Technical Glossary

Know the words before you touch the wires.

You'll encounter these terms in build instructions, and knowing what they mean before you start saves you from Googling mid-solder. This glossary covers every piece of jargon, every acronym, and every physics concept that shows up across the repo — organized by domain so you can skim the section that matters when you're elbow-deep in a build.

For component sourcing, see the Sourcing Guide. For safety implications of anything high-voltage or exothermic, see the Safety docs.

How It All Connects

flowchart LR
    subgraph ⚡ Electrical
        OHM["Ohm's Law"] --> TRANS["Transformer"]
        TRANS --> MOT["MOT"]
        TRANS --> FLY["Flyback"]
        OHM --> MOSFET
        MOSFET --> HBR["H-Bridge"]
        MOSFET --> ESC
        ESC --> BLDC
        RECT["Rectifier"] --> CAPBANK["Cap Bank"]
    end
    subgraph 🧪 Chemistry
        REDOX["Redox"] --> ELYSIS["Electrolysis"]
        ELYSIS --> EPLATE["Electroplating"]
        REDOX --> THERM["Thermite"]
        CAT["Catalyst"] --> EXO["Exothermic"]
    end
    subgraph 🔬 Physics
        LOR["Lorentz Force"] --> MOTORS["Motors"]
        LENZ["Lenz's Law"] --> EDDY["Eddy Current"]
        IND["EM Induction"] --> LENZ
        IND --> TRANS
        RES["Resonance"] --> RUBENS["Rubens' Tube"]
    end
    style OHM fill:#3b82f6,color:#fff
    style REDOX fill:#22c55e,color:#fff
    style IND fill:#a855f7,color:#fff

Electrical & Electronic

The parts that make sparks, spin motors, and occasionally rearrange your day if you're not paying attention.

