Lesson Notes By Weeks and Term v4 - SHS 3
ELECTRONIC COMPONENTS AND CIRCUITS
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ELECTRONIC COMPONENTS AND CIRCUITS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 3
Term: 2nd Term
Week: 14
Grade code: 2.5.2.LI.2
Strand code: 4
Sub-strand code: 2
Content standard code: 2.5.2.CS.1
Indicator code: 2.5.2.LI.2
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRONIC COMPONENTS AND CIRCUITS
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This lesson introduces one of the most versatile and popular Integrated Circuits (ICs) ever made: the 555 Timer. We see the work of timers all around us in Ghana every day – from the rhythmic blinking of traffic lights in Accra, to the beep of a microwave oven in our homes, to the flashing decorative lights on a "trotro" during festive seasons. The 555 timer is a simple, cheap, and reliable electronic "brain" that allows us to control *when* and for *how long* things happen in a circuit. By understanding how to use it, you gain the power to design and build countless useful electronic gadgets and systems.
A. What is an Integrated Circuit (IC)?
An Integrated Circuit, or IC, is a tiny electronic chip that contains a complete electronic circuit with many components like transistors, resistors, and capacitors all built into a small piece of silicon. The 555 Timer is an IC that comes in an 8-pin package. It is called a "timer" because it is excellent at producing precisely timed electrical pulses. B. The 555 Timer IC Pinout
The 555 timer has 8 pins. To use it, we must know what each pin does. Imagine it like a house with 8 doors, each with a specific purpose.
| Pin Number | Name | Function | | :--------- | :---- | :--------------------------------------------------------------------------------- | | 1 | GND | Ground. Connects to the negative terminal (0V) of the power supply. | | 2 | TRIG | Trigger. This pin starts the timing cycle in monostable mode. | | 3 | OUT | Output. This is where the result comes out. It can be HIGH (Vcc) or LOW (0V). | | 4 | RESET | Reset. Used to override other inputs and turn the output OFF (LOW). | | 5 | CTRL | Control Voltage. Allows access to the internal voltage divider (not often used). | | 6 | THRES | Threshold. This pin monitors the capacitor's voltage and ends the timing cycle. | | 7 | DISCH | Discharge. Used to discharge the external timing capacitor. | | 8 | Vcc | Supply Voltage. Connects to the positive terminal of the power supply (+5V to +15V). | C. Modes of Operation