Projects and circuits

Pages about things you can build, grouped by subject. Each page works out its own numbers and links to the lessons behind them.

Microcontrollers and processors

Pinouts, beginner projects and how processors work inside. Each page shows the calculation that decides whether a circuit works, such as LED current or ADC step size.

Computer architectureHow the ARM1 decoded its instructionsWhat microcode is, how the 1985 ARM1 ran each instruction as 1 to 4 rows of a 42-row decode PLA, and why that table is far smaller than 8086 or 68000 microcode.
Microcontrollers8051 microcontroller pin diagram and pin descriptionAll 40 pins of the 8051 (AT89S52, AT89C51) DIP, checked against the Microchip datasheet: ports P0 to P3 and alternate functions, RST, ALE, PSEN, EA, crystal.
Microcontrollers15 Arduino projects for beginners, in the order that teaches the mostFifteen Arduino UNO projects, from a blinking LED to a battery monitor, each with the one calculation that decides if it works: LED current, ADC, PWM, servo.

RF circuits

Small radio circuits you can build on a bench. Each one comes with its coil, capacitor and bias values worked out, and with the legal power limit that applies in India.

RF circuitsFM transmitter circuit: one transistor, every value worked outA 2N3904 Colpitts FM transmitter with coil, tuning, bias and antenna calculated, its real range, and why India allows only 50 nW e.r.p. in 88 to 108 MHz.

Antennas

Home-built antennas with every dimension taken from the wavelength, the most gain each design can give, and India's EIRP limit for 2.4 GHz.

RF circuitsDouble biquad and other DIY Wi-Fi antennas, sized from the wavelengthBiquad, double biquad, tin-can and helix antennas for 2.4 GHz Wi-Fi: dimensions from the wavelength, maximum gain, a link budget and India's 36 dBm EIRP limit.

PCB design

Layout rules for two- and four-layer boards. Each rule comes with its formula, so you can check a trace width or a via yourself.

PCB designHow to design a great PCB: the layout rules, with the numbersPCB layout rules with numbers: IPC-2221 trace width, vias, 50 Ω microstrip on 2 vs 4 layers, decoupling distance and fab limits, each from a cited formula.

Build systems

Complete builds on one page, with the steps in order, fault-finding and a printable card: Arduino festival LED lights and the 555 LED flasher.