF PROJECTinclude graphics, sketches, drawings, charts, all graphics labeled and/or titled

METHODS includes calculations

PROJECT RESULTS

PROJECT SYNOPSIS analysis of resultswhat could be done betterhow to improve next project resultshow you could improve as a scientist or engineer

DAILY LOG compiled from daily journal entrieshours worked on project


Appendix 2.1.4: ELECTRONIC INSTRUMENTATION PRIMER

MultimeterMeasures voltage (“electron pressure”) in Volts (V)Measures resistance (the “flow control”) in Ohms Measures current (“the flow”) in Amperes (A)These three make up Ohm’s Law: V=IR (Voltage= current x resistance). NOTE: resistance must be measured without power to the circuit, and current must be measured as part of the circuit: i.e. electrons must flow the meter to be measured.

Capacitance MeterMeasures capacitance, the amount of static charge that can be stored in a capacitor. Capacitance is measured in Farads, typically micro- or pico-Farads. (µF or pF)

Inductance MeterMeasures the amount of inductance, or reverse voltage generated by a coil or choke. Inductance is a factor of electromagnetics and is measured in Henrys (H). Can be thought of resistance due to a changing current/voltage.

OscilloscopeMeasures time varying signal, shows voltage change over time. Usually has 2 or more channels to compare signals.

Frequency CounterCounts pulses or signal peaks in a time varying signal

Function Generator A function generator (or signal generator) supplies a test signal or waveform to test circuitry. It usually can supply a square wave, (to test digital circuits), a sawtooth wave and a sine wave.

DC Power SuppliesDC Power Supplies supply clean direct current or steady voltage to the circuit, like a battery though cleaner and more stable.

Electron MotionElectronic devices operate by the movement of electrons through conductors, e.g. wires, and electronic components. Electron parameters are described by the following basic quantities:

ChargeSymbol: q, unit: coulomb (C) Charge is an amount of electrons. One coulomb is the charge of 6x1018 electrons.

CurrentSymbol: I, unit: ampere or amp (A) Current is the rate of flow of charge, i.e., the number of coulombs flowing past a point per second. One amp is equal to one coulomb per second.


VoltageSymbol: V or E, unit: volt (V) Voltage (also called potential, potential difference, potential drop, or electromotive force - EMF) is the electronic potential energy between two points, and is the driving force that causes charge to flow. One volt is defined as the potential difference that requires one joule of energy to move one coulomb of charge. Voltage is always measured relative to some other point in a circuit, e.g., the potential across a resistor. Voltage measurements made at a single point in a circuit are made relative to the earth (ground), which is assigned an "absolute" voltage of zero.

ImpedanceSymbol: Z, unit: ohm Impedance is the degree to which an electronic component impedes the flow of current. In general it is a frequency-dependent quantity. The impedance of a resistor is also called its resistance. The impedance of capacitors and inductors is also called their reactance. Capacitors consist of a dielectric material separating two parallel plates. They are used to hold charge or to transmit an ac signal and block a dc signal.

CapacitanceSymbol: C, unit: farad (F) Q = CV, I = C(dV/dt)Capacitance is the amount of charge a capacitor can hold per volt. The ability of a dielectric material between conductors to store electricity when a difference of potential exists between the conductors. The unit of measurement is the Farad “F”, which is the capacitance value that will store a charge of one Coulomb when a one volt potential difference exists between the conductors. In AC, one Farad is the capacitance value which will permit one Ampere of current when the voltage across the capacitor changes at a rate of one Volt per second.

InductanceSymbol: L, unit: henry (H) Inductance is ... V = L(dI/dt)An inductor is a coil of wire that stores energy as a magnetic field. The coil is usually wrapped around an iron-containing core, which increases the amount of energy that can be stored by the inductor.


Audio Electronics: Signal ProcessingUnit 2 Activity 2

800 minutes

DescriptionStudents develop bridge rectifiers, filters, and transistor and/or operational amplifier (op-amp) amplifiers to condition and amplify audio level signals. Through this activity, students learn the basics of semiconductors and their applications, as well as processing electromagnetic signals. This activity leads into Activity 3: Project Loudspeaker, in which audio signals are filtered and used to power speaker systems.

Strands and Expectations:Strand Overall Specific

Theory and Foundation TVF.02.1W

TF2.05.1W TF2.10.1W TF2.12.1W TF2.13.1W

TF2.14.1W TF3.01.1W TF3.02.1W

Skills and Processes SPV.01.1W SPV.02.1W SPV.04.1W



Impact and Consequences IC2.01.1WSee Appendix E for full description of TGJ3E expectations

HRDC NOC Specialized Skills2133 Electrical and electronics engineers

2133.1.1 2133.1.3 2133.1.4 2133.1.62241 Electrical and electronics engineering technologists and technicians

Technologists:2241.1.1 2241.1.2 2241.1.3 2 241.1.42241.1.5 2241.1.6

Technicians: 2241.2.1 2241.2.2 2241.2.4 2241.2.5 2241.2.62241.2.7 2241.2.8

2242 Electronic service technicians (household and business equipment)2242.1.1 2242.1.2 2242.1.3 2242.1.4 2242.1.5

2243 Industrial instrument technicians and mechanics2243.1.2 2243.1.3 2243.1.4

2244 Aircraft instrument, electrical and avionics mechanics, technicians and inspectors Aircraft Instrument Mechanics and Technicians 2244.1.1 2244.1.2Avionics Mechanics and Technicians 2244.2.1

7245 Telecommunications line and cable workers7245.1.4 7245.1.5

7246 Telecommunications installation and repair workers Telephone Installers and Repairers 7246.1.1Switch Network Installers and Repairers 7246.2.1 7246.2.2 7246.2.3Telecommunications Service Testers 7246.3.2 7246.3.4 7246.3.5Telecommunications Equipment Technicians 7246.4.2 7246.4.3


