Transcript Presented by Tim Surtell and Allan Wilkins in association with

IN
LECTRONICS
E
MECCANO
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!
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O
s
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n
Ha
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