Term	What It Is	Where You'll See It	Key Builds
MOT (Microwave Oven Transformer)	The heavy iron-core transformer inside every microwave. Takes 120V in, delivers 2000V+ out at lethal current. The most salvaged — and most dangerous — component in this repo. Free at every curb on bulk trash day.	High-voltage builds, plasma projects, spot welders. Any build that needs serious voltage from junk.	#001 Plasma Tornado, #002 Lichtenberg Burner, #034 Jacob's Ladder
Flyback Transformer	The high-voltage transformer from CRT televisions. Low-voltage input, 15-30kV output at low current — enough for plasma arcs and Kirlian photography but slightly less lethal than a MOT. Smaller, lighter, and increasingly rare as CRTs disappear from the wild.	Plasma speakers, Tesla coils, any build that needs thin, crackling arcs instead of thick welding arcs.	#008 Plasma Speaker, #033 Musical Tesla Coil, #196 Kirlian Photography
Capacitor Bank	Multiple capacitors wired in parallel to store a large charge for rapid discharge. A rechargeable battery that dumps all its energy in milliseconds instead of hours. The bigger the bank, the bigger the bang — and the bigger the "do not touch" zone around your workbench.	Electromagnetic launchers, can crushers, plasma igniters — anything that needs a violent burst of current.	#036 Rail Gun, #035 Can Crusher, #275 Plasma Igniter
MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)	A transistor that acts as an electronically controlled switch. A tiny signal from a microcontroller on the gate pin controls a much larger current between drain and source. The workhorse of motor drivers, LED controllers, and anything where a 3.3V brain needs to boss around a 12V load.	Motor control circuits, LED dimming, switching power loads from Arduino/ESP32.	#122 LED Cube, #038 Electromagnetic Levitator, #046 Ferrofluid Mirror
ESC (Electronic Speed Controller)	A circuit board that drives brushless motors by electronically commutating the three-phase windings. Salvaged from dead drones, e-scooters, and RC cars. Without an ESC, a brushless motor is just an expensive paperweight with three mystery wires.	Drone builds, electric vehicles, anything with a BLDC motor that needs to spin at variable speed.	#136 ESP32 Micro Drone, #088 Electric Skateboard, #024 Electric Go-Kart
PWM (Pulse Width Modulation)	A technique for controlling power by rapidly switching a signal on and off. The duty cycle (ratio of on-time to total time) determines effective power. Your microcontroller doesn't actually output variable voltage — it just blinks really, really fast and your motor can't tell the difference.	LED brightness control, motor speed control, servo positioning, heater regulation. Basically everywhere.	#104 Cold Spark Machine, #266 Galvo Laser Show, #243 Heated Gloves
BLDC Motor (Brushless DC)	A motor with permanent magnets on the rotor and electromagnetic coils on the stator — no physical brushes to wear out. Found in drones, e-scooters, hard drives, and computer fans. Spin them backwards and they become generators. Requires an ESC to run.	Electric vehicles, drones, wind turbines, anything that needs efficient rotational power or power generation from salvaged parts.	#204 Wind Turbine, #088 Electric Skateboard, #024 Electric Go-Kart
Galvanometer (Galvo)	A precision motor that tilts a tiny mirror through a small angular range at very high speed. Two galvos (X and Y) steer a laser beam fast enough to draw patterns, text, and animations in the air. Salvaged from laser printers, barcode scanners, and old hard drives.	Laser shows, laser spirographs, laser harps — anything that needs to aim a beam in two dimensions at speed.	#266 Galvo Laser Show, #271 Laser Spirograph, #267 Laser Harp
Piezoelectric Transducer (Piezo Element)	A ceramic disc that converts mechanical stress into voltage (squeeze it, get a spark) or voltage into vibration (apply voltage, get a buzz). Found in buzzers, grill igniters, and cheap lighters. The same physics that ignites your gas stove can also detect vibration or generate ultrasonic frequencies.	Ignition systems, drum triggers, contact microphones, ultrasonic fog machines, shock pranks.	#256 Shock Pen, #237 Bucket Drum Kit, #084 Ultrasonic Fog Machine
PIR Sensor (Passive Infrared)	Detects changes in infrared radiation — i.e., body heat moving through its field of view. The white dome on security lights and automatic doors. Outputs a simple HIGH/LOW signal when motion is detected. Cheap, reliable, and perfect for triggering builds when someone walks by.	Motion-activated pranks, security cameras, automated lighting, jump scare rigs.	#255 Motion Jump Scare, #128 ESP32-CAM Security, #268 Laser Tripwire Alarm
Hall Effect Sensor	A chip that detects magnetic fields. Output changes proportionally to field strength, or switches on/off when a magnet passes by. Used for RPM measurement, position sensing, and current detection. Found in computer fans, brushless motors, and automotive sensors.	POV displays (triggering once per revolution), digital scales, speed/RPM measurement on spinning parts.	#057 HDD POV Clock, #019 POV Globe, #207 Precision Digital Scale