7247 Cable television service and maintenance techniciansCable Television Service Technicians 7247.1.3Cable Television Maintenance Technicians 7247.2.3

7332 Electric appliance servicers and repairers Small Appliance Repairers 7332.1.3 7332.1.4Major Appliance Repairers/Technicians 7332.2.3 7332.2.4 7332.2.5

9483 Electronics assemblers, fabricators, inspectors and testersAssemblers 9483.1.1 9483.1.3Inspectors 9483.3.1 9483.3.4 9483.3.5Testers 9483.4.1 9483.4.3 9483.4.5

9484 Assemblers and inspectors, electrical appliance, apparatus and equipment manufacturing Assemblers 9484.1.6Inspectors and Testers 9484.2.1 9484.2.1


HRDC NOC Essential Skills reading job-task planning problem solving decision making numeracy working withothers


Prior KnowledgeThe test bench established in Unit 1 and equipment setup as in Unit 2: Activity 1 will be used in this activity. Prior knowledge includes:

basic test equipment identification and associated terminology; basic safety procedures, (but should be reviewed in any case); prototyping circuits from schematics; schematic symbols of basic components; simple algebraic equation manipulation; simple graphic and report production techniques.

Planning NotesIn addition to the equipment and supplies listed in Unit 2: Activity 1, the following items are required:

assorted diodes, transistors, op-amps relays, SCR's etc. if required for

specific projects microphones (for amplifier input,

optional) sound level meter (optional)

capacitance meter 4 ohm/8 ohm speakers AC step down transformers, (optional) silicone wafers (for demonstration)

There is a wide variety of amplifier circuits available. Teachers may choose to purchase kits (such as a 1W audio amplifier) to allow students to quickly practise signal processing and measurement techniques. See the end of this activity for examples, and Resources for sources of kits and components.

Other resources necessary for this activity include: teacher-developed handout detailing assignment requirements, (Appendix 2.2.1); handout detailing schematic circuits for amplifiers, etc. (Appendix 2.2.2) handout detailing test report format (see Appendix 2.1.3 in previous activity) sample working prototype circuits (optional)


The P-N junction, diode and transistor theories are covered in this activity. While some theory should be discussed before initiating circuit breadboarding, most semiconductor component and circuit basics are discussed in the context of solving a specified problem. This hands-on approach is meant to take the place of "theory lessons" conducted in isolation of the application. Teachers will demonstrate components and techniques, then allow time for students to apply this knowledge to the task of circuit building.

Teaching / Learning StrategiesThis activity connects from Unit 2: Activity 1- The 555 Timer. Teachers may elect to establish new groups or teams for this activity or retain groups from the previous activity.

Audio Electronic CommunicationsTeachers initiate discussions related to the audio frequency portion of the electromagnetic spectrum (20Hz to 20MHz), continuing from Unit 2: Activity 1. Teachers should set-up a frequency generator, oscilloscope and loudspeaker to illustrate the sound associated with frequency to give students a sense of the audio spectrum. During the demonstration, teachers should point out the controls of the oscilloscope and function generator.

Teachers discuss the propagation of sound from source to home or car receivers. Teachers can use illustrations, physical equipment or a combination to highlight key concepts. Teachers should discuss the following concepts:

audio spectrum characteristics (decibel scale) signal filtering, (concepts of attenuation, low pass, band pass and high pass of signal strength) RF propagation through antennas, (how signals are broadcast through the air) electromagnetic signal receiving (how antennas pick up and receive energy, problems in

reception) transformation of electrical energy to mechanical reproduction in loudspeakers (parts of the

electromagnetic speaker, operation of an electromagnetic coil)

Students are then asked to develop one or more of the above concepts in a short research report, including sketches or illustrations.

Rectifiers and DiodesTeachers demonstrate amplitude and frequency modulation of sine waves. Teachers then demonstrate a half-wave rectifier to initiate investigations into the diode and the PN junction. Teachers can use the example of the LED to illustrate diode action. If time permits, a simple demonstration of a seven-segment display may also be used.

Students then construct a full-wave rectifier using discrete diodes. Note: teachers may elect to rectify stepped-down AC power sine waves, and discuss transformers and their operation at this time.

Capacitors are re-introduced (from Unit 2: Activity 1) for their function of filtering ripples. Students complete circuits and develop graphs showing the following:

1. unprocessed sine wave;2. sine wave through half rectifier;3. sine wave through full rectifier;4. sine wave through full rectifier and capacitor filter;5. sine wave through full rectifier and capacitor-choke filter (optional).


At this point, teachers may decide to have students construct a 5V regulated power supply from 60Hz AC. (optional task)

Bipolar and FET Transistor AmplifiersTeachers continue discussion of semiconductors by extending discussions on the PN junction to the PNP and NPN junction. The properties of a transistor to act as a solid state switch and an amplifier of small signals is illustrated by constructing simple circuits and demonstrating the signals on the oscilloscope.

Students are then given circuit diagrams of basic transistor amplifiers to construct and produce a final presentation of their circuit work. Students are asked to produce a final report on their completed circuits.

Op-Amp AmplifierLinear IC op amps are useful to demonstrate sound amplification. Teachers discuss a circuit diagram of a typical 741 or 380 op amp (perhaps using microphone input), and ask students to construct an inverted amplifier or voltage comparator. Students demonstrate their circuits to the class and complete a simple report on the results of their circuit testing.

