Simple transformer DC pulse circuit - Page 1
Forum section: electronics / beginners

author: maelh
author_rank: Regular Contributor
timestamp: January 13, 2021, 02:29:25 pm
content: Hello,As part of understanding another question I posted here recently, I tried out the simpler circuit in the attachment. (I added blue and red +/- signs to indicate the polarity I assumed in each circuit, after pressing the switch/button.)If the circuit's left LED lights up when pressing the button, it means that the primary and secondary coils are winded in opposite directions, right?Or in other words, the transformer symbol should be with the dots in opposite positions.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 13, 2021, 02:55:01 pm
content: Yes.

author: maelh
author_rank: Regular Contributor
timestamp: January 13, 2021, 03:00:49 pm
content: Is there a special name / shorter name for transformers in this configuration, than just saying "windings in opposite directions"?

author: CaptDon
author_rank: Super Contributor
timestamp: January 13, 2021, 03:11:15 pm
content: And you found when you pressed the button one LED flashed and when you released the button the other LED flashed. Why did it flash and not remain lit.....Because transformers don't transfer D.C., Why did the other one flash on release.....inductive kick.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 13, 2021, 03:20:34 pm
content: There is no preferred orientation, as you could just as well swap the leads around and have it the other way.In discussion, it's usually phrased as in-phase, versus opposing or inverting phase -- assuming one end is grounded so that the distinction makes sense. (Illustrative counter-example: a differential output is both phases, equal and opposite.)Tim

author: maelh
author_rank: Regular Contributor
timestamp: January 13, 2021, 03:27:47 pm
content: Quote from: CaptDon on January 13, 2021, 03:11:15 pmThanks, that part was clear. But I was confused first why it wasn't the right LED when making contact, and the left LED when breaking, because usually transformers are shown as having the same polarity on primary and secondary.And this electronics kit did not explain there is a difference. It's quite vague in general.

author: maelh
author_rank: Regular Contributor
timestamp: January 13, 2021, 03:29:58 pm
content: I found this, regarding terminology:https://www.electricaltechnology.org/2013/12/transformer-phasing-the-dot-notation-and-dot-convention.htmlhttps://circuitdigest.com/article/understanding-dot-convention-in-transformersOther terminology seems to be polarity marking and positive coupling (same polarity) or negative coupling (opposite polarity):https://www.allaboutcircuits.com/textbook/alternating-current/chpt-9/phasing/https://electricalvoice.com/dot-convention-in-transformer/Quick and dirty rule of thumb for power transfer:https://www.hwe.design/theories-concepts/transformer-dot-conventionHas other generally useful summaries:https://www.hwe.design/theories-concepts

author: MathWizard
author_rank: Super Contributor
timestamp: March 28, 2023, 11:16:45 pm
content: If you have some more basic parts, and a scope, or a simulator like LTSpice, there's some interesting circuits in this book below, A History of Impedance Measurments. I've made a couple of the pulsed DC circuits in the simulator, with a 0.1 ohm resistor as a deflection meter basically.