Relay	An electrically controlled mechanical switch. A small current through the coil flips an internal contact, connecting or disconnecting a much larger circuit. The OG of microcontroller power control — when you need an Arduino to switch 120V mains power, a relay does it safely with electrical isolation. Click.	Sequencing multiple high-power loads, mains switching, fireworks ignition, automated watering systems.	#121 Fireworks Sequencer, #103 Smoke Bomb Array, #127 Auto Plant Watering
Solenoid	An electromagnet with a retractable plunger. Apply current, the plunger shoots in or out. Cut the current, a spring pushes it back. Found in sprinkler valves, door locks, vending machines, and car starters. Any build that needs to push, pull, strike, or lock something at the command of a microcontroller.	Pipe organs (valve actuation), firework launchers, coil guns, automated locks.	#236 PVC Pipe Organ, #229 Firework Launcher, #037 Coil Gun
Voice Coil Actuator	A coil of wire sitting in a magnetic field. Push current through the coil, it moves linearly — just like a loudspeaker cone, but repurposed for precision linear motion. Found in hard drives (the read/write arm), CD/DVD drives, and old speakers. Fast, precise, and surprisingly strong for their size.	Hard drive speaker builds, precision positioning, galvo-style mirror actuators, levitation rigs.	#056 Hard Drive Speaker, #038 Electromagnetic Levitator, #057 HDD POV Clock
H-Bridge	A circuit of four switches (transistors or MOSFETs) arranged in an H shape that lets you reverse the polarity of voltage across a motor — spinning it forward or backward. Also enables braking and coasting. The fundamental building block of bidirectional motor control.	Any build with a DC motor that needs to spin both directions: go-karts, robot arms, window motor doors, motorized sliders.	#024 Electric Go-Kart, #183 Hydraulic Robot Arm, #224 Window Motor Secret Door
Ohm's Law (V = IR)	The foundational equation: voltage equals current times resistance. Know any two, calculate the third. This is the first thing you check when a circuit doesn't work. Your 12V power supply driving a 4Ω heating element? That's 3 amps. Ohm's law told you before you plugged it in.	Every single electrical build. Power calculations, resistor selection, wire sizing, fuse ratings. If electrons are involved, Ohm's law applies.	Every electrical build in this repo
Impedance	AC resistance — not just opposition to current flow (resistance), but also opposition from capacitors and inductors that depends on frequency. Measured in ohms but more complex than a simple resistor. Matters whenever you're matching speakers to amplifiers or tuning radio circuits.	Audio builds (speaker matching), radio projects, Tesla coil tuning, antenna design. Anywhere AC signals meet real components.	#169 Vacuum Tube Amp, #134 Pirate Radio
Diode	A one-way valve for electricity. Current flows freely in one direction (forward bias) and is blocked in the other (reverse bias). Found everywhere: power supplies, motor protection, LED circuits. LEDs are literally diodes that emit light — "Light Emitting Diode."	Rectifier circuits, flyback protection on relay/motor coils, LED circuits, voltage regulation.	#067 Laptop Battery Power Bank, #052 DIY Powerwall
Transistor	The fundamental electronic switch/amplifier. A small current or voltage on one pin controls a much larger current between the other two pins. MOSFETs are a type of transistor. Billions of them in every computer chip. In junkyard builds, you'll use discrete ones to switch motors, LEDs, and heaters from a microcontroller signal.	Any build where a microcontroller controls a load too powerful for its GPIO pins — which is most of them.	#033 Musical Tesla Coil, #037 Coil Gun
Rectifier	Converts AC (alternating current) to DC (direct current) using diodes. A single diode gives you half-wave rectification (choppy). Four diodes in a bridge give you full-wave (smooth enough for most builds). Every wall-plug power supply has one. Every MOT charging circuit needs one.	Power supply builds, capacitor bank charging circuits, any build that converts mains AC to usable DC.	#275 Capacitor Bank Plasma Igniter, #049 Campfire Thermoelectric Charger
Transformer (general)	Two coils of wire sharing a magnetic core. AC current in one coil induces AC current in the other. The ratio of turns between coils determines the voltage ratio — more turns on the output = step-up, fewer = step-down. MOTs and flyback transformers are specific types. The reason your phone charger doesn't electrocute you.	Any build that changes voltage levels. Power supplies, high-voltage projects, neon signs, Tesla coils.	#166 DIY Neon Sign, #034 Jacob's Ladder