Students to hand in a vocabulary list or write a formal test:

VocabularyStudents should be able to define the following terms, components and/or processes:

audio frequency semiconductor PN Junction diode forward bias reverse bias LED zener voltage seven-segment display transistor emitter/collector/base NPN/PNP current gain heat sink RF AM/FM rectifier transformer half-wave rectifier full-wave rectifier inductance filter choke waveform cathode anode amplifier integrated circuit linear IC Op amp comparator

Assessment / EvaluationStudents will be assessed and evaluated on several aspects of this project;

functional quality of circuits (clean and detailed work, safe procedures) Test Report on circuits (initiative, depth of content, presentation, originality) presentation (demonstration of depth of knowledge and research)


Assessment Rubric for Circuit Report, Diagrams and PresentationCriteria


KnowledgeTVF.02.1WTF2.05.1WTF2.10.1WTF2.12.1WTF2.13.1WTF2.14.1W

Student displays limited initiative in demonstrating knowledge of identified equipment concepts, terminology and symbols; may be missing important elements

Student demonstrates some adequate initiative in demonstrating knowledge of identified equipment concepts, terminology and symbols; may be missing minor elements

Student demonstrates considerable initiative in demonstrating knowledge of identified concepts, terminology and symbols; no missing required elements

Student exhibits exceptional initiative and depth in demonstrating knowledge of identified concepts, terminology and symbols; shows evidence of further research

Missing some important details on communication systems as prescribed

Missing minor details of communications systems as prescribed

Demonstrates knowledge of communications systems as prescribed

Demonstrates extensive knowledge of communications systems beyond those prescribed

InquirySPV.01.1W

Demonstrates some knowledge of safe handling of troubleshooting procedures but requires constant remedial help in following instructions

Demonstrates safe handling of troubleshooting procedures, but requires remedial help in following instructions

Demonstrates thorough and safe handling of troubleshooting procedures

Demonstrates ability to assist others in following safe and thorough testing and troubleshooting procedures

CommunicationSP1.03.1WSP2.01.1WSP4.01.1WSP4.02.1W

Report and presentation demonstrates limited clarity of information, knowledge of vocabulary basics

Report and presentation demonstrates adequate clarity of information (may have some content and/or formatting errors requiring remediation); adequate or basic knowledge of vocabulary demonstrated

Report and presentation clearly communicates all required concepts and ideas, demonstrates knowledgeable vocabulary

Report and presentation creatively communicates meaningful information with an exceptional degree of clarity beyond required elements

ApplicationSPV.04.1WSP1.01.1WSP1.02.1WSP2.02.1WSP4.01.1WSP4.03.1W

Demonstrates some knowledge into scientific and mathematical principles but requires remediation in important details

Demonstrates adequate knowledge into scientific and mathematical principlesbut may require some remediation in minor details

Demonstrates working knowledge into scientific and mathematical principles

Demonstrates additional research into scientific and mathematical principles


Assessment Rubric for Circuit BuildingCriteria


KnowledgeTVF.02.1WTF2.10.1WTF3.01.1WTF3.02.1W

Demonstrates understanding of only some key terms, component functions

Demonstrates understanding of most key terms, component functions

Demonstrates understanding of all key terms, component functions and unit values

Demonstrates thorough and comprehensive understanding of all terminology; component functions and unit values

Student displays limited initiative in proper use of terminology and symbols, demonstrating knowledge of identified concepts and techniques

Student demonstrates some adequate initiative in proper use of terminology and symbols, demonstrating knowledge of identified concepts and techniques

Student demonstrates considerable initiative in proper use of terminology and symbols, demonstrating knowledge of identified concepts and techniques

Student exhibits exceptional initiative in use of terminology and symbols and demonstrating knowledge of identified concepts and techniques

InquirySPV.02.1WSP2.04.1WSP2.05.1WSP2.06.1W

Demonstrates proper and safe use of testing equipment with some important exceptions

Demonstrates proper and safe use of testing equipment with minor exceptions

Demonstrates proper and safe use of testing equipment as required

Establishes exceptional clean and safe use of testing equipment beyond normal requirements

Demonstrates some knowledge of safe handling of testing, troubleshooting and recording procedures but requires constant remedial help in following instructions

Demonstrates safe handling of testing, troubleshooting and recording procedures, but requires remedial help in following instructions

Demonstrates thorough and safe handling of testing, troubleshooting and recording procedures

Demonstrates ability to assist others in following safe and thorough testing, troubleshooting and recording procedures

CommunicationSP1.03.1WSP2.01.1W

Test report requires important remedial work; contains missing elements or errors, limited documentation of process

Test report requires minimal remedial work; contains some minor missing elements or errors, mostly accurate documentation of process

Test report is clear and contains all required elements without error, accurate documentation of process

Test report contains researched elements beyond requirements; demonstrates professional level work & effort, accurate documentation of process

ApplicationSPV.01.1WSPV.04.1WSP1.01.1WSP1.02.1WSP2.02.1WSP4.01.1WSP4.03.1WIC2.01.1W

Requires constant prodding to work with colleagues in completing assignment

Requires some minimal prodding to work with colleagues in completing assignment

Works well with colleagues in completing assignment

Goes out of way to assist others in completing assignments

Displays some major errors in measurement techniques or calculations

Displays minimal errors in measurement techniques and/or calculations

Displays correct measurement techniques and calculations

Advanced knowledge of measurement techniques and precision calculations

Demonstrates some trouble in identifying important hazards and demonstrates proper safety procedures with a high level of supervision required

Can identify all important hazards and demonstrates proper safety procedures with a low level of supervision required

Can identify all hazards and demonstrates proper safety procedures at all times

Can identify all general and specific hazards and demonstrates a thoroughness in applying proper safety procedures at all times, including before and after class


Accommodations Teachers must use discretion in the depth of project material covered in this activity. There are plenty of circuit designs that can be developed for more advanced students, or teachers may elect to limit the amount of circuits to be built. All students should be able to demonstrate knowledge and skills in audio physics and sound reproduction technology.

