Bhargava's EV&RE Level 001 Report

11 / 10 / 2026

Marvel - Task

Task 01 - LTspice and KiCad

Objective: Design and simulate a 555 timer-based astable multivibrator using LTspice to observe the frequency and pulse-width behavior. Create the circuit schematic in KiCad, assign footprints, and design a PCB layout with proper routing.

Outcomes and Learnings: I designed and simulated a 555 timer astable multivibrator in LTspice and learned how the resistor and capacitor values set the output frequency and duty cycle. In KiCad, I created the schematic, assigned footprints, passed the Electrical Rules Check (ERC), and completed the PCB layout, which passed the Design Rules Check (DRC). The circuit uses an NE555P timer IC, 1 kΩ and 10 kΩ resistors, a 10 µF polarized capacitor and a 10 nF capacitor.

Task 02 - Point Turn of a Vehicle with Ultrasonic Sensor (Embedded)

Objective: Build an obstacle-avoiding robot using an HC-SR04 ultrasonic sensor, Arduino Uno and a motor driver. The vehicle detects obstacles and performs a point turn to change direction.

Outcomes and Learnings: I built the vehicle with an Arduino Uno, HC-SR04 sensor, L298N motor driver and two DC motors. The Arduino measured the echo pulse width and converted it to centimetres. When an obstacle came within the 20 cm threshold, it stopped the motors and turned one wheel forward and the other backward to rotate in place, then resumed moving forward.

I learned how ultrasonic ranging works, how pulseIn() with a timeout avoids hangs, and how an H-bridge and PWM control motor direction and speed. The sense, decide and act loop is the basis of autonomous robots.

Task 03 - Temperature and Humidity Detection (Embedded)

Objective: Use an LM35 analog temperature sensor to switch an LED through a BJT when the temperature exceeds a threshold, and use a DHT11 digital sensor to show temperature and humidity on a 16×2 LCD.

Outcomes and Learnings: The LM35 reading drove a BJT transistor that turned the LED on above the preset threshold. The DHT11 values were shown in real time on the 16×2 LCD. The project showed the difference between analog and digital sensors and the basics of LCD and sensor interfacing.

Task 05 - Battery Capacity Measurement (Power Electronics)

Objective: Monitor a Li-ion battery voltage with an Arduino and use a MOSFET switch to disconnect the load when the voltage drops below a safe threshold.

Outcomes and Learnings: In Tinkercad, I built the circuit with an Arduino Uno, an N-channel MOSFET, an LED load, a 9 V battery and resistors. A voltage divider scaled the battery voltage into the 0 to 5 V ADC range on pin A0, and the Arduino converted the reading back to real volts. When the voltage fell below the threshold, the Arduino turned the MOSFET off and disconnected the load. I confirmed this by lowering the battery voltage and watching the Serial Monitor until the LED switched off.

I learned how a voltage divider scales a signal for an ADC, and why a hysteresis margin prevents flickering near the cutoff. Li-ion cells should not be discharged below about 3.0 to 3.2 V.

Task 06 - Battery Charging (Power Electronics)

Objective: Understand solar-based charging of a Li-ion battery using a solar panel, a charge controller and the CC/CV charging method.

Outcomes and Learnings: I studied a solar charger for an 18650 cell built from a solar panel, a TP4056 charging module and a battery holder. The module stops charging at 4.2 V and shows the charging and full states with indicator LEDs.

Because Tinkercad has no solar panel or TP4056, I built a charging simulation with an Arduino Uno, a 5 V supply as the solar source, a 1N4007 blocking diode, a 1 kΩ resistor and a 1000 µF capacitor standing in for the battery. The Arduino read the voltage on A0, turned on a red LED while charging and switched to a green LED at about 4.2 V. The simulation only models the charge: unlike a TP4056, the Arduino indicates the full state but does not stop the charge.

I learned why Li-ion cells must not exceed 4.2 V, and the roles of a blocking diode and a current-limiting resistor.

Task 07 - Solar Tracker (Embedded)

Objective: Use two LDRs and a servo motor, controlled by an Arduino, to orient a solar panel toward the strongest light.

