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Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins.
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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.
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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.
- Open236 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.
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Chapter 2
VA rating
Half load, full load and overload on a 12 VA transformer.
- Locked236 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.
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Chapter 3
Center taps
Two halves and two diodes make full-wave DC.
- Locked267 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.
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Chapter 4
Regulation under load
Why a 12 V transformer reads 13 V, and what a brownout adds.
- Locked236 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.
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Chapter 5
Isolation
A floating secondary, and what it does not protect against.
- Locked218 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.
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Chapter 6
24 V control transformers
R, C, W and G, the VA budget, Class 2 and the fuse.
- Locked218 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.
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Chapter 7
Boss project
A 24 VAC control supply with a regulated 12 V rail.
- Locked249 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.
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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.
Turns ratio
- Turns ratio: volts down, amps upTwo coils on one iron core: the turns ratio sets the volts, the amps trade the other way, and DC gets nothing through at all.
VA rating
- VA rating: how much it can giveVolts 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.
Center taps
- Center taps and full-wave DCA tap in the middle of the secondary gives two equal halves: with two diodes, a full-wave rectifier with half the ripple of one.
Regulation under load
- Regulation under loadWhy 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.
Isolation
- Isolation: the secondary floatsNo wire joins the windings, so a floating secondary has no path to earth. What that protects you from, and what it never does.
24 V control transformers
- 24 V control transformersThe 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.
Boss project
- Boss: a 24 VAC control supplyOne 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.
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.