Strategies to accommodate the variety of learning styles in the classroom may include: additional handouts such as drawings, terminology sheets, circuit designs, pictorial drawings,

use of simulation labs to facilitate input; additional time allowance for completion of reports; flexibility in acceptable formats for reports; additional one-on-one time by teacher or peer tutors; concentrated one-on-one assistance in hands-on activities; additional research assignments; alternative activities to meet student needs; providing enrichment opportunities such as requirements for more in-depth research; additional responsibilities such as project or facility managers.

ResourcesSuppliersABRA Electronics Corp.5787 PareMontreal, Que. H4P 1S11-800-361-5237Fax [email protected]

Addison Electronics Ltd.8018, 20e AvenueMontreal, P.Q. H1Z 3S7Tel: 514-376-1740

Radio Shack(see local phone book)

Active Surplus 345 Queen Street W.Toronto, Ontario M5V 2A41-800-465-KITS

Electrolab Training SystemsBellevillehttp://www.elabonline.com

Books, TextsPetruzella, Frank D. Introduction to Electricity and Electronics. McGraw-Hill Ryerson, Toronto, 1986. ISBN 0-07-548899-X (Book 1), ISBN 0-07-548900-7 (Book 2)

WebsitesAlex’s Electronic Test Bench (glossary and resource catalog)- www.iserv.net/~alexx/index.htmElectronics for Beginners- ourworld.compuserve.com/homepages/g_knott/ePanorama, portal for everything electronics- www.us-epanorama.net/Williamson Labs information on electronics- www.williamson-labs.com/home.htm


Appendix 2.2.1: Audio Amplifier Design Brief

Title: Project: The Audio Amplifier

Activity: Design and build an audio amplifier to amplify small signals Course: Communications Technology

Grade 11 Workplace


RATIONALE

In any electronic-based communications product, small signals delivered through cable or antennas need to be amplified in order to drive speakers. By utilizing transistors and/or operational amplifier (op amp) devices, you will design and develop a circuit that will take a small signal and amplify the signal to drive speakers. This project helps you understand the uses and function of semi-conductor devices. You will use this knowledge to design and build sound systems for a variety of uses.

THE ASSIGNMENT

Develop a diode rectifier, as well as a transistor and/or op amp signal amplifier.


design and construct electronic circuits using discreet components test and verify operations of electronic circuits calculate periods and frequencies using mathematical formula write technical test reports

TOOLS AND MATERIALS amplifier circuit

diagrams frequency counter resistors op amps (741 or

380)

calculator capacitance meter LEDs mini-speakers

multimeter breadboard diodes power supply (9V

battery or bench supply)

oscilloscope variety of

capacitors transistors simulation

software


EVALUATION

# Deliverable Time (periods)

Mark weighting (%) Notes


2 Completed circuits 4 30 Clean, precise work3 presentation 2 30 Knowledge of facts4 Vocabulary test/report 2 20

TOTALS 10 100

NOTES


All reports must be word processed, diagrams or images to be created using illustration or CAD software. Each individual in a group or team must hand in their own reports.

WHEN IN DOUBT, ASK!

VOCABULARY audio frequency semiconductor PN Junction diode forward bias reverse bias LED Zener voltage seven-segment display transistor

emitter/collector/base NPN/PNP current gain heat sink RF AM/FM rectifier transformer half-wave rectifier full-wave rectifier inductance

filter choke waveform cathode anode amplifier integrated circuit linear IC Op amp comparator


1 Review the circuit diagrams and collect the necessary parts. Retain all calculations and notes for the final report.

2Obtain components, breadboard, etc. and build the circuit required. Obtain permission from the instructor to apply power to circuit. Test and troubleshoot till you have a working circuit. SHOW COMPLETE CIRCUIT FOR EVALUATION.

3Present your circuit to the class. Develop the test report and include circuit diagrams, calculations and results in an engineering test report fashion. Include log sheets. Include vocabulary if required. HAND IN REPORT FOR EVALUATION.

4 Construct and test circuits based on transistor and op amp as given by your instructor.


Appendix 2.2.2: 1-WATT AMPLIFIER- example circuit

PARTS LIST R/1 4.7 Meg ohm Resistor R/2 2.7 Meg ohm Resistor R/3 33 ohm Resistor R/4 1 K ohm Resistor R/5 4.7 meg ohm Resistor R/6 1.8 K ohm Resistor R/7 3.9 ohm Resistor R/8 10 ohm Resistor R/9 10 ohm Resistor R/10 10 ohm Resistor R/11 560 ohm Resistor R/12 22 ohm Resistor C/1 0.22 uf Capacitor C/2 0.22 uf Capacitor

C/3 33 uf Electrolytic Capacitor C/4 0.022 uf Capacitor C/5 220 uf Electrolytic Capacitor C/6 0.068 uf Capacitor D/1 1N 4148 Diode P/1 Trim Pot Q/1 2N 4401 NPN Transistor Q/2 2N 4401 NPN Transistor Q/3 2N 4403 PNP Transistor Q/4 2N 4401 NPN Transistor Q/5 2N 4403 PNP Transistor W/1 Speaker Wire SP/1 Speaker


Appendix 2.2.2: OP AMP AMPLIFIER- example circuit

CIRCUIT NOTES R2 controls 741 preamplifier R3 controls speaker volume Use a fixed 100k resistor for R2 if circuit oscillates or gives distorted output Important: filter power supply connections with 0.1uf capacitors


Audio Electronics: Project LoudspeakerUnit 2 Activity 3

1200 minutesDescriptionStudents design and construct a discreet component loudspeaker system with filter circuits, (crossover network). Through the design, construction and testing of filtered signal circuits, students gain an understanding of the principles of inductance, capacitance, electromagnetism, signal manipulation, sound frequency and sound reproduction in a communication system.

