Electronics and robotics, worked out one circuit at a time: Arduino, sensors, motors, batteries and complete builds, with the diagrams and code for each.
Build a mini sonar radar with an SG90 servo, an HC-SR04 ultrasonic sensor and a 0.96 inch SSD1306 OLED. Wiring, the full sketch that draws range rings, a sweep line and detected objects, and how the polar-to-screen math works.
→ angle + distance → x, y on the screen
How a lab bench power supply works, what CV and CC mode mean, how to set the current limit before connecting a circuit, linear vs switching supplies, the green earth terminal, and how to choose one for a hobby bench.
→ set the current limit with the leads shorted
How a two-wheeled robot can estimate its x, y position and heading from wheel encoder ticks. The odometry equations step by step, Arduino code that updates the pose, how to calibrate wheel size and track width, and why the error grows.
→ calibrate the track width with ten spins
What a BMS board does for a 2S or 3S Li-ion pack, how to wire B−, B1, B2, B+ and P− in the right order, how to choose the current rating, which charger to use, and why a new pack sometimes shows 0 V until it's activated.
→ B− first, then up the pack
How to use the DRV8833 dual motor driver module with Arduino. Pinout, the sleep pin that stops most first attempts, the four control states, fast vs slow decay PWM, and why it beats the L298N for small battery-powered robots.
→ pull nSLEEP high or nothing moves
How the JSN-SR04T waterproof ultrasonic sensor differs from the HC-SR04, its 25 cm blind zone and wide beam, wiring, reliable Arduino code with filtering, and tips for tanks, cars and outdoor projects.
→ nothing closer than 25 cm
How to tell an active buzzer from a passive one, how to wire each to an Arduino safely, and code for beeps, alarm sirens and short melodies with tone(), plus the timer conflict that silently breaks PWM pins.
→ active = DC beep, passive = needs tone()
What a watt is, the three power formulas and when to use each, why resistors and regulators get hot, how to pick a resistor's power rating, and the difference between watts, watt-hours and mAh for batteries.
→ P = V × I, and it all ends up as heat
Build a water tank level indicator with an HC-SR04 ultrasonic sensor, a 16x2 I2C LCD and a buzzer. Shows the level in percent and liters with a bar graph, filters bad readings and sounds a low-level alarm.
→ keep the sensor 5 cm above full water
What flux actually does, the difference between rosin, no-clean and water-soluble flux, when the flux inside your solder isn't enough, how to apply extra flux and how to clean the residue off a board.
→ solder flows where flux has been
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