What’s new

Soldering guide and a high-contrast theme

• Soldering guide: safety first, the tools and temperatures, the five-second joint step by step, and fixing mistakes with braid and a pump. Open it
• Joint inspector: six drawn joints (good, too much, too little, cold, a bridge, a leg that was not heated) to diagnose, each with its cause and fix.
• High contrast: a new setting at the bottom of every page, with pure black and white and stronger colours, borders and focus outlines, in both light and dark themes. It switches on by itself if your device asks for more contrast.

UART, I2C and SPI, bit by bit

• Logic analyser for serial buses: type a message and watch UART send it (start bit, data bits least significant first, parity, stop bit), follow an I2C conversation with a display, a temperature sensor and a missing chip (addresses, ACK and NACK), and read a flash chip’s ID over SPI in any of the four modes. Open it
• Every bit is labelled with who sends it, dotted lines show when the receiver reads, and the decoded bytes are read back from the drawn waveforms.
• Which bus to use, wiring, pull-ups and logic levels, Arduino code for each, and seven new glossary terms.

Motors and H-bridges

• Motors and H-bridges explainer: a clickable H-bridge that shows the current path for forward, reverse, brake and coast, and what happens when two switches on one side short the supply (shoot-through). Open it
• PWM speed control of a small DC motor under different loads, with back-EMF, stall current and why a motor will not start at a low duty cycle.
• Driving motors from an Arduino with a driver chip (truth table and an example sketch), servos and steppers, safety notes, and seven new glossary terms.

Power supplies: regulators, smoothing and batteries

• Power supplies explainer: see where the energy goes in a linear regulator (7805, AMS1117 or MCP1700): output voltage, heat, efficiency and chip temperature, with dropout and overheating explained, and the same job done by a buck converter for comparison. Open it
• From AC to smooth DC: a rectifier and smoothing capacitor, simulated, with the ripple compared against the usual formula and a check that a 7805 after it would still regulate.
• Battery running time for common cells in series and parallel, a guide to choosing a supply, and eight new glossary terms.

Filters and frequency

• Filters and frequency: low-pass, high-pass and band-pass RC filters, one or two stages, with a live circuit diagram, a frequency-response chart (gain in dB on a logarithmic frequency scale) and the input and output waveforms side by side. Open it
• Two new sandbox examples drive a real RC filter at its cutoff frequency: on the oscilloscope the output is 70.7% of the input and 45° behind. Low-pass · High-pass
• Five new glossary terms, including cutoff frequency, decibel and phase.

See your breadboard as a circuit diagram

• Schematic view in the breadboard trainer: whatever you build is drawn as a proper circuit diagram, live, with the voltage on every connection. Open it
• Breadboard mistakes become visible in the diagram: a part with both legs in one strip is drawn “shorted out”, and a leg that goes nowhere ends in an open circle.
• Hover over a line in the diagram to light up its holes on the board, and click a part to select it.

Search the whole site, and a glossary

• Search from any page: the search button at the top, or press / or Ctrl+K. It finds lessons, labs, tools, components, glossary terms and lab sheets, tolerates small typos, and works offline. Search page
• Glossary: plain-English definitions of 74 terms, each linked to where the idea is taught. Open it
• In lessons, glossary terms now have a dotted underline: hover over one or tab to it to see its definition without leaving the page. You can turn this off on the glossary page.

A new home page and navigation

• New navigation: everything is grouped into Learn, Build, Projects, Practise and Teach, with a menu that works on phones too. What’s new and your progress are always one click away.
• New home page: pick a starting point, continue where you left off, explore each area, and see the latest updates.
• Roadmap and My progress now have pages of their own, with filters and a fuller progress summary. Roadmap · My progress
• A complete site map in the footer of every page.

Teacher pack

• Teacher pack: a ten-session course plan, eight printable lab sheets for real practicals (with optional teacher notes), and a class progress summary made from students’ progress codes, decoded privately in the teacher’s browser. Open it
• A “For teachers” link at the bottom of every page.