Strands and ExpectationsStrand Overall Specific

Theory and Foundation TVF.02.1W TVF.03.1W

TF2.05.1W TF2.10.1W TF2.12.1W TF2.13.1W

TF3.01.1W TF3.02.1W

Skills and Processes SPV.01.1W SPV.02.1W SPV.04.1W

SP1.01.1WSP1.02.1WSP1.03.1WSP2.01.1WSP2.02.1WSP2.04.1W

SP2.05.1WSP2.06.1W SP3.01.1W SP4.01.1WSP4.02.1WSP4.03.1W

Impact and ConsequencesSee Appendix E for full description of TGJ3E expectations

HRDC NOC Specialized Skills2133 Electrical and electronics engineers

2133.1.2 2133.1.3 2133.1.62241 Electrical and electronics engineering technologists and technicians

Technologists:2241.1.1 2241.1.3 2241.1.5 2241.1.6Technicians: 2241.2.1 2241.2.2 2241.2.4 2241.2.5

2241.2.6 2241.2.89483 Electronics assemblers, fabricators, inspectors and testers

Testers 9483.4.1 9483.4.52242 Electronic service technicians (household and business equipment)

2242.1.1 2242.1.2 2242.1.3 2242.1.4 2242.1.52243 Industrial instrument technicians and mechanics

2243.1.2 2243.1.3 2243.1.49484 Assemblers and inspectors, electrical appliance, apparatus and equipment manufacturing

Inspectors and Testers 9484.2.1 9484.2.17332 Electric appliance servicers and repairers

Small Appliance Repairers 7332.1.3Major Appliance Repairers/Technicians 7332.2.3 7332.2.5

7246 Telecommunications installation and repair workers Telecommunications Service Testers 7246.3.4 7246.3.5Telecommunications Equipment Technicians 7246.4.2

7245 Telecommunications line and cable workers7245.1.4 7245.1.5

7247 Cable television service and maintenance techniciansCable Television Service Technicians 7247.1.3Cable Television Maintenance Technicians 7247.2.3



HRDC NOC Essential Skills problem solving computer use decision making job-task planning finding information numeracy


Prior KnowledgeStudents learn the basics of the electromagnetic spectrum in Activity 2. Prior knowledge therefore includes:

Basic test equipment identification and associated terminology Basic safety procedures, (but should be reviewed in any case) Prototyping circuits from schematics Schematic symbols of basic components Simple algebraic equation manipulation Simple graphic and report production techniques Basic terminology of sound and electromagnetism

Planning NotesThis activity concentrates on the electronics behind the electromagnetic loudspeaker system. The project may lead into the actual construction of a loudspeaker enclosure, or may be restricted to using a prefabricated test box. Considerations before beginning this activity are:

Constructing a loudspeaker enclosure entails a lengthy time allotment, (much more than allocated here), the use of a wood shop facility, a trained wood shop instructor, the materials and associated additional costs. Such an undertaking does take time and effort, and teachers may feel that it takes too much away from the rest of the course.

Used commercial loudspeakers may be used, and therefore the activity would involve refurbishing the sound quality through the design and installation of a new crossover network. Optionally, kits may be purchased that would shorten the time and fund requirements.

Students may be attracted to the program through this activity, and may want to have speaker systems built for their own use. Additionally, this activity could be used as a basis for a school or community project, or for a special event funding drive. You may decide to run this activity as a culminating performance task at the end of the semester.

The expectations assessed and evaluated through this activity can be met through limiting the activity to the design and construction of the electronic circuits for pre-existing loudspeaker systems.

A strategy to accomplish this project might be to develop a loudspeaker enclosure in an initial semester, then use that enclosure as a test system for following semesters.

Alternatively, the design and construction of the enclosure or a set of test boxes may be accomplished in another course, such as Technological Design, Construction or Manufacturing in concert with the Communications Team.

The specific equipment and supplies required are: Component speakers such as tweeters, midranges, woofers, subwoofers Assorted chokes, capacitors, diodes, L-pads, fuses, speaker wire Breadboards, jumpers, perf boards, soldering stations Test bench instrumentation for audio spectrum signals sound level meter (optional) sound spectrum analyzer (optional) audio test CD or cassette (optional) enclosure or enclosure material if constructing speaker systems


Other resources necessary for this activity include: teacher-developed handout detailing assignment requirements, (Appendix 2.3.1); handouts/overheads detailing electromagnetic speaker parts and schematic circuits for

crossover circuits, etc. (Appendix 2.3.2) handout detailing test report format (see Appendix 2.1.3 from previous activity) sample crossover networks (optional, from Addisons, Radio Shack, etc….see Resources)

Teaching / Learning StrategiesLoudspeaker DesignTeachers assemble a range of components including:

Tweeter Midrange Woofer Subwoofer (optional) Dual cone car speaker (optional) Crossover network (best: multi-tap)

Referring to Appendix 2.3.1, teachers initiate discussion about the types of electrodynamic speakers. Teachers ask students to identify the obvious physical characteristics of the tweeter, midrange and woofer. Teachers discuss the physics behind sound reproduction, including electrodynamics, power vs. frequency, measuring sound with decibel scale, etc. Discussions are also initiated about frequency response, damping, distortion, power rating, impedance and dispersion.

Students are asked to take notes during discussions; teacher may provide forms with spaces to fill information to direct note taking. It is important to show students the physical speakers, in order for them to appreciate the concepts. If possible, the teacher may want to drive an old speaker through the audio spectrum to distortion to illustrate cone travel, clipping, power requirements to push air, etc.

Sound PhysicsTeachers should reinforce earlier discussions on the audio spectrum. It would be instructive to use an audio test CD or frequency generator capable of 20Hz to 20MHz to drive types of speakers to illustrate frequency and amplitude concepts. The decibel scale is discussed. A sound-level meter would be useful here to demonstrate sound levels. An oscilloscope should be used to visually demonstrate changes in frequency. This topic leads into a demonstration of filter circuits.

