Lesson Notes By Weeks and Term v4 - SHS 2

Lesson Video

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Performance objectives

• Define pull-up and pull-down resistors and their purpose.
• Differentiate between the two resistor configurations.
• Analyse simple circuits using these resistors.
• Identify real-world applications for this knowledge.

Lesson summary

In the world of digital electronics, which powers our phones, computers, and even modern traffic lights in cities like Accra and Kumasi, we need signals to be clear and definite. A signal must be either HIGH (like a light switch being ON) or LOW (the switch being OFF). But what happens if the switch is in-between, or not properly connected? This creates an uncertain state called a "floating" state, which can cause devices to behave unpredictably. Today, we will learn about two simple but powerful components, pull-up and pull-down resistors, which are used to solve this problem. They act like safety nets, ensuring a digital input always has a default, predictable state.

Lesson notes

A. The Problem: The "Floating" Input Pin

Imagine a digital input pin on a microcontroller (the "brain" of a small electronic device). This pin is designed to read only two states: HIGH (or '1'): A high voltage, typically +5V or +3.3V. LOW (or '0'): A low voltage, typically 0V (Ground or GND).

Now, let's connect a simple push-button switch to this input pin. Our goal is to make the pin read HIGH when the button is pressed and LOW when it is not.

Consider this first attempt at a circuit:

Evaluation guide

• Distinguish between pull up and pull -down resistors.
• Experiential Learning: Using videos or an experimental set up, differentiate between pull up and
• pull-down resistors AND describe their applications.
• conceptual