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Electronics and Control

Technology

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Electronics and Control

The 555 timer is an 8-Pin D.I.L. Integrated Circuit or ‘chip’

What it looks like

Notch

Pin 1

3

Electronics and ControlOperation:•Contains 25 transistors, 2 diodes and 16 resistors

• Maximum operating voltage 16V

• Maximum output current 200mA

If you input certain signals they will be processed / controlled in a certain manner and will produce a known output.

INPUT PROCESS OUTPUT

• Best treated as a single component with required input and output

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Electronics and Control

What the 555 timer is used for:

•To switch on or off an output after a certain time delay i.e.

Games timer, Porch light, Childs mobile, Exercise timer.

•To continually switch on and off an output i.e.

Hazard warning lights, Soft toy, Bicycle indicators.

•As a pulse generator i.e.

To provide a series of clock pulses for a counter.

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Electronics and Control

Digital Terminology:

To use the 555 timer correctly you have to be aware of the correct terminology:

• Monostable Time

• Astable Time

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Electronics and Control

• MONOSTABLE: This is a system which has only one stable state.

It can be made to change but it will always return to its original stable state. A spring operated push button switch is an example of this. Monostable circuits are used as timers and as a single pulse generator.

7Monostable Circuit

Electronics and Control

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Electronics and Control

R1= 33k(Or/Or/Or)

R2= 1k (Br/Bl/Re)

R3= 470(Ye/Vi/Br)

R4= 470(Ye/Vi/Br)

2 No. LEDs

SW1= Toggle Switch

SW2= Tactile Switch

555 IC

3No.Terminal Blocks

Monostable PCB circuit layout:Component list:

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Electronics and Control

• ASTABLE: This is a system which has no stable state. It

changes from one state to the other all the time. A pendulum swings from one side to the other continuously. Astable circuits are used to flash lights or sound a loudspeaker. It can act as a square wave oscillator

10Astable Circuit

Electronics and Control

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Electronics and Control

R1 = 470(Ye/Vi/Br)

R2= 1k (Br/Bl/Re)

R3= 470(Ye/Vi/Br)

VR1= 100K

SW1= Toggle Switch

C1=10uF Capacitor

2 No. LEDs

555 IC

With VR1 set at 68K

flash rate = 1 per sec

Component list: Astable PCB circuit layout:

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Electronics and Control

R1=100 ohmsR2=100 ohmsR3=100 ohmsR4=2200 ohmsR5=1K ohmsVR1=100kC1=10uFQ1=BC 337-16D1=1N4148SW1=Toggle

Components Astable Project Board

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Electronics and Control

Warning signal: 4 LEDS flash simultaneously

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Electronics and Control

Buzzer and 4 LEDs Oscillate ON/OFF – Lorry Reversing

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Electronics and Control

Theme : A Safe Environment

Astable:Hazard / warning lights / school

crossingBicycle indicatorsBurglar AlarmSteep Gradiant IndicatorPersonal Alarm

Monostable:Egg Timer : Food / Electrical safetyBath / Oven Timer