First Builds
Your first working circuit. Start here — nothing assumes you already know.
Arduino
Heart rate monitor: counting beats in a very noisy signal
A finger-clip pulse sensor and the peak detection that turns a wobbly waveform into a BPM number. Why pressing harder makes it worse, why a moving threshold beats...
Arduino
Digital weighing scale: HX711, load cells and the two-point calibration
A scale accurate to a gram or two, and the calibration maths that gets it there. Why a load cell outputs microvolts, why the mounting matters more than...
Arduino
LPG gas leak alarm that you can actually trust
A kitchen gas alarm for about Rs.900. Why the sensor needs 24 hours of burn-in before you believe it, why the datasheet number is not a PPM reading,...
Arduino
Colour-sorting machine: making a TCS3200 tell red from orange
A sensor that reports colour as three frequencies, and the calibration that turns those into an answer. Why the white-balance step is the whole project, why the LEDs...
Beginner
Self-watering planter that texts you when the tank runs dry
Keeps a plant alive while you are away, and tells you before it fails. Why the cheap resistive moisture probes corrode away in weeks, why a dry-run protection...
Arduino
Sound-reactive LED matrix: making a WS2812 panel dance to music
A 16-pixel RGB panel that pulses with whatever is playing, for about Rs.350. Why a sound sensor does not measure loudness the way you expect, the auto-gain trick...
Arduino
Gesture-controlled robot: tilt your hand, the car moves
A glove with a gyroscope on it, a robot 30 metres away, and no lag. Reading tilt from an MPU6050 without the drift everyone complains about, and getting...
Build Log
ESP32-CAM security camera that messages your phone when something moves
A WiFi camera that photographs whatever triggered it and pushes the picture to your phone, for about Rs.850. The brownout that makes people think their board is dead,...
Advanced
Six-servo robotic arm on a PCA9685: power budget, pulse limits and smooth motion
A six-servo arm is where hobby robotics stops being about code and starts being about power. Why 150 and 600 are the wrong pulse counts for your servos,...