Digital logic lab: gates, adders, memory and counting

• Circuit lab 05, digital logic: seven gates with live truth tables, building every gate from NAND alone, a 4-bit binary adder, an SR latch and a D flip-flop with timing diagrams, and a 4-bit counter (binary or decade). Open it

Op-amps: amplifiers and comparators, plus an op-amp part

• Op-amps explainer: comparator, voltage follower, non-inverting and inverting amplifiers, with live schematics, the two golden rules, and what happens when the output hits its supply limits. Open it
• An LM358-style dual op-amp in the sandbox and the breadboard trainer, with two breadboard examples (an amplifier and a dark detector) and a new challenge: build an amplifier with a gain of 3.

Check a real build: readings in, likely faults out

• Check a real build: build a breadboard layout for real, type in your multimeter readings, and the trainer suggests what is wrong. Open it
• It simulates every likely single fault (a part open, shorted or in backwards, a wire not making contact, a transistor turned round) and ranks the ones that match your readings, including the effect of the meter itself.

Connect a real Arduino, and a serial monitor

• Hardware lab: connect a real Arduino Uno or Nano to the browser (Chrome or Edge on a computer). Live readings of six analog pins and a button, LED and PWM controls, and recording to a CSV file. Open it
• Five experiments that compare real measurements with the course models: light sensor, thermometer, capacitor charging curve, night light and a 555’s frequency.
• A small, readable bridge sketch to upload once, and a clearly labelled simulated board for trying the page without hardware.
• Serial monitor and plotter for any sketch, with the Arduino IDE’s labelled-value format. Open it
• This page.

Speed drills, printable worksheets and certificates

• Speed drills: timed or untimed rounds of colour codes, unit prefixes and Ohm’s law, with best scores and a retry of missed questions. Open it
• Printable worksheets on ten topics, with sheet codes that always give the same questions and an answer key with working. Open it
• Certificate and progress record, printable, based on your own recorded progress. Open it
• Every page now prints cleanly, without navigation or controls.

Breadboard trainer

• Breadboard trainer: place parts leg by leg on a virtual breadboard; hover over a hole to see everything connected to it.
• Warnings for the classic breadboard mistakes: two legs in one strip, parts not joined across the centre gap, shorts and reversed parts.
• 555 and capacitor circuits run in time; five challenges, examples, share links and a keyboard form. Open it

Oscilloscope, new parts, 555 timer and Blinky

• New sandbox parts: potentiometer, light sensor, thermistor, buzzer, motor, inductor, signal generator and the 555 timer.
• A two-channel oscilloscope with probes, and detection of the voltage spike when an inductor is switched off (with and without a flyback diode).
• Project: 555 Blinky, with a timing calculator, build steps and a link that opens your design in the sandbox. Open it

New home on Netlify

• The site moved to Netlify. A new version only goes live if every automated test passes.

Capacitors and transistors in the sandbox

• Capacitors that charge and discharge in real time, NPN transistors and N-channel MOSFETs in the sandbox, with live readings of each transistor’s state.
• New warnings (missing base resistor, reversed electrolytic, over-voltage), examples and two new challenges.

The circuit sandbox

• Circuit sandbox: build any circuit on a grid and see every voltage and current, solved live, with moving electrons and safety warnings. Open it
• Undo and redo, autosave, share links, a keyboard-friendly editor and build challenges checked on how the circuit behaves.
• Removed the AI help panel, so that learners work problems out for themselves.

Measuring lab, offline use and spaced review

• Circuit lab 03: a virtual multimeter that behaves like a real one, a practice bench and nine find-the-fault circuits. Open it
• Works offline once visited, and can be installed as an app.
• Spaced review: questions you miss come back after 1, 3, 7, 14 and 30 days.
• Progress codes, to move your progress to another browser.

Sensors lab and the night light project

• Circuit lab 02: voltage dividers with a light sensor or thermistor, loading effects and ADC readings. Open it
• Project: automatic night light, simulated from light level to LED brightness, with a matching Arduino sketch. Open it

A full learning site

• The course became a full site: a home page with a learning roadmap and progress saved in your browser.
• Circuit lab 01 (LED and resistor), explainers on the transistor switch and PWM, a component explorer, an embedded-systems lesson and a quick challenge.
• Automated tests for the maths, the content and every page.

The first course

• The first course: eleven animated chapters from “what is electricity?” to logic gates, with a quiz and a cheat sheet. Open the course