Free · No sign-up
Knowledge Base
15 articles on the parts, the arithmetic, the bench technique and the builds a project actually needs. Written to be read on a phone with a component in your other hand — not scanned textbook pages.
ShareWhatsApp
Board
15 articles · page 1 of 2
- ArduinoRelay modules: switching a real load from an ArduinoActive low, NO and NC, the JD-VCC jumper, contact ratings that are not what the board says — and how to switch mains without hurting anybody.8 min read
- Arduino16x2 LCD with I2C, on ArduinoFour wires instead of twelve: finding the address, the contrast trimmer that makes a blank screen look broken, and printing values that do not leave debris behind.7 min read
- ArduinoDHT11 and DHT22 temperature and humidity, on ArduinoWire either sensor to an Arduino, read temperature and humidity over serial, and know which of the two to buy — they are not interchangeable.5 min read
- ArduinoHC-SR04 ultrasonic distance sensor, on ArduinoMeasure distance with sound: the wiring, the timing, the arithmetic that turns microseconds into centimetres, and the surfaces it cannot see.5 min read
- ArduinoPIR motion sensor, on ArduinoDetect a person walking past with an HC-SR501: the two trimmers nobody explains, why it needs a warm-up, and what it actually senses.5 min read
- ComponentsResistor colour codeRead any 4, 5 or 6 band resistor: the digit, multiplier and tolerance tables, which end to start from, and the SMD codes.7 min read
- ComponentsCapacitor codes and markingsWhat 104, 22p and 10uF 25V actually mean, the tolerance and dielectric letters, and which way round a polarised capacitor goes.6 min read
- ComponentsLEDs and the series resistorWhy an LED needs a resistor, how to calculate it for any supply voltage, forward voltages by colour, and the mistakes that kill LEDs and microcontroller pins.6 min read
- Circuits and theoryOhm's law and powerV = I R and P = V I, with the series and parallel rules, the voltage divider, and how to pick a resistor that will not cook.5 min read
- Circuits and theoryThe 555 timer: astable and monostableThe pin-out, both standard circuits with their formulas worked through, how to choose R and C, and the four wiring mistakes that stop a 555 oscillating.7 min read
- Circuits and theoryLogic gates and truth tablesAll seven gates with their truth tables and symbols, why NAND builds everything, De Morgan's theorem, and the wiring rules for real 74-series chips.6 min read
- At the benchSoldering, properlyWhat flux is for, the five-second method that makes a good joint, how to read a bad one, and how to remove a part without lifting the pad.7 min read
Something missing?
Tell us the topic you were looking for and could not find. The list above grows from what students actually ask, and the questions that come in more than twice get written up next.
Written here, not collected from elsewhere. Share it with your class — it is free and there is nothing to sign up for.