Basic Electronic Systems

1. Basic Electronic Systems S3 Physics

2. Electronic components Lesson 1 Learning Intentions At the end of lesson 1 you should be able to; • Revise energy change in electrical components. • Identify input and output components. • Distinguish between digital and analogue outputs. • Identify analogue and digital signals from waveforms viewed on an oscilloscope. • Give examples of output devices and describe the energy conversions involved. • Give examples of digital output devices and of analogue output devices. • Draw and identify the symbol for an LED. • State that an LED will light only if connected one way round. • State that different numbers can be produced by lighting appropriate segments of a 7-segment display.

3. Types of Energy • Movement(kinetic) • Atomic(nuclear) • Chemical • Heat • Electrical • Light • Potential • Sound

4. Energy transfer • Energy cannot be created or , only transferred from one form into another. • The energy transfer in a microphone is sound The arrow shows the direction of energy transfer

5. Analogue Electronics In analogue electronics the input and output devices work with a range of voltages. The voltage can be any value and will vary . 1 0

6. Digital Electronics In digital electronics the input and output devices work with two options only: on (1) or off (0). There are no other in digital electronics 1 (on) 0 (off)

7. Input and Output devices • Can you describe the energy transfer that takes place in the input and output devices around the lab and state whether they are analogue or digital? • Fill in the row for each component on worksheet 1. • How about this input device? • http://www.bbc.co.uk/learningzone/clips/touch-screen-technology/818.html

8. LED • Light Emitting Diode. • The LED is a digital output device that will only emit light if it is connected the correct way to a battery or cell.

9. LED • The LED is a digital output device that will only emit light if it connected the correct way to a battery or cell. • A resistor is usually put in series with an LED to ensure it receives the correct values of Voltage and Current.

10. 7 segment display • Usually used to display numbers on digital clocks, watches and . • Named because they have 7 segments that can be lit up individually or in combination to form a display.

11. Numbers on a 7 seg display

12. Input, Process, Output Lesson 2 Learning Intentions At the end of lesson 2 you should be able to; • State that an electronic system consists of three parts and name them. • Give examples of input devices and describe the energy transfer that takes place. • Give examples of digital input devices and analogue input devices.

13. Basic Electronic Systems All practical electronic systems have three distinct parts: INPUT The input to the system detects some form of input, this can be a physical property like light or temperature, or something as simple as a switch. Sources of information such as CD’s and software are also inputs. PROCESS Any electronic system will do something with the information it receives from an input and use it to control an output. This is called the process of the system. OUTPUT Output devices either provide information (displays etc) or perform a useful function such as creating light, heat or sound

14. Input Process Output

15. Public address system Microphone Amplifier Loudspeaker

16. Input – Process - Output • Put each of the following into a table grouping them as either input devices, processes or output devices • Speaker, Light dependant resistor, Temperature dependant resistor, Heater, Microchip, Bulb, Switch, LED, Logic Gates, Motor, 7 segment display, Relay, Transistor. • Now put as many different parts of a computer into a table under the same 3 headings.

17. Input – Process - Output • Try and draw an input-process-output diagram for each of the following: • School tannoy system • Calculator • Bathroom extractor fan • Streetlights • Try to use the proper names for electronic components.

18. Resistive input devices Lesson 3 Learning Intentions At the end of lesson 3 you should be able to; • State how the resistance of a thermistor changes with increasing temperature • State how the resistance of an LDR changes with increasing light intensity.

19. Resistive Input Devices • Your task this period is to design and carry out two simple experiments to answer the two questions below. Write these up fully with aim’s, methods, results etc. • As an LDR is exposed to greater levels of light, will its resistance increase or decrease? • As a thermistor is heated, will its resistance increase or decrease?

