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David Smith1 S.G. Electronics Revision Lesson. David Smith2 Introduction Electronic systems have 3 parts Input Process Output There are 2 types of systems:

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Presentation on theme: "David Smith1 S.G. Electronics Revision Lesson. David Smith2 Introduction Electronic systems have 3 parts Input Process Output There are 2 types of systems:"— Presentation transcript:

1 David Smith1 S.G. Electronics Revision Lesson

2 David Smith2 Introduction Electronic systems have 3 parts Input Process Output There are 2 types of systems: Analogue Digital

3 David Smith3 Output Devices These turn EE EE into some other form Analogue Motor, Bulb, Loudspeaker Digital LED, Relay, Solenoid

4 David Smith4 Input Devices 2 main types Change the size of the input voltage Switch, Capacitor, LDR, Thermistor and

5 David Smith5 Input Devices Energy Changers Thermocouple, Microphone Solar Cell

6 David Smith6 LDR As Light Intensity Increases Resistance Decreases

7 David Smith7 Thermistor As Temperature increases the resistance decreases

8 David Smith8 Capacitors Store Charge V –t Provide timing delays

9 David Smith9 Voltage Dividers VsVs 0 V R1R1 R2R2 V out

10 David Smith10 LDR in Voltage Divider As light increases, resistance of LDR decreases, voltage across it decreases, V out

11 David Smith11 Thermistor As temperature decreases, resistance of thermistor increases,voltage across thermistor increases, V out decreases V out

12 David Smith12 Capacitor charges up V out increases V out V s

13 David Smith13 Switches When switch is closed V out is low V out + 5 V

14 David Smith14 Process Devices Analogue : Amplifier Digital : Transistor Logic Gates

15 David Smith15 NPN Transistor V be > 0.7 V Transistor is switched on Collector Base Emitter

16 David Smith16 Alarm Circuits Light Intensity decreases R ldr increases V ldr increases V be increases V be > 0.7 V Transistor switches on Current flows through LED

17 David Smith17 Alarm Circuits Temperature increases R thermistor decreases V thermistor decreases V resistor increases V be increases V be > 0.7 V Transistor switches on Current flows through LED Current flows through LED

18 David Smith18 Capacitor charges up V c increases V be increases V be > 0.7 V transistor switches on Current flows through LED lights up Closing switch discharges capacitor / resets system Alarm Circuits

19 David Smith19 Logic Gates Digital Devices And Gate Or Gate Not Gate

20 David Smith20 And Gate A BOutput

21 David Smith21 Or Gate ABOutput

22 David Smith22 Not Gate InputOutput

23 David Smith23 Clock Pulse Generator Capacitor charges up,V c increases Input to NOT changes from 0 to 1 Output changes to 0, (led on ) Capacitor discharges,V c decreases Input to NOT changes from 1 to 0 Output changes to 1, (led off ) Process repeats

24 David Smith24 Amplifiers Analogue Process Device Frequency unchanged V in V out

25 David Smith25 Amplifiers in CD players amplify power

26 David Smith26 S.G. ELECTRONICS Now try the Revision Questions


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