Chemical & Materials

The stuff in jars that makes things glow, burn, crystallize, dissolve, and occasionally produce results that get the neighbors' attention. See the full Chemicals Guide for sourcing and safety details.

Term	What It Is	Where You'll See It	Key Builds
KNO3 (Potassium Nitrate)	An oxidizer that provides the oxygen for combustion reactions. Mixed with sugar, it makes smoke bomb composition. Sold as "stump remover" at hardware stores (Spectracide brand). The single most-used chemical in the pyro builds.	Smoke bombs, flame jets, any pyrotechnic composition that needs an oxidizer.	#103 Smoke Bomb Array, #231 KNO3 Flame Jet, #327 Sugar Smoke Bombs
Ferrofluid	A colloidal suspension of iron nanoparticles in a carrier oil. Looks like normal black oil until you bring a magnet close — then it erupts into spectacular spiky hedgehog shapes that follow magnetic field lines. Make it from toner powder and vegetable oil, or buy it. Stains everything it touches. Forever.	Electromagnetic art installations, audio-reactive displays, tornado builds. Anywhere magnets meet liquid for dramatic visual effect.	#046 Ferrofluid Mirror, #011 Ferrofluid Speaker, #053 Singing Ferrofluid Tornado
Thermite	A mixture of aluminum powder and iron oxide (rust) that burns at 4000F+ in an extremely exothermic reaction, producing molten iron. Cannot be extinguished with water — water makes it worse (steam explosion). Used professionally for welding railroad tracks. Used in this repo for melting through things with proper safety protocol. Respect this one.	Dedicated thermite builds only. This doesn't show up casually in other projects.	#105 Thermite Flower Pot, #278 Thermite Sparkler Bombs, #230 Thermite Cold Spark Fountain
Luminol	An organic compound that emits blue chemiluminescent light when it reacts with an oxidizer in the presence of a catalyst (like the iron in blood). Famous from crime dramas. Mix it with hydrogen peroxide and spray it in a dark room for an unforgettable forensic or Halloween effect.	Crime scene simulations, chemiluminescent displays, fog-based murder mystery builds.	#109 Luminol Crime Scene, #233 Luminol Fog Murder Mystery, #111 Chemiluminescent Fountain
Ferric Chloride (FeCl3)	An acidic iron salt solution used to etch copper. Submerge a copper-clad board with a resist pattern, and it dissolves all the exposed copper, leaving your circuit traces behind. The standard DIY method for making PCBs at home. Stains skin yellow-brown and eats through metal — nitrile gloves mandatory.	PCB fabrication, electrochemical etching, any build where you're making a custom circuit board instead of using a breadboard.	#158 PCB Etching Station, #162 Electrochemical Etching
Sodium Silicate (Water Glass)	Liquid glass — literally dissolved SiO2 in water. Drop metal salt crystals into it and they grow into bizarre, branching "chemical gardens" overnight. Also used as a fireproofing treatment, adhesive, and egg preservative (seriously). Buy it from chemical suppliers or make it by dissolving silica gel in lye.	Chemical garden demonstrations, fireproofing treatments, pH-reactive art projects.	#164 Sodium Silicate Demos, #163 pH-Reactive Paint
Fluorescein	A fluorescent dye that glows bright green under UV or blue light. Non-toxic in dilute solution — plumbers use it to find leaks. A tiny amount turns an entire fountain, pool, or water wall into a glowing neon display. A little goes an absurdly long way: one gram can visibly color 500 liters.	UV-reactive water features, blacklight fountains, any build that needs water to glow an unnatural shade of green.	#118 Fluorescein Blacklight Fountain, #023 UV-Reactive Water Wall
Nichrome Wire	A nickel-chromium alloy wire with high electrical resistance. Pass current through it and it glows red-hot. Found in toasters, hair dryers, space heaters, and vape coils. Used as heating elements, pyrotechnic igniters, and hot-wire foam cutters.	Heated clothing, ignition systems for pyro builds, atmospheric reentry simulators, anything that needs a controlled source of heat from a wire.	#103 Smoke Bomb Array, #243 Heated Gloves, #006 Atmospheric Reentry Simulator
Peltier Module / TEC (Thermoelectric Cooler)	A flat ceramic tile that gets hot on one side and cold on the other when you apply DC voltage. Flip the polarity and the hot/cold sides swap. Based on the Peltier effect — current through dissimilar semiconductor junctions creates a temperature differential. Salvaged from mini-fridges and water coolers.	Portable coolers, cloud chambers (cooling the chamber floor), thermoelectric generators that convert heat differentials back into electricity.	#096 Peltier Portable Cooler, #041 Cloud Chamber, #049 Campfire Thermoelectric Charger