Filter circuitsThe concepts of crossover networks are addressed through a discussion and demonstration of the effects of passing a range of frequencies through a choke and a capacitor. Teachers describe the physics of what these components do to attenuate signals. Teachers demonstrate how to calculate component values to determine frequency cut-off values. (See Appendix 2.3.2) Students demonstrate signal attenuation with components, oscilloscope and function generators. Teachers give students various components and ask them to calculate cutoff frequencies, and demonstrate them on the test bench.

The orders of filter circuits are discussed and illustrated. Students are given a Design Brief to develop various filter circuits, (see Appendix 2.3.1). Students are then asked to develop a test report, evaluating what they have learned, and illustrating circuit diagrams.

EnclosuresTeachers discuss the terminology of speaker enclosure types, demonstrating enclosure types. At this point, teachers either work to build a set of speaker enclosures, or else continue with constructing crossovers for existing speakers


Constructing CrossoversStudents are given specific frequency cutoff points and are asked to develop and test their circuit. Teachers evaluate student knowledge and skills in their circuit design. Once appraised, students build their circuit on perf board or equivalent. Students assemble and test the speaker system.

Assessment/Evaluation Students will be assessed and evaluated on several aspects of this project;

functional quality of circuits (clean and detailed work, safe procedures) Test Report on circuits (initiative, depth of content, presentation, originality) Presentation (demonstration of depth of knowledge and research)

Assessment Rubric for Project LoudspeakerExpectationsStudents will: Level 1 Level 2 Level 3 Level 4

KnowledgeTVF.02.1WTVF.03.1WTF2.05.1WTF2.10.1WTF2.12.1WTF2.13.1WTF3.01.1WTF3.02.1W

Student displays limited initiative in demonstrating knowledge of identified equipment concepts, terminology and symbols; may be missing important elements

Student demonstrates some adequate initiative in demonstrating knowledge of identified equipment concepts, terminology and symbols; may be missing minor elements

Student demonstrates considerable initiative in demonstrating knowledge of identified concepts, terminology and symbols; no missing required elements

Student exhibits exceptional initiative and depth in demonstrating knowledge of identified concepts, terminology and symbols; shows evidence of further research

Student displays limited initiative in proper use of terminology and symbols, demonstrating knowledge of identified concepts and techniques

Student demonstrates some adequate initiative in proper use of terminology and symbols, demonstrating knowledge of identified concepts and techniques

Student demonstrates considerable initiative in proper use of terminology and symbols, demonstrating knowledge of identified concepts and techniques

Student exhibits exceptional initiative in use of terminology and symbols and demonstrating knowledge of identified concepts and techniques

InquirySPV.01.1WSPV.02.1WSP2.04.1WSP2.05.1W

Demonstrates proper and safe use of testing equipment with some important exceptions

Demonstrates proper and safe use of testing equipment with minor exceptions

Demonstrates proper and safe use of testing equipment as required

Establishes exceptional clean and safe use of testing equipment beyond normal requirements

Demonstrates some knowledge of safe handling of testing, troubleshooting and recording procedures but requires constant remedial help in following instructions

Demonstrates safe handling of testing, troubleshooting and recording procedures, but requires remedial help in following instructions

Demonstrates thorough and safe handling of testing, troubleshooting and recording procedures

Demonstrates ability to assist others in following safe and thorough testing, troubleshooting and recording procedures

CommunicationSP1.03.1WSP2.01.1WSP3.01.1WSP4.01.1WSP4.02.1W

Report demonstrates limited clarity of information, knowledge of vocabulary basics

Report demonstrates adequate clarity of information (content and/or formatting errors requiring remediation); adequate or basic knowledge of vocabulary shown

Report clearly communicates all required concepts and ideas, demonstrates knowledgeable vocabulary

Report creatively communicates meaningful information with an exceptional degree of clarity beyond required elements


Project Loudspeaker rubric cont’dApplicationSPV.04.1WSP1.01.1WSP1.02.1WSP2.02.1WSP2.06.1WSP4.01.1WSP4.03.1W

Demonstrates some knowledge into scientific and mathematical principles but requires remediation in important details

Demonstrates adequate knowledge into scientific and mathematical principles but may require some remediation in minor details

Demonstrates working knowledge into scientific and mathematical principles

Demonstrates additional research into scientific and mathematical principles

Requires constant supervision, but does accomplish task in time allotted

Requires some supervision in order to stay on task but does accomplish goals in time frame allotment

Keeps on task until completion, assists others on team to accomplish goals

Demonstrates efficient use of time, organizes work team to accomplish goals

Accommodations Teachers must determine the capabilities of their classrooms and use discretion in the depth of project material covered in this activity. Teachers may elect to limit the task to crossover network design and development, or extend the activity to design and build the entire system. All students should be able to demonstrate the knowledge and skills in audio physics and sound reproduction technology.

Strategies to accommodate the variety of learning styles in the classroom may include: additional handouts such as drawings, terminology sheets, circuit designs, pictorial drawings,

use of simulation labs to facilitate input; additional time allowance for completion of reports; flexibility in acceptable formats for reports; additional one-on-one time by teacher or peer tutors; concentrated one-on-one assistance in hands-on activities; additional research assignments; alternative activities to meet student needs; providing enrichment opportunities such as requirements for more in-depth research; additional responsibilities such as project or facility managers.