20. Resistive Input Devices • LDR (Light Dependant Resistor) An LRD changes resistance when exposed to different strengths of light. When moved from dark to light its resistance _________. • Thermistor (temperature dependant resistor) A thermistor changes resistance when exposed to different temperatures. When the temperature is increased, its resistance __________. decreases decreases

21. LURD • Light • Up • Resistance • Down • TURD • Temperature • Up • Resistance • Down

22. Logic circuits Lesson 4 - 6 Learning Intentions At the end of lesson 6 you should be able to; • Draw and identify the symbols for two input AND and OR gates, and a NOT gate • State that logic gates may have one or more inputs and that a truth table shows the output for all possible input combinations • State that high voltage = logic ‘1’ low voltage = logic ‘0’ • Draw the truth tables for two input AND and OR gates, and a NOT gate • Design circuits that will meet specific requirements

23. Logic Systems Logic systems are often used in system design as they are much easier to understand than full circuit diagrams. They work with digital signals and can be either on or off. Logic level 1 = on Logic level 0= off We use logic gates to achieve a desired output depending on the condition of one or more inputs.

24. Logic Gates There are 3 types of Logic Gate: NOT Gate NOT gates are the simplest gate. They have one input and one output and simply invert the signal AND Gate AND gates have two inputs which must both be at 1 to get a 1 output, otherwise they will give a 0 output. OR Gate OR gates will give a 1 output if either or both of the two inputs are at a 1.

25. Logic Gates There are 3 types of Logic Gate: NOT Gate NOT gates are the simplest gate. They have one input and one output and simply invert the signal AND Gate AND gates have two inputs which must both be at 1 to get a 1 output, otherwise they will give a 0 output. OR Gate OR gates will give a 1 output if either or both of the two inputs are at a 1.

26. A Output B A Output B A B Output C Draw truth tables for the following systems….

27. A Output B A Output B A B Output C Draw truth tables for the following systems….

28. Design Challenges For each of the following, design the system then write the problem and draw a diagram of the solution in your Jotter. • Design a system to sound a buzzer when it gets too cold. • Design a system to light a lamp when a switch is pressed and it is warm. • Add a lamp test switch to Q2 such that the bulb will light either when it is warm AND a switch is pressed, OR if a separate switch is pressed. • Ask the teacher about using an OR gate as a latch. Design a burglar alarm system to sound the buzzer when a thief steps on a pressure pad (switch).

29. A B C Starter Question • Draw a truth table for the following circuit.

30. Switching circuits Lesson 7 - 8 Learning Intentions At the end of lesson 8 you should be able to; • Describe the use of LDR and Thermistor in a potential divider circuit to provide a voltage signal used to control a switching circuit. • State that a transistor can be used as a switch. • State that a transistor may be conducting or non-conducting, ie ON or OFF. • Draw and identify the circuit symbol for an NPN transistor. • Identify from a circuit diagram the purpose of a simple transistor switching circuit.

31. Potential divider circuits Vs Also and more simply known as a resistors in series circuit. Remember, in a series circuit the Current is the same at all points; Is = I1 =I2 The Voltage splits between the resistors; Vs = V1 + V2 A A V1 V2

32. Input Potential divider circuits • In Electronics they are usually shown vertically. • These are often used as control circuits in electronics. • The Voltage across R2 also goes to the transistor and determines whether it will switch on or not. +5V Resistor 1 Resistor 2 0V

33. What is a potential divider circuit? • It is a circuit that has 2 resistors connected in series. • The potential (voltage) splits between the resistors. • We will now use the croc physics program to investigate how the potential splits depending on the size of resistance of the resistors. • Conclusion • The bigger the resistance the bigger the share of the potential.

34. collector base emitter The Transistor A transistor is a voltage operated switch, commonly used to connect an analogue input (such as an LDR) to a digital output (such as an LED). When the voltage at the base reaches about 0.7V, the transistor allows current to flow from the emitter to the collector and switches on.

35. Practical Worksheets • There are 5 stations, and there should be no more than 1 group at any one station at a time. • Have a play with the circuits changing the resistance of the resistors either manually or by the environmental factors (light or temperature). • Carefully observe how the transistor acts in each circuit. • Take any notes and draw any diagrams carefully and neatly in your jotter. • Try to explain why the LED is being turned on and off.

36. Input Process Output Transistor Circuits +5V Protective Resistor Resistor Transistor LED Thermistor 0V Voltage Divider Transistor Light Emitting Diode

37. n Circuit design • Select appropriate input, process and output devices to use in the design and/or building of specific circuits to meet specific requirements. • The video clip link below might give you some ideas to help your problem solving skills. • http://www.bbc.co.uk/learningzone/clips/electronic-systems-and-burglar-alarms/4560.html