Strontium Aluminate	The glow-in-the-dark powder that actually works. Absorbs light energy and re-emits it for hours (not the pathetic minutes you get from old zinc sulfide). Mixed into resin, paint, or epoxy for long-lasting luminescence. Green and aqua glow brightest; red and purple are dimmer but more dramatic.	Glow-in-the-dark resin pours, light painting, luminescent coatings on finished builds.	#117 Glow Resin River Table, #178 Light Painting Robot
Calcium Carbide (CaC2)	Gray rocky chunks that react violently with water to produce acetylene gas — extremely flammable, burns with a bright white flame. Same gas used in welding torches. Drop it in water, capture the gas, ignite it. The chemistry behind carbide cannons and some truly spectacular flame effects.	Carbide cannons, repeating spark plug igniters, any build that generates flammable gas from a solid-liquid reaction.	#116 Calcium Carbide Cannon, #232 Carbide Spark Plug Repeater, #223 Spark Plug Cannon
Copper Sulfate (CuSO4)	Bright blue crystalline salt. Dissolve it in water and you get a vivid blue solution perfect for growing large, gem-quality crystals, copper electroplating, and PCB etching (as an alternative to ferric chloride). Sold as root killer at hardware stores. Beautiful but toxic — don't drink the blue Kool-Aid.	Crystal growing, electroplating, copper plating with vinegar, PCB etching.	#161 Copper Crystal Tree, #156 Electroplating Station, #328 Copper Plating with Vinegar
Epoxy Resin	A two-part polymer (resin + hardener) that cures into a clear, hard, waterproof solid. Used to encapsulate electronics, make river tables, cast molds, and permanently embed components in a glossy transparent block. Cures exothermically — pour it too thick and it'll cook itself.	Resin art, waterproofing electronics, casting glow powder into furniture, encapsulating CPU jewelry.	#117 Glow Resin River Table, #059 CPU Resin Jewelry, #160 Electroforming Art
Oxidation-Reduction (Redox)	Electron transfer reactions — the chemistry behind rust, fire, batteries, and electroplating. One substance loses electrons (gets oxidized), another gains them (gets reduced). Thermite is a violent redox reaction. A battery is a controlled one. Corrosion is a slow, annoying one.	Thermite, electroplating, batteries, rust removal, fire — any build where chemistry involves electron transfer.	#105 Thermite Flower Pot, #156 Electroplating Station, #212 Electrolysis Rust Eraser
Exothermic / Endothermic	Exothermic reactions release heat (thermite, combustion, mixing concrete). Endothermic reactions absorb heat (instant cold packs, some crystallization processes). Knowing which one you're dealing with tells you whether to expect your beaker to get hot or cold — and whether "hot" means "warm" or "4000°F."	Thermite builds (violently exothermic), cold packs, crystallization, any chemistry build where temperature matters.	#105 Thermite Flower Pot, #108 Instant Ice Sculpture
Catalyst	A substance that speeds up a chemical reaction without being consumed by it. Manganese dioxide turns slow hydrogen peroxide decomposition into explosive elephant toothpaste. Platinum catalyzes fuel cell reactions. Iron in blood catalyzes the luminol glow. Small amounts, dramatic effects.	Elephant toothpaste, luminol demonstrations, any build where a reaction needs a kick-start.	#102 Elephant Toothpaste, #109 Luminol Crime Scene
pH	A scale from 0 (battery acid) to 14 (drain cleaner) measuring how acidic or basic a solution is. 7 is neutral. Matters for etching (acidic), electroplating (controlled pH), crystal growing (affects crystal shape), and safety (strong acids and bases both cause chemical burns). A $5 pH meter or litmus paper is all you need.	Etching solutions, electroplating baths, crystal growing, pH-reactive art, chemical safety assessment.	#158 PCB Etching Station, #163 pH-Reactive Paint
Electrolysis	Using electricity to force a chemical reaction that wouldn't happen on its own. Two electrodes in a solution, DC current flows, and chemistry happens at each electrode. This is how electroplating deposits metal, how hydrogen generators split water, and how rust erasers clean old tools. The builds practically run themselves once you set up the circuit.	Electroplating, rust removal, hydrogen generation, anodizing, copper plating — any build where DC current drives chemistry in a liquid.	#156 Electroplating Station, #159 Hydrogen Generator, #212 Electrolysis Rust Eraser

