Essential Question: How does a circuit designer get the right resistance values ?

Relevance: Resistors are the most basic of electronic components. Virtually all electronic devices such as toasters, computers, lights, etc. are typically modeled as resistors for determining the power requirements of a building.

Resistance Circuits

5. Calculate total resistance for resistors in:

• prevents circuits from being overloaded

• useful for controlling costs

• useful for preventing environmental damage--less pollution, less nuclear waste, less CO₂ emitted

 

Essential Question: What is the difference between AC and DC electrical power?

AC and DC Electrical Power

9. Distinguish between alternating current (ac) and direct current (dc).

• AC --type of current from power plants and portable generators or available from typical household outlets. Can easily change voltage up or down by using a transformer. Good for high-voltage transmission

. This reduces the size of the wires needed and the percentage of power lost due resistance heating of the wires.

• DC--output of batteries and solar panels. In electronic devices such as radios, TVs, and computers, AC power from an electrical outlet is immediately converted to DC for internal use in the device.

12. Explain that, in remote areas of developing countries, electricity supply is based on localized supply not a national grid system. Remote areas of developing countries rely on generators for ac supply, and solar panels for battery-based low-voltage dc supply, as there is not a national grid system. This has implications for portable electronic equipment.

13. Explain that, in developed countries, there will be a national grid, although the voltage will vary between countries, with countries adopting either the US standard or the UK standard.

14. Explain how differences in electrical voltage can impact on the design of electrical and electronic products.

15. Explain the implications for aid agencies of there being no national grid in remote areas of developing countries. Since any electricity supply is locally generated an aid agency can never be certain of the type or availability, hence they often need to supply their own power.

Essential Question: How is a capacitor similar to a spring ?

Capacitors

16. State the unit of capacitance--farad (F), a very large unit, and so capacitors often use microfarad (μF) as their unit.

17. Calculate total capacitance for capacitors in

series: 1 / C_total = 1 / C₁ + 1 / C₂ + ... + 1 / C_n

_{The total resistance value of a group of capacitors in series will always be less than the smallest value of capacitance in the group.}

 

parallel: C_total = C₁ + C₂ + ... + C_n

_{The total resistance value of a group of resistors in parallel will always be larger than the largest value of resistance in the group.}

 

Essential Question: What single component has had the most impact on modern electronics?

Operational amplifiers

Note: there are 2 standards for electronic symbols, 1) the American  and 2) the International Electrotechnical Commission (IEC). These differ in a number of areas. http://www.geocities.com/talkingelectronics/Circuit_Symbols.html

Component	Function	Symbol
		American	International
resistor	Used for reducing voltage and/or current in an electrical circuit. Household appliances can be modeled as resistors.
thermistor	Changes resistance with changes in temperature. Used for measuring temperature.
LDR (light-dependent resistor)	Changes resistance with changes in light level. Used for measuring light level, for example in cameras.
variable resistor	Allows manual adjustment of resistance.
diode	Prevents current from flowing in more than one direction.
cell	The term refers to a battery with a single cell. Batteries are a source of DC power.
push switches	Normally open: A device that closes (turns on) a circuit when pushed and opens the circuit when released. Normally closed: A device that opens (turns off)  a circuit when pushed and closes the circuit when released.
SPST (single pole, single throw) switches	A device that opens or closes a single circuit.
SPDT(single pole, double throw) switches	A device that opens one circuit as it closes a second and vice versa.
lamp	A device that glows when activated.
motor	A device that turns electrical energy into rotational kinetic energy.
LED (light-emitting diode)	A low powered light with a positive and negative connection. Current can only flow through the device from the positive to the negative connection.
loudspeaker	Converts electrical signal (with an audio frequency range) into sound.
buzzer	Sounds a defined tone when activated.
capacitor	Stores and releases electrical energy similar to the way a spring stores and releases mechanical energy.

 

Assessment -- Analysis of Circuit Symbols IB Standard:Circuit Symbols Specifications: Using internet research, create a hand-written table with both American and International symbols for the components shown in objective 20. Deliverable: Place the completed table on the designated turn-in location. Work Group: Individuals.

 

Draw the circuit symbol for an operational amplifier (op amp). general purpose device capable of meeting many purposes differential voltage inputs amplifies a voltage (high gain) single output Define positive saturation: Occurs if there the op amp is connected as shown and  V1 > V2 , Vout =  + Vcc negative saturation: Occurs if the op amp is connected as shown and  V1 < V2 , Vout =  - Vcc Draw a circuit for an op amp used as a comparator. The diagram is the same as shown at left and is set up to give positive or negative saturation when the input voltages are compared.
Describe how resistors can be used to produce a voltage divider circuit. (see circuit at right.) Describe how a voltage divider circuit can be used to generate a reference voltage for one input of a comparator. Connect circuit at right to one of the inputs of an op amp. Explain how the following devices can be used as one of the resistors in a voltage divider: thermistor -- used as a temperature sensor light-dependent resistor (LDR) -- used as a light sensor. http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/square.html
Assessment -- Investigation of voltage divider circuit IB Standard: Voltage divider circuit Specifications: Create two different voltage divider circuits each with an input of 12 volts from a power supply. Calculate the output voltage and compare it to  the measured voltage. Deliverable: A hand written sheet for each group with: a properly labeled drawing of each circuit including how the power supply and voltmeter were connected. A data table with the calculated and measured values along with a % difference between  them. Work Group: individuals.
Draw a circuit for an op amp used as a non-inverting amplifier. Calculate the gain of a non-inverting amplifier. Draw the transfer characteristic for a non-inverting amplifier. Draw an output waveform of a noninverting amplifier, for a given input waveform and gain. Explain the effect that saturation has on the output waveform for a noninverting amplifier.
Calculate the gain of an inverting amplifier. gain = -Rf / R1 Draw the transfer characteristic for an inverting amplifier. Draw an output waveform of an inverting amplifier, for a given input waveform and gain. Explain the effect that saturation has on the output waveform of an inverting amplifier. It clips the top of the wave.

