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...
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,...
Build Log
A room monitor that serves its own dashboard: NodeMCU, DHT11 and no cloud account
Most IoT tutorials start by making you an account somewhere, then the free tier changes and your project is landfill. This one has no account and no broker:...
