Source: https://mokxi.com/learn/path/transformers-in-practice Updated: 2026-11-11 All paths # Transformers in practice The iron box between the wall and your project, measured: turns ratio, VA ratings, center taps, regulation under load, isolation, and the 24 V control transformer in every furnace. Free 7 lessons 5 h 7 chapters 1,660 XP Electrical ยท Intermediate +150 XP 0 of 7 done Start the course free Turns ratio: volts down, amps up Lesson plan for teachers What you will build ## 0 projects, built step by step 7 lessons in 7 chapters, about 5 hours on a simulated breadboard. Free, in your browser, every step checked by the simulator. The map ## Chapter by chapter Each lesson opens when the one before it is done, and each chapter ends in a project. Chapter 1 ## Turns ratio Volts down, amps up, and why DC gets nothing through. Open 236 XP ### Turns ratio: volts down, amps up Two coils on one iron core: the turns ratio sets the volts, the amps trade the other way, and DC gets nothing through at all. 0 of 6 steps Start What is in it Chapter 2 ## VA rating Half load, full load and overload on a 12 VA transformer. Locked 236 XP ### VA rating: how much it can give Volts times amps is the number on the label. Load a 12 VA transformer to half, to full and past it, and watch the volts sag and the copper heat. 0 of 6 steps Chapter 3 ## Center taps Two halves and two diodes make full-wave DC. Locked 267 XP ### Center taps and full-wave DC A tap in the middle of the secondary gives two equal halves: with two diodes, a full-wave rectifier with half the ripple of one. 0 of 7 steps Chapter 4 ## Regulation under load Why a 12 V transformer reads 13 V, and what a brownout adds. Locked 236 XP ### Regulation under load Why a 12 V transformer reads 13 V on the bench: no-load versus full-load voltage, regulation as a percentage, and what a brownout adds. 0 of 6 steps Chapter 5 ## Isolation A floating secondary, and what it does not protect against. Locked 218 XP ### Isolation: the secondary floats No wire joins the windings, so a floating secondary has no path to earth. What that protects you from, and what it never does. 0 of 6 steps Chapter 6 ## 24 V control transformers R, C, W and G, the VA budget, Class 2 and the fuse. Locked 218 XP ### 24 V control transformers The transformer in every furnace and air handler: R and C, the thermostat's W and G, a VA budget, and the fuse on the secondary. 0 of 6 steps Chapter 7 ## Boss project A 24 VAC control supply with a regulated 12 V rail. Locked 249 XP ### Boss: a 24 VAC control supply One 24 V transformer runs a thermostat loop and a regulated 12 V DC rail: center tap, full-wave, VA budget and regulation in one build you then change. 0 of 7 steps Syllabus ## Every lesson in the course All 7 lessons, in order, each with what it covers. Any of them opens in the editor right away. Chapter 1 ### Turns ratio - Turns ratio: volts down, amps up Two coils on one iron core: the turns ratio sets the volts, the amps trade the other way, and DC gets nothing through at all. Chapter 2 ### VA rating - VA rating: how much it can give Volts times amps is the number on the label. Load a 12 VA transformer to half, to full and past it, and watch the volts sag and the copper heat. Chapter 3 ### Center taps - Center taps and full-wave DC A tap in the middle of the secondary gives two equal halves: with two diodes, a full-wave rectifier with half the ripple of one. Chapter 4 ### Regulation under load - Regulation under load Why a 12 V transformer reads 13 V on the bench: no-load versus full-load voltage, regulation as a percentage, and what a brownout adds. Chapter 5 ### Isolation - Isolation: the secondary floats No wire joins the windings, so a floating secondary has no path to earth. What that protects you from, and what it never does. Chapter 6 ### 24 V control transformers - 24 V control transformers The transformer in every furnace and air handler: R and C, the thermostat's W and G, a VA budget, and the fuse on the secondary. Chapter 7 ### Boss project - Boss: a 24 VAC control supply One 24 V transformer runs a thermostat loop and a regulated 12 V DC rail: center tap, full-wave, VA budget and regulation in one build you then change. Kits ## Build it on your bench too Every lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts. Have a kit already? ### Find your kit Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins. See every kit Questions ## About Transformers in practice Is Transformers in practice free? Yes. All 7 lessons of Transformers in practice are free and run in your browser, with nothing to install and no parts to buy before you start. Do I need any parts? No. Every circuit is built on a simulated breadboard, and the simulator checks each step as you go. When you want to build it for real, the same parts and wiring work on a real bench. How long does Transformers in practice take? About 5 hours: 7 lessons in 7 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off. Where do I start? With "Turns ratio: volts down, amps up", and each lesson builds on the one before it. New to circuits? Electronics basics is the course that starts from zero.