Resources

Kits, Magazines, etc.Old Colony Sound LabsPO Box 243Peterborough, NH 03458-0243http://www.audioxpress.com/index1.htm

Speaker Builder MagazinePO Box 494, Dept LDC5Peterborough, NH 03458-0494http://www.audioxpress.com/magsdirx/spkrbldr/

SuppliersShopkit Industries (speaker kits)P.O Box 1573Superior, Wisconsin USA 54880Al Olson ph. 1-800-236-4429ph. 1-715-392-5522http://www.cpinternet.com/~shopkit

ABRA Electronics Corp.5787 PareMontreal, Que H4P 1S11-800-361-5237Fax [email protected]


Addison Electronics Ltd. (excellent source for speakers, etc.)8018, 20e AvenueMontreal, P.Q. H1Z 3S7Tel: 514-376-1740

Active Surplus 345 Queen Street W.Toronto, OntarioM5V 2A41-800-465-KITS

Electrolab Training SystemsBellevillehttp://www.elabonline.com

Radio Shack (crossovers)(see local phone book)

Books, Texts Dickason, Vance. The Loudspeaker Design Cookbook. Audio Amateur Press, New Hampshire,

1995. ISBN 1-882580-100-9 Petruzella, Frank D. Introduction to Electricity and Electronics. McGraw-Hill Ryerson, Toronto,

1986. ISBN 0-07-548899-X (Book 1), ISBN 0-07-548900-7 (Book 2)

WebsitesThe Speaker Building Page - http://www.hi-fi.com/speaker/Audiomatica SA (manufacturer's of CLIO sound spectrum analyzer) –

http://www.mclink.it/com/audiomatica/clioeng.htmSpeakerBuilding.com- http://www.speakerbuilding.com/


Appendix 2.3.1: Project Loudspeaker Design Brief

Title: Project Loudspeaker

Activity:Students design a crossover network for a three or two way loudspeaker system

Course: Communications Technology Grade 11 Workplace


RATIONALE

Loudspeaker systems are ideal for demonstrating the physics and the concepts of electromagnetism, signal manipulation, test measurement systems and signal reproduction. Through the design of a crossover network (a filter circuit), you will have the basic procedures to design and build any electronic device that requires the transmission and receiving of electronic signals.

THE ASSIGNMENT

You will design and build a crossover network for a two-way or three-way loudspeaker system.


manipulate electronic signals calculate inductance and capacitance in order to direct signals to output devices define and describe the types of audio speakers, enclosure types and physical parameters of

speaker systems test and analyze communication signals describe the process of filtering electronic signals illustrate circuit diagrams and write test reports

TOOLS AND MATERIALSCrossover circuit diagrams calculator multimeter oscilloscopecapacitance meter inductance meter breadboard variety of capacitorscoils or chokes resistors fuses L-Padsaudio amplifier speakers (tweeter,

midrange, and/or woofer subwoofer)

either test speaker enclosures or materials for fabricating speaker enclosures


EVALUATION

# Deliverable Time (periods)

Mark weighting (%) Notes


2 Completed circuits 4 30 Clean, precise work3 Presentation 2 30 Knowledge of facts4 Vocabulary test/report 2 20

TOTALS 10 100

NOTES


All reports must be word processed, diagrams or images to be created using illustration or CAD software. Each individual in a group or team must hand in their own reports.

WHEN IN DOUBT, ASK!

VOCABULARYAudio frequency Inductance MidrangeFrequency response Tweeter WooferAmplitude Distortion SubwooferPower Clipping EnclosureDecibels Hertz (Hz) Crossover networkElectromagnet Low pass filter L-padCoil Band pass filter FuseChoke Notch filterImpedance High pass filtercapacitor Cutoff frequencyCapacitance Octave


1 Review the circuit diagrams and collect the necessary parts. Retain all calculations and notes for the final report.

2Obtain components, breadboard, etc. and build the circuit required. Obtain permission from the instructor to apply power to circuit. Test and troubleshoot till you have a working circuit. SHOW COMPLETE CIRCUIT FOR MARKING

3

Test circuits using speakers to listen for sound quality, and using meters to measure signal strength Develop the test report and include circuit diagrams, calculations and results in an engineering test report fashion. Include log sheets. Include vocabulary if required. HAND IN REPORT FOR MARKING

4 Present your findings to class and instructor.


Appendix 2.3.2: Support Materials for Project Speaker

PROJECT SPEAKER TERMINOLOGYSound pressure waves in fluids, gases or solidsFrequency number of peaks per given time periodHertz unit of frequency, cycles per second (Hz)Amplitude loudness or intensity of vibrationsDecibels -ratio of 2 sound amplitudes, (dB), logarithmic scale

-0dB: barely heard 1000Hz signal by human ear in quiet environment

-change in 10dB: twice as loud- 90dB: 109 or billion times louder

Sound Pressure Level (SPL) amplitude of sound in decibelsAmplification increasing electrical signal amplitudeEcho (Reverberation) reflection of direct sound waves off of surfaces

PARTS OF ELECTRODYNAMIC SPEAKERS(see diagram)

driver (coil and magnet)frame or basketbobbinspidersuspension or surroundconedust cap

Piezoelectric speakersElectrostatic speakers


TYPES OF SPEAKERSProject Speaker

Woofers low range, bass, 20 to 1000Hz range from 4" to 16", usually 10" to 12" made of felted paper, polypropylene

Midrange broad spectrum, 1000Hz to 10kHz, most efficient 1kHz to 4kHz best for voices, most instruments range from 3" to 8" paper, cloth, poly some domed for wide dispersion

Tweeter high or treble range, 4kHz to 20kHz usually under 2" paper, plastic, metals suffer from narrow dispersion, horns, baffles, domes

used to disperse sound

Full Range adequate for covering full spectrum typically used in car systems usually inexpensive

Coaxial/Triaxial woofers and midranges or midranges and tweeters with

individual coils in common magnets

Whizzer Cones woofers and midranges with separate cone attached to coil improves frequency response


SPEAKER DESIGN FACTORSProject Speaker

Power Rating amount of power speakers can handle rating in watts RMS two ratings:

