Lesson Notes By Weeks and Term v4 - SHS 2
DIGITAL ELECTRONICS
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DIGITAL ELECTRONICS
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Subject: Physics
Class: SHS 2
Term: 2nd Term
Week: 13
Grade code: 2.3.3.LI.2
Strand code: 3
Sub-strand code: 3
Content standard code: 2.3.3.CS.1
Indicator code: 2.3.3.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: DIGITAL ELECTRONICS
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In the world of digital electronics, which powers our phones, computers, and even modern traffic lights, information is represented by two simple states: HIGH (1) and LOW (0). However, a major problem arises when an input to a digital circuit is not clearly connected to either HIGH or LOW. This "floating" state is unpredictable and can cause devices to behave erratically. Imagine a light switch that sometimes turns on by itself because of electrical interference—that's the kind of problem a floating input can cause! Today, we will learn about a simple but powerful solution to this problem: using pull-up and pull-down resistors.
Concept 1: Digital Logic Levels and the "Floating" Problem
In digital electronics, we work with binary signals. HIGH (or Logic '1'): Represents a high voltage, typically the supply voltage. We often call this Vcc (e.g., +5V). LOW (or Logic '0'): Represents a low voltage, typically zero volts. We call this Ground (GND).
A digital input pin (like on a microcontroller or a logic gate) needs to read a definite HIGH or LOW to work correctly.
The Problem: What happens if we connect a simple switch to an input pin without anything else?