Physics Concepts

The principles behind the builds. You don't need to derive the equations, but knowing these concepts will tell you why things work — and why they sometimes don't.

Term	What It Is	Where You'll See It	Key Builds
Lenz's Law	When a magnetic field changes near a conductor, the conductor generates its own opposing magnetic field. This is why a strong magnet falls in slow motion through a copper tube — the tube fights back. Nature hates change, and Lenz's law is the mathematical proof.	Eddy current brakes, slow-motion magnet demonstrations, electromagnetic can crushers, any build that exploits the conductor-vs-magnet fight.	#199 Lenz's Law Slow-Mo Magnet, #186 Eddy Current Brake
Lorentz Force	The force that acts on a current-carrying conductor sitting in a magnetic field. Direction is perpendicular to both the current and the field (right-hand rule). This is the operating principle behind every electric motor ever made. Current + magnets = motion.	Homopolar motors, rail guns, ball bearing motors, coil guns — anything that converts current-in-a-magnetic-field into motion.	#198 Homopolar Motor, #036 Rail Gun, #187 Ball Bearing Motor
Eddy Current	Circular electrical currents induced inside a conductor when it's exposed to a changing magnetic field. The conductor becomes a temporary electromagnet that opposes the change. Responsible for Lenz's law braking, induction heating, and metal detectors.	Electromagnetic brakes, can crushers, metal detectors, induction heater builds.	#186 Eddy Current Brake, #199 Lenz's Law Slow-Mo Magnet, #035 Can Crusher
Lissajous Curve	The pattern you get when you combine two oscillations at different frequencies and/or phases. On an oscilloscope, it draws loops and figure-eights. In laser shows, it produces the mesmerizing geometric patterns that make people stare with their mouths open. The math behind every spirograph.	Laser spirographs, galvo laser shows, CRT oscilloscope visualizers — anything that draws patterns by combining two periodic motions.	#271 Laser Spirograph, #266 Galvo Laser Show, #021 CRT Oscilloscope Visualizer
PID Controller (Proportional-Integral-Derivative)	An algorithm that continuously adjusts an output to maintain a target setpoint. "P" reacts to current error, "I" compensates for accumulated past error, "D" anticipates future error. The most useful three letters in control theory. Once you understand PID, you'll see it everywhere — thermostats, cruise control, drone stabilization.	Temperature regulation (sous vide, reflow oven), electromagnetic levitation, motor speed control, self-balancing builds.	#038 Electromagnetic Levitator, #225 Seat Heater Sous Vide, #260 Toaster Reflow Oven
Curie Temperature	The temperature at which a ferromagnetic material loses its magnetism. Heat a magnet past its Curie point and it becomes non-magnetic. Cool it back down and the magnetism returns. This on/off behavior is the entire operating principle of the Curie engine — a heat engine with no moving parts except the rotor.	Curie engines, Stirling engines (related thermal concepts), any build that exploits the relationship between heat and magnetism.	#189 Curie Engine, #182 Stirling Engine
Persistence of Vision (POV)	Your retina holds onto an image for about 1/25th of a second after the light source disappears. Spin an LED strip fast enough and your brain fills in the gaps, perceiving a solid image floating in space. Your eyes are lying to you, and the builds take full advantage.	POV clocks, POV globes, holographic fan displays, laser shows — any build that exploits your retina's refresh rate.	#057 HDD POV Clock, #019 POV Globe, #022 Holographic Fan Display