Summative Assessment: Test objectives 1-33

Essential Question: What is a digital computer?

Digital logic

1. Explain the differences between a digital and an analogue signal.

• analog--infinite possible number of values between a lower and upper limit.

• digital--two possible values representing a zero and a one.

2. Explain how a digital signal can be generated from an analogue signal.

3. Describe how the two possible output states of a logic gate can be used as a switch. true = on, false = off

4. Draw circuit symbols for digital logic gates.

• and

• or

• not

5. Draw truth tables for digital logic gates. Identify Boolean expressions for digital logic gates.

6. Design solutions to practical problems using digital logic gates.

7. Design time delays by applying switches and CR circuits as the input to logic gates.

 

Essential Question: How are large-scaled facilities such as chemical and nuclear power plants controlled, so that hey produce the desired output?

Control

8. Draw a block diagram for an open loop system and describe its shortcoming.

• can't respond to changes in environment

• blind -- can't tell if it's working

9. Draw a block diagram for a closed loop control system.

10. Explain how feedback is used in a closed loop control system.

11. Explain the advantages of closed loop systems over open loop systems.

12. Explain why most systems use negative rather than positive feedback.

 

Essential Question: If an entire computer system could be reduced to the size of a grain of rice, what would be the possibilities?

Programmable interface controllers

13. Define programmable interface controller (PIC). A PIC is a small sized computer complete with input, output, and memory capacity. The inputs and outputs are typically voltages. A PIC can be programmed to perform simple tasks.

14. Describe why PICs are ubiquitous in almost all modern electronic products.

• improve performance

• reduce cost

• reduce product development time

15. Identify reasons why PICs are particularly applicable for portable electronic products.

• compact size--often smaller than equivalent circuits made from off the shelf components.

• inexpensive--since one chip can perform many functions, it can be mass produced in very high quantities, hence, lowering cost.

• highly flexible--facilitates rapid prototyping and design changes since even major changes can be easily made in software.

• general purpose--avoids the need for designing specialized integrated circuits

16. Explain how PIC technology has improved the electronic systems in car design.

 

Essential Question: Why does a modern hearing aid not just simply amplify sound ?

Electronics and health

17. Explain how an audiogram represents an individual’s hearing, which may be normal at some frequencies and with losses at other frequencies.

18. Explain that digital hearing aids are able to divide incoming sound into distinct bands, which are individually selected for amplification.

19. Identify the key elements of a digital hearing aid.

• Microphone

• filters for separating frequency bands

• analogue-to-digital converter

• processing to amplify certain frequency bands

20. Explain how a PIC can contribute to the customization of a hearing aid.

 

 

Essential Question: What enables you to communicate over long distances?

Communication systems

21. Define

• bandwidth--The width of the electromagnetic spectrum that a signal occupies

• multiplexing

--To combine multiple signals for transmission over a single line or medium.

• modulation--The process of adding the information contained, for example, in the human voice to a suitable electromagnetic carrier.

• demodulation--The process of recovering the information contained, for example, in the human voice, which had been previously added to a suitable electromagnetic carrier.

• optical fiber

22. Explain frequency division multiplexing. Different data streams are transmitted simultaneously over the same channel by assigning a different  frequency to each data stream. At the other end of the channel, the signal is passed through a series of filters designed to filter out all the frequencies except the one with the desired information.

23. Explain the principles of time division multiplexing.

24. Explain the limitations of copper wires for information transfer.

• electrical resistance: causes loss of amplitude

• susceptible to outside electrical noise

• variable magnetic fields can induce electrical noise in wires

• limited bandwidth
• wire expense

25. Describe an optical fiber.

• long fiber

• transparent material

• specially coated for total internal reflectance

• opaque sheath

26. Describe how fiber optic cables are able to transfer information.

• digital signal: input light (usually a laser LED) is turned on and off rapidly to create a digital signal of zeros and ones.

• total internal reflectance: light shining in one end stays in the fiber and is transmitted through it even if the fiber has bends in it.

27. Explain how fiber optics are able to transfer information in large quantities. Very high bandwidth allows frequency division multiplexing.

28. Draw a block diagram for an optical fiber transmission link.

29. Identify three types of optical fiber.

Type	Description	Advantages (relative to single mode)	Disadvantages (relative to single mode)
single-mode:	new technology--very thin typically10 μm diameter	thinness facilitates bundling into light-weight multi-fiber cables. flexible thinness helps prevent degradation of light pulses due to multiple reflectance paths, fibers--can have longer length
multimode (stepindex and graded index)	Old technology--about 10 times thicker than single mode		stiff heavy and bulky thickness causes degradation of light pulses due to multiple reflectance paths, fibers can't be as long as single-mode
plastic optical fiber (POF)	Clear plastic fiber	inexpensive to produce	attenuates the signal more than glass fiber

30. Explain the difference between a single-mode and a multimode optical fiber.

31. Identify the advantages and disadvantages of each type of optical fiber.

32. Explain the advantages of optical fibers for information transfer.

33. Describe how satellite systems are able to transfer information.

• polar orbit--satellite moves in a close orbit that passed over the Earth's poles.

• geostationary orbit--satellite remains in a distant orbit over a fixed point above the equation

30. Identify the advantages and disadvantages of satellite systems.

Advantage	Disadvantage
widespread coverage	very high initial cost
no right-of-way issues	possible interference
	government regulations require licenses and limit the  use to specific frequencies

30. Global standards for digital electronic products

 

Summative Assessment: Test objectives 1-35