# EV-RE Level 1 Report

29 / 3 / 2025

Task 1: Utilizing Transistors as Switches and Voltage Regulators

Using Arduino to Control a Transistor as a Switch

I used an Arduino to understand how transistors can function as switches. The Arduino sends a small signal to the base of the transistor, which activates it, allowing current to flow from the collector to the emitter. As a result, the LED glows.

When the Arduino stops sending the signal to the base, the transistor turns off, preventing current from flowing from the collector to the emitter. Consequently, the LED does not glow.

Using this logic, I implemented a simple LED blinking circuit. The video below demonstrates this process.

Exploring Voltage Regulation Using Transistors

Understanding the Voltage-Drop Phenomenon

I experimented with using transistors to reduce voltage by leveraging the voltage-drop phenomenon. To explore this, I simulated a simple circuit in Tinkercad.

Initially, I connected an LED directly to the battery and measured a voltage of 7.63V. However, after incorporating a transistor into the circuit, the voltage across the LED dropped to approximately 2V.

This experiment helped me realize the role of transistors in voltage regulation and provided insights into the working principle of a buck converter.

Simulation Images

after using transistor :

Task 2: LED Brightness Control Using PWM and an N-Channel MOSFET

Understanding MOSFET Operation and PWM Duty Cycle

In this task, I used an N-channel MOSFET along with an Arduino to control the brightness of an LED. The Arduino sends a voltage signal to the MOSFET's gate, which allows current to flow between the drain and source, completing the circuit and causing the LED to glow. When no signal is sent, the MOSFET remains off, breaking the circuit and preventing the LED from glowing.

To adjust the brightness, I utilized Pulse Width Modulation (PWM). PWM works by rapidly switching the transistor on and off at a certain frequency. The percentage of time the transistor is on in one cycle determines the duty cycle:

• 100% duty cycle → Fully bright LED
• 50% duty cycle → Medium brightness (LED is on for half the time)
• 10% duty cycle → Dim LED (LED is on for a short period in each cycle)

This experiment helped in understanding how MOSFETs function similarly to BJTs as switches but are preferred in certain scenarios due to their efficiency and lower power dissipation.

Video Demonstration

Task 3: AC to DC Conversion and Observing Direct DC vs. Rectified DC

Overview

In this task, I used an Arduino to generate AC-like signals using the PWM technique. However, since the Arduino itself cannot generate pure AC, I simulated AC using pulse width modulation (PWM) by switching a digital pin on and off.

AC to DC Conversion

To convert this simulated AC to DC, I used the half-wave rectification method, where a diode blocks the negative current, and a capacitor filters the output. As a result, the AC signal is converted into rectified DC.

Observations

When I connected an LED to a direct DC source (a battery), it glowed brighter compared to when connected to the rectified DC output.

using direct dc source :

using rectified dc :

Improving Rectified DC Efficiency

Below is a detailed article on how to increase the efficiency of rectified DC and enhance its performance.

Task 4: Generating an AC-Like Signal Using a 555 Timer and MOSFETs

The 555 Timer generates a square wave signal, alternating between HIGH and LOW states. This signal is used to switch two N-channel MOSFETs in a push-pull configuration.

• When the first MOSFET turns ON, it connects the load to ground (0V).
• When the first MOSFET turns OFF, the second MOSFET turns ON, pulling the load HIGH (Vcc).

This alternating switching creates a square wave AC signal, effectively converting DC into an AC-like waveform. The MOSFETs act as power amplifiers, handling higher currents that the 555 Timer alone cannot drive.

in the below image the bulb is broken , which is the proof of amplification :