Nucleation	The process where dissolved gas or a crystallizing substance needs a surface irregularity (a scratch, a dust particle, a seed crystal) to begin forming bubbles or crystals. Mentos in Diet Coke works because the candy's rough surface provides thousands of nucleation sites. The same principle governs crystal growing and supercooled water.	Supercooled water demonstrations, crystal growing (Rochelle salt, bismuth, copper sulfate), carbonation-based builds.	#170 Supercooled Water, #165 Rochelle Salt Crystal, #107 Bismuth Crystal Garden
Capillary Action	The tendency of a liquid to flow through narrow spaces without (or against) gravity, driven by surface tension and adhesion to the channel walls. Water climbs paper towels, oil wicks up a string, solder flows into a joint. Understanding it explains why some things wick and others don't.	Oil lamp wicks, solder flow in joints, paper-based chromatography, water transport in plant watering systems.	#127 Auto Plant Watering, #248 Solar Still
Faraday Cage	A continuous enclosure of conductive material that blocks external electromagnetic fields. Radio waves, WiFi, cell signals — they all stop at the cage walls. Named after Michael Faraday, who proved the concept in 1836.	EMI shielding for sensitive electronics, EMP protection, RF isolation for radio builds, dramatic demonstrations of electrical safety.	#252 Faraday Cage, #200 DIY Electron Microscope
Electromagnetic Induction	A changing magnetic field creates voltage in a nearby conductor. Move a magnet through a coil of wire and current flows. This single principle explains generators, transformers, induction heaters, and wireless charging. Discovered by Faraday in 1831 — still powering civilization.	Generators (bicycle, wind turbine), transformers, induction heaters, wireless chargers, any build that converts between magnetic fields and electric current.	#050 Bicycle Generator, #204 Wind Turbine
Resonance	When a driving frequency matches a system's natural frequency, energy transfer is maximized and amplitude explodes. A singer shattering a wine glass. A child pumping a swing at just the right moment. A Rubens' tube showing standing waves in flame. Resonance is why some frequencies make things vibrate violently and others don't.	Rubens' tubes (acoustic resonance), Tesla coils (electrical resonance), crystal radios, ultrasonic levitators — anywhere frequency matching matters.	#009 Rubens' Tube, #010 Ultrasonic Levitator, #033 Musical Tesla Coil
Torque	Rotational force — how hard something twists. A wiper motor has high torque (twists hard, turns slowly). A vacuum motor has low torque (spins fast, not much twisting force). Gears trade speed for torque and vice versa. When a motor stalls under load, it ran out of torque, not speed.	Motor selection for builds (matching torque requirements), gear ratios, electric vehicles, robotic arms, any build with spinning parts.	#222 Wiper Motor Rotisserie, #221 Starter Motor Go-Kart, #183 Hydraulic Robot Arm
Mechanical Advantage	Using geometry to multiply force at the expense of distance. Levers, pulleys, gears, and hydraulics all trade movement distance for force multiplication. A trebuchet uses a lever arm. A hydraulic robot arm uses Pascal's principle. A worm gear on a wiper motor is self-locking because the mechanical advantage only works one way.	Trebuchets, hydraulic arms, gear trains, winches, any build that needs more force than the motor alone can provide.	#185 Trebuchet, #183 Hydraulic Robot Arm, #090 Electric Winch
Centripetal Force	The inward force that keeps an object moving in a circle. Without it, the object flies off in a straight line. POV displays work because LEDs spin fast enough that centripetal force keeps them on the right path while persistence of vision fills in the image. Centrifuges use it to separate liquids by density.	POV displays, centrifuges, any build with rapidly spinning parts where circular motion matters.	#057 HDD POV Clock, #019 POV Globe

