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Transcript
IN LECTRONICS E MECCANO - ! n O s d Han Presented by Tim Surtell in association with Kelsey Park School Electronics Club Computer & Software Services Limited Lecture Outline In this lecture we’ll look at… • • • • The ‘black box’ concept Using the 555 timer IC Three 555 timer circuits Practical matters After the break… • Hands-On session: Build your 555 monostable circuit The ‘Black Box’ of Electronics Power Input(s) Output(s) The Block Diagram Input Process 1 Process 2 Process 3 Output The 555 Timer – A Black Box! 8 2 7 3 4 555 1 6 5 • Eight connections called ‘pins’ • Little white dot and dimple denote pin 1 The 555 Timer – A Black Box! 0V 1 3 4 555 2 8 Vs 7 6 5 • The 555 uses a 3 – 18V DC power supply The 555 Timer – A Black Box! 0V 1 3 Reset 4 555 Trigger 2 8 Vs 7 6 5 • The Trigger and Reset inputs Switches • Connecting a switch to the Trigger input: 1st attempt! Trigger input Switch 0V Switches • Connecting a switch to the Trigger input: 2nd attempt! Vs Trigger input Switch Bang! 0V Switches • Connecting a switch to the Trigger input of the 555 using a pull-up resistor Vs 1kΩ resistor Switch 0V Trigger input The 555 Timer 0V 1 Output 3 Reset 4 • The 555 Output 555 Trigger 2 8 Vs 7 6 5 Lamps • Connecting a lamp to the 555 Output by ‘sourcing’ current Output Lamp 0V Lamps • Connecting a lamp to the 555 Output by ‘sinking’ current Vs Lamp Output Light Emitting Diodes (LEDs) V -2 s R 0.02 Output Resistor R LED 0V Relays Output Vs Motor M Relay Switch Relay Coil 0V 0V Diode The 555 Timer 0V 1 Output 3 Reset 4 555 Trigger 2 8 Vs 7 Discharge 6 Threshold 5 Offset • Connections for the timing components 555 Timer Circuits Three basic circuits… • The bistable • The monostable • The astable Bistable Block Diagram Trigger Input Reset Input 555 Output • The bistable Output is stable in both states, high and low Bistable Timing Diagram Trigger Input Reset Input Output Bistable Triggered Bistable Reset Monostable Block Diagram Timing Components Trigger Input 555 Output • The monostable Output is stable in the low state only • Triggering makes the Output go high for a set length of time Monostable Timing Diagram Trigger Input Output Time period T Monostable Triggered The Timing Components Vs 0V Resistor R T 1.1RC Capacitor C T R 1.1C Astable Block Diagram Timing Components 555 Output • The astable Output is not stable at all. It repeatedly goes high for a set time and then low for a set time Astable Timing Diagram Output Tmark Tspace Tmark Tspace The Timing Components Vs Resistor R1 Resistor R2 Capacitor C 0V The Timing Components T 0.7(R R )C mark 1 2 T 0.7R C space 2 1.44 F (R 2R )C 1 2 Practical Matters Three ways to build circuits… • Breadboard for prototypes • Stripboard to produce final design • Printed Circuit Board (PCB) to produce final design Breadboard Stripboard Printed Circuit Board (PCB) Lecture Summary What you have learned… • How to treat a system as a ‘black box’ with inputs, a process, and outputs • How to break a problem into small blocks • How to use the 555 timer IC inputs and outputs • What the bistable, monostable and astable circuits do • How to test and construct circuits Resistors • Resistance is measured in Ohms (Ω) • Most resistors have four coloured bands Band 1 1st Digit Band 2 2nd Digit Band 3 Multiplier Band 4 Tolerance The Resistor Colour Code Colour Band 1 1st Digit Band 2 2nd Digit Band 3 Multiplier Band 4 Tolerance Black 0 0 x1 Brown 1 1 x 10 1% Red 2 2 x 100 2% Orange 3 3 x 1,000 - Yellow 4 4 x 10,000 - Green 5 5 x 100,000 - Blue 6 6 x 1,000,000 - Violet 7 7 - - Grey 8 8 - - White 9 9 - - Gold - - - 5% Silver - - - 10% - Construction – The Resistors The 1kΩ resistors Brown Black Red 1 0 00 5% Gold Construction – The Resistors Resistors R1 and R2: 1kΩ (brown, black, red, gold) Construction – The Resistors The 820Ω resistor Grey Red 8 2 0 Brown 5% Gold Construction – The Resistors Resistor R3: 820Ω (grey, red, brown, gold) Diodes • Diodes only let current flow through them in one direction 1N4001 Rectifier Diode + - 1N4148 Signal Diode + - Construction – The Diodes Diode D1: 1N4001 (black with grey band) Construction – The Diodes Diodes D2 and D3: 1N4148 (orange with black band) Light Emitting Diodes (LEDs) • Like diodes, current only flows through them in one direction • Three ways of identifying negative lead: • The shortest lead • Largest ‘triangle’ inside the LED • Flat on the LED package - + Construction – The LED LED D4: Green 3mm LED Construction – The 555 Timer IC1: 555 IC Holder IC1 Construction – The Jumper Pins J1 and J2: ‘Smoothing’ and ‘Relay’ jumpers Capacitors Metallised Polyester Capacitors Electrolytic Capacitors (polarised) + Construction – Capacitors Capacitors C1 and C2: 0.01μF (blue) Construction – Capacitors Capacitor C3: 220μF (smallest black) Construction – Capacitors Capacitor C4: 1000μF (largest black) Construction – Variable Resistor Variable Resistor VR1: 100kΩ Construction – Terminal Blocks Terminal Blocks TB1 and TB2 Construction – The Relay Relay RL1 RL1 Time to Power Up! 0V +12V Button M Motor