Outcomes and Learnings: In Tinkercad, I built the tracker with an Arduino Uno, two LDRs with 10 kΩ resistors as voltage dividers on A0 and A1, and a micro servo. The Arduino compared the two readings and moved the servo toward the brighter side in 1° steps, limited to 0° to 180°. A dead zone stopped the servo from jittering when the readings were nearly equal. I tested it by changing the light on each LDR and watching the servo turn and stop when the readings balanced.

I learned how an LDR's resistance changes with light and how comparison logic sets the direction of movement.

Task 10 - Auto Night Lamp Using LED for Electric Vehicles (Embedded)

Objective: Build an automatic night lamp that turns an LED on in low light and off in bright light, simulating an automatic headlamp.

Outcomes and Learnings: I built the circuit with an LDR, an NPN BJT, an LED and resistors. In low light the LDR's resistance rises and turns the transistor on, lighting the LED. In bright light the transistor turns off. I tested it with a mobile flashlight to simulate different light levels.

Task 11 - Buck Converter on LTspice (Power Electronics)

Objective: Design and simulate a DC-DC buck converter in LTspice and study its step-down behaviour.

Outcomes and Learnings: The circuit used a MOSFET, a 1N5819 Schottky diode, a 400 µH inductor, a 100 µF capacitor and a 20 Ω load, driven by a PWM source. With a 50 V input, the output settled at about 19.67 V. The inductor current stayed above zero throughout the cycle, so the converter ran in Continuous Conduction Mode (CCM), which gives lower ripple and more stable output.

I learned how PWM sets the output voltage and how the inductor and capacitor smooth the switching.

Task 12 - Wireless Charger Simulation on Tinkercad (Power Electronics)

Objective: Simulate the basic working principle of wireless charging using a transmitter and receiver coil.

Outcomes and Learnings: I built a conceptual wireless-charging circuit in Tinkercad. Tinkercad cannot model real inductive coupling, so the simulation shows the principle rather than measured power transfer.

Task 13 - Utilizing Transistors as Switches and Voltage Regulators (Power Electronics)

Objective: Use an NPN transistor as a digital switch and observe its voltage drop.

Outcomes and Learnings: In Tinkercad, an Arduino Uno drove an NPN transistor base to switch an LED on and off. The transistor introduced a small collector-emitter voltage drop while controlling the load efficiently.

Task 14 - LED Brightness Control Using PWM and MOSFET (Power Electronics)

Objective: Control LED brightness with PWM through an N-channel MOSFET.

Outcomes and Learnings: In Tinkercad, an Arduino Uno sent a PWM signal to a MOSFET gate, with the LED on the drain and the source at ground. Using analogWrite() across duty cycles from 0 to 255, the LED dimmed and brightened as expected. I also saw the PWM waveform on an oscilloscope.

I learned that a gate pull-down resistor keeps the MOSFET off when the pin is idle, and that PWM controls average power efficiently.

Task 15 - AC to DC Conversion and Observing Direct DC vs. Rectified DC (Power Electronics)

Objective: Convert a 50 Hz square-wave signal to DC with a half-wave rectifier and compare it with direct DC.

Outcomes and Learnings: In Tinkercad, an Arduino generated a 50 Hz signal on D9. A 1N4007 diode passed only the positive half-cycle, and a 470 µF capacitor smoothed the output to about 4.3 V, which is the 5 V signal minus the 0.7 V diode drop. An LED on the direct 5 V supply was slightly brighter than one on the filtered output.

The first build made the polarised capacitor burst because I used two Arduino pins as the source. I fixed it by returning the capacitor to GND, and learned that the (+) leg must always be at the higher voltage.

Task 17 - Building a Basic H-Bridge Motor Driver using MOSFETs (Power Electronics)

Objective: Build an H-bridge with N-channel MOSFETs to reverse a DC motor using Arduino signals.

Outcomes and Learnings: I built the driver with four IRF830 MOSFETs, two IR2104 gate drivers, flyback diodes, bootstrap components, a DC motor, a 12 V supply and an Arduino. The IR2104 drivers gave the high-side MOSFETs the gate voltage they need, and their built-in dead time prevents shoot-through. Reversing the inputs reversed the motor, and setting both inputs the same stopped it. The IRF830 is not logic-level and has high on-resistance, so this design suits small motors.