Builder Fundamentals

The workshop knowledge that separates "following instructions" from "understanding what you're doing." These aren't exotic physics — they're the everyday skills and concepts you'll use on every build.

Term	What It Is	Where You'll See It	Key Builds
Through-Hole vs SMD	Two ways components mount to circuit boards. Through-hole parts have wire legs that poke through holes in the PCB — easy to hand-solder, beginner-friendly. SMD (Surface Mount Device) parts are tiny rectangles soldered flat to pads — smaller, cheaper, but nearly impossible without a reflow oven or hot air station. Salvaged boards have both.	PCB builds, component harvesting from e-waste, reflow oven builds. Understanding this tells you which salvaged components you can actually reuse by hand.	#260 Toaster Reflow Oven, #158 PCB Etching Station
Breadboard	A solderless prototyping board with spring-loaded contacts arranged in rows. Push component legs and jumper wires into the holes and they're electrically connected — no soldering, no permanence. The place where circuits are born, tested, cursed at, and eventually either committed to a PCB or abandoned. Every electronics beginner's first purchase after a microcontroller.	Every beginner electronics build. Prototyping circuits before committing to solder. Testing salvaged components.	#122 LED Cube 8x8x8, #132 ESP32 Weather Station, #133 Arduino Breathalyzer
Flux	A chemical cleaning agent used during soldering. It removes the oxide layer from metal surfaces so molten solder can bond properly. Without flux, solder beads up and refuses to stick. Rosin flux is built into the core of most solder wire (that's what the smoke is when you solder). Separate flux paste or liquid is used for trickier joints and SMD rework.	Every soldering operation. If your solder joints look dull, grainy, or refuse to flow — you need more flux.	Every build that involves soldering

Platforms & Components

The brains and the bling. For pinouts, programming guides, and sensor compatibility, see the full Electronics & Microcontrollers Guide.

Term	What It Is	Where You'll See It	Key Builds
ESP32	A dual-core WiFi + Bluetooth microcontroller that costs $3-5 on AliExpress. Programs with the Arduino IDE or MicroPython. Built-in WiFi for IoT, Bluetooth for wireless control, and enough GPIO pins for most projects. The go-to brain for any build that needs wireless on a junkyard budget.	IoT builds, wireless control, mesh networking, security cameras, weather stations, drones — anything that benefits from WiFi or Bluetooth without adding a separate module.	#125 ESP32 Mesh Walkie-Talkie, #128 ESP32-CAM Security, #136 ESP32 Micro Drone
Arduino	An open-source microcontroller board that runs one program in a loop. No OS, no multitasking — just read sensors, make decisions, control outputs, repeat. Dead simple to program (C++), mountains of tutorials online, and clone boards cost $3-5. The gateway drug to electronics.	Every beginner electronics build. LED cubes, guitar pedals, stepper motor control, sensor projects. If it's your first microcontroller project, start here.	#122 LED Cube 8x8x8, #124 Arduino Guitar Pedal, #135 MIDI Stepper Organ
Raspberry Pi	A full Linux computer the size of a credit card. Runs Python, has a desktop GUI, browses the web, and connects to cameras and displays. When a build needs image processing, audio analysis, a web interface, or an actual operating system — this is what you reach for. Overkill for blinking an LED; perfect for face-tracking a laser.	Smart mirrors, pirate radio, ad blockers, face tracking, DJ controllers — anything that needs an OS, a camera, or real computing power.	#123 Smart Mirror, #134 Pirate Radio, #139 Pi-Hole Ad Blocker
WS2812B / Neopixel	Individually addressable RGB LED strips. One data wire from your microcontroller controls hundreds of LEDs independently — each pixel gets its own color and brightness. No separate R/G/B channels, no shift registers, no multiplexing headaches. Just chain them and send pixel data. The standard for every LED build.	LED jackets, LED masks, infinity mirrors, POV displays, ambient lighting — any build that needs colorful, programmable light.	#242 LED Jacket, #244 LED Mask, #016 Infinity Mirror Table
ILDA (International Laser Display Association Standard)	The standardized connector and signal format for laser show equipment. An ILDA cable carries X/Y position signals (for galvos) plus color modulation signals (for the laser), all as analog voltages. If you're building a laser show that needs to talk to professional galvo scanners, ILDA is the interface language.	Galvo laser shows, laser spirographs, any build that interfaces with professional-grade laser projection hardware.	#266 Galvo Laser Show, #271 Laser Spirograph