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Presented by Tim Surtell in association with

Computer & Software Services Limited. Kelsey Park School Electronics Club. Presented by Tim Surtell in association with. 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…

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Presented by Tim Surtell in association with

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  1. Computer & Software Services Limited Kelsey Park School Electronics Club Presented byTim Surtellin association with

  2. 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 Lecture Outline

  3. The ‘Black Box’ of Electronics Power Input(s) Output(s) Process

  4. The Block Diagram Process 1 Process 2 Process 3 Input Output

  5. Eight connections called ‘pins’ The 555 Timer – A Black Box! 555 1 8 2 7 3 6 4 5 • Little white dot and dimple denote pin 1

  6. The 555 uses a 3 – 18V DC power supply The 555 Timer – A Black Box! 0V 1 8 Vs 2 7 6 3 5 4 555

  7. The Trigger and Reset inputs The 555 Timer – A Black Box! 0V 1 8 Vs Trigger 2 7 6 3 5 Reset 4 555

  8. Switches Trigger input Switch 0V • Connecting a switch to the Trigger input: 1st attempt!

  9. Switches Vs Trigger input Switch 0V • Connecting a switch to the Trigger input: 2nd attempt! Bang!

  10. Switches Vs Trigger input 1kΩ resistor Switch 0V • Connecting a switch to the Trigger input of the 555 using a pull-up resistor

  11. The 555 Output The 555 Timer 0V 1 8 Vs Trigger 2 7 6 Output 3 5 Reset 4 555

  12. Lamps Output Lamp 0V • Connecting a lamp to the 555 Output by ‘sourcing’ current

  13. Lamps Vs Output Lamp • Connecting a lamp to the 555 Output by ‘sinking’ current

  14. Light Emitting Diodes (LEDs) Output Resistor R LED 0V

  15. Relays Output Vs Motor M RelaySwitch RelayCoil Diode 0V 0V

  16. Connections for the timing components The 555 Timer 0V 1 8 Vs Trigger 2 7 Discharge 6 Threshold Output 3 5 Offset Reset 4 555

  17. Three basic circuits… The bistable The monostable The astable 555 Timer Circuits

  18. The bistable Output is stable in both states, high and low Bistable Block Diagram Trigger Input 555 Output Reset Input

  19. Bistable Timing Diagram Trigger Input Reset Input Output Bistable Triggered Bistable Reset

  20. The monostable Output is stable in the low state only Triggering makes the Output go high for a set length of time Monostable Block Diagram Timing Components 555 Trigger Input Output

  21. Monostable Timing Diagram Trigger Input Output Time period T Monostable Triggered

  22. The Timing Components Vs Resistor R Capacitor C 0V

  23. The astable Output is not stable at all.It repeatedly goes high for a set time and then low for a set time Astable Block Diagram Timing Components 555 Output

  24. Astable Timing Diagram Output Tmark Tspace Tmark Tspace

  25. The Timing Components Vs Resistor R1 Resistor R2 Capacitor C 0V

  26. The Timing Components

  27. Three ways to build circuits… Breadboard for prototypes Stripboard to produce final design Printed Circuit Board (PCB) to produce final design Practical Matters

  28. Breadboard

  29. Stripboard

  30. Printed Circuit Board (PCB)

  31. 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 Lecture Summary

  32. Resistors Band 1 1st Digit Band 2 2nd Digit Band 3 Multiplier Band 4 Tolerance • Resistance is measured in Ohms (Ω) • Most resistors have four coloured bands

  33. The Resistor Colour Code Colour Band 11st Digit Band 22nd Digit Band 3Multiplier Band 4Tolerance Black 0 0 x 1 - 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%

  34. Construction – The Resistors Brown Black Red Gold 1 0 00 5% The 1kΩ resistors

  35. Construction – The Resistors Resistors R1 and R2: 1kΩ (brown, black, red, gold)

  36. Construction – The Resistors Grey Red Brown Gold 8 2 0 5% The 820Ω resistor

  37. Construction – The Resistors Resistor R3: 820Ω (grey, red, brown, gold)

  38. Diodes 1N4001 Rectifier Diode - + 1N4148 Signal Diode - + • Diodes only let current flow through them in one direction

  39. Construction – The Diodes Diode D1: 1N4001 (black with grey band)

  40. Construction – The Diodes Diodes D2 and D3: 1N4148 (orange with black band)

  41. Light Emitting Diodes (LEDs) • Three ways of identifying negative lead: • The shortest lead • Flat on the LED package - + • Like diodes, current only flows through them in one direction • Largest ‘triangle’ inside the LED

  42. Construction – The LED LED D4: Green 3mm LED

  43. Construction – The 555 Timer IC1: 555 IC Holder

  44. Construction – The Jumper Pins J1 and J2: ‘Smoothing’ and ‘Relay’ jumpers

  45. Capacitors Metallised Polyester Capacitors Electrolytic Capacitors (polarised) - +

  46. Construction – Capacitors Capacitors C1 and C2: 0.01μF (blue)

  47. Construction – Capacitors Capacitor C3: 220μF (smallest black)

  48. Construction – Capacitors Capacitor C4: 1000μF (largest black)

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