1) peak (short duration)2) average (continuos)

if exceeded can overheat coil and cause permanent damage improve by cooling systems, such as ferrofluid most power absorbed by woofer (half of power between 75Hz and 500Hz) typical woofer is 50W to 60W

Magnet Size lager the magnet, the greater force to react to coil usually 15 to 20 oz., some to 50 oz. rare earth magnets best

Cone Material cloth or paper distorts with age poly lasts longer, takes more stress

Suspension folded paper best for ported reflex rolled polyfoam or butyl rubber more compliant for acoustical suspension

Impedance resistance to AC signals, in ohms most systems 8 ohms, some 4 ohms depends on multiple speaker configuration


SPEAKER DESIGN PARAMETERSProject Speaker

Frequency Response range of frequencies an audio system can reproduce accurately usually a variation of speaker output over the range of frequencies flat means perfect response across spectrum if dips in response- sound "colored" measured in decibels (ratio of output power to input power) the higher the dB, the greater the output power for any given input power

Sound Dispersion spreading of sound leaving speaker the wider the dispersion the better speakers omnidirectional up to certain frequencies tweeters worst Dispersion limit frequencies:

15" 880Hz 4" 3.3kHz12" 1.1kHz 2: 8kHz8" 1.65kHz

Damping cone should follow applied signal unwanted motion due to unwanted signals should be damped out speaker components that apply damping:

cone material (stiffness)suspension (compliance to movement)spider (made to restrict motion)magnet (heavier = more shock absorbing)enclosure (air pressure)

Sound Distortion unwanted applied electrical and mechanical noise changes or colours sound by altering or adding frequencies or amplitudes Types:

Harmonic distortion: added frequencies in signal, or imperfect driver behavior at high volumes

Noise: damaged components, raspy sound, i.e., torn cone

Transient response: time delay in responding to rapid signal changes

Clipping: bottoming out of speaker, running out of travel, esp. woofers


CROSSOVER ELECTRONICSProject Speaker

Wiring the SpeakerThe louder it is, the more power, hence the larger (diameter) the wire required to prevent heat and reduce the voltage drop. Also the longer the distance, the larger the wire required (voltage drop).

Wire Gauge CapacityAWG 14 15A AWG 16 6AAWG 18 3A

Speaker PolarityGeneral Rule: red = positive, black = negative or ground, (RCA plugs…note centre post polarity)

ImpedanceInput and output impedance (frequency dependant resistance) must match, i.e. 8, 4 In series circuits, impedance doubles, in parallel circuits it halves.

L-Pads better than fixed resistors to control volume of independent speakers in enclosures. L-Pad: variable resistance, constant impedance

Fuses used inline on the positive terminal to protect speaker from over-current load

A = P Z/

where A = fuse amperage, P = power of speaker in Watts, Z = impedance in ohms

Speaker Enclosures too big: boomy sound too small: flat bass sound


CROSSOVER NETWORKS

COMPONENTS

role of crossover is to protect tweeter or midrange from low freq. overload

crossover freq.: that freq. where you cut off response down to 3dB

Capacitors:used to cutoff lows: (high pass filter), uses principle of RC lag

Coils:cuts off highs, (low pass filter), uses principles of back EMF due tomagnetic field

TYPES OF CROSSOVERS

Note: common midrange crossover: 1500Hz-6000Hz common tweeter crossover: 6000Hz-20kHz 2 kinds of crossover circuits: series and parallel circuits crossovers named by number of drivers: 2 way or 3 way, etc. 3 kinds of crossover filters:

low passhigh passband pass

simplest: 1st order (cutoff slope 6dB/octave) high pass capacitor in series with resistor 3dB is where impedance of cap = impedance of tweeter to move crossover point higher: use smaller capacitor

Common 2 wayWoofer dia. Freq. (Hz)

8” 250010”-12” 1600

Common 3 way8” 1000/5000

10”-12” 700/450015” 600/4500


CALCULATING CAPACITOR (HIGH PASS) VALUE

C = 1/(2 f Xc)

or

C = 15900/(f Rt)

where Xc = capacitance reactance (reactance = “react against”)Rt = impedance of tweeterC = µFf = frequency i.e. 4000Hz

CALCULATING CHOKE (LOW PASS) VALUE

Coils (also called chokes, inductors) used in series with woofer, Inductance (L) measured in Henries or mH

L = 159 Rw/f

where Rw = impedance of wooferf = crossover freq.


SPEAKER ENCLOSURE DESIGNProject Speaker

Enclosures "bare" speakers do not perform well because back sound waves can cancel some waves

from the front, causing distortion speakers are placed in "enclosures" to contain back waves, damp out unwanted

frequencies, improve performance and efficiency, and enhance low frequencies

ENCLOSURE TYPES

Acoustic Suspension air tight enclosure speaker is cushioned or suspended by air inside enclosure (damping)

Infinite Baffle very large sealed enclosure, low suspension or damping

Ported Reflex also called ducted port, bass reflex, Helmholtz resonator) tubed port in enclosure, open to front size and length of port is critical for tuning deeper bass response and higher efficiency

OTHERS Double Woofer Double Chamber Reflex Tapered Pipe Labyrinth or Transmission Line


DECIBEL SCALEProject Speaker

Sound Production Decibel Scale (dB)

Notes

Explosion 130Threshold of Pain 120 Night ClubAuto Horn at 20 ft. 110 Loud Music 30 WHeavy Trucks at 20 ft. 100Train Whistle at 500 ft. 90Vacuum Cleaner at 10 ft. 80Average Traffic at 100 ft. 70Normal Speech at 3 ft. 60 Soft Music 0.01 WLight Traffic at 100 ft. 50

40Soft Whisper at 5 ft. 30Very Soft Whisper at 1 ft. 20

10Threshold of hearing 0


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