transformer phase shift - how to measure with oscilloscope 3

[MRSSPOCK]

I know this might seem like a schoolboy level question, but I'm afraid I'm stuck.

If I have an unknown transformer and what to determine if there is a phase shift, how can I do it with my two channel scope, considering both channels use the common ground, and so by connecting two channels I am really creating a direct physical connection between the two otherwise isolated primary and secondary coils.

Thanks

I think I am going to be embarassed by the simple answer.

 

[Skogsgurra]

Yes, I knew them both. I corresponded with Bob and appeared in a few of his "What's this xxx stuff, anyhow". He even sent me a card when I was at hospital for a by-pass surgery. He had so much time for everyone.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[VEBill]

Many DC-DC converters are not isolating and use only an inductor (single winding), not a transformer. Design still involves dealing with the magnetic properties of the core and coil.

A really nifty control IC is the LTC3780. YouTube has some great explanations of how it can smoothly transition between buck and boost. It's certainly interesting. eBay sellers offer preassembled modules for ~US$10+ price class.

 

[waross]

https://en.wikipedia.org/wiki/Jim_Williams_(analog_designer)[/URL]]Jim Williams (analog designer)
From Wikipedia, the free encyclopedia

Jim Williams
Born April 14, 1948
Died June 12, 2011 (aged 63)
California
Nationality American
Occupation Electronics engineer

James M. Williams (April 14, 1948 – June 12, 2011) was an analog circuit designer and technical author who worked for the Massachusetts Institute of Technology (1968–1979), Philbrick, National Semiconductor (1979–1982) and Linear Technology Corporation (LTC) (1982–2011).[1] He wrote over 350 publications[2] relating to analog circuit design, including 5 books, 21 application notes for National Semiconductor, 62 application notes for Linear Technology, and over 125 articles for EDN Magazine.

Williams suffered a stroke on June 10 and died on June 12, 2011.

https://en.wikipedia.org/wiki/Bob_Pease[/URL]]Bob Pease
From Wikipedia, the free encyclopedia
Jump to navigation
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Robert A. Pease
Full face portrait, showing mature glasses-wearing adult male with white hair and a full white mustache and long beard
Born August 22, 1940
Rockville, Connecticut
Died June 18, 2011 (aged 70)
Saratoga, California
Nationality American
Other names Bob Pease
Alma mater Massachusetts Institute of Technology
Occupation Electronics engineer
Known for Analog integrated circuit design, technical author

Robert Allen Pease (August 22, 1940 – June 18, 2011) was an analog integrated circuit design expert and technical author.[1][2] He designed several very successful "best-seller" integrated circuits, many of them in continuous production for multiple decades. These include the LM331 voltage-to-frequency converter,[3] and the LM337 adjustable negative voltage regulator (complement to the LM317).
Contents

1 Life and career
2 Death
3 Publications (partial)
4 See also
5 References
6 External links

Life and career
Pease was born on August 22, 1940 in Rockville, Connecticut.[4][5] He attended Northfield Mount Hermon School in Massachusetts, and subsequently obtained a Bachelor of Science in Electrical Engineering (BSEE) degree from Massachusetts Institute of Technology in 1961.
...............
My favorite programming language is ... solder
...............
Death
Flag at half-staff at National Semiconductor on June 21, 2011

Pease was killed in the crash of his 1969 Volkswagen Beetle, on June 18, 2011.[25][26][27] He was leaving a gathering in memory of Jim Williams, who was another well-known analog circuit designer, a technical author, and a renowned staff engineer working at Linear Technology. Pease was 70 years old, and was survived by his wife, two sons, and three grandchildren.[27] The sudden death of Pease triggered a small flood of remembrances and tributes from fellow technical writers, practicing engineers, and electronics hardware hacking enthusiasts

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

"Good luck. And remember that the North Pole actually is a South Pole. By definition. "Sometimes called the "North seaking pole."
Brings back memories of the years when we were taught to use our left hands for the right-hand-rule. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MRSSPOCK]

I think a miracle might be in order, never mind "good luck" !

What surprises me is that with transformers so widespread, (there are probably 50 in the room I'm now sitting in, within various appliances), that the design of such seems to have even many professionals view the transformer design with "Trepidation". Surely the world must be full of transformer designers who know precisely what they are doing, and the mystery is, how has this knowledge not now become common and widespread? Is it because it really is complicated, or they like to keep it a secret

 

[IRstuff]

"Surely the world must be full of transformer designers"

Why do you think that? Few consumer systems that require transformers are seriously constrained by size, weight, and power. And why would a walwart designer design their own transformer when they can order one that close to their needs, off-the-shelf? No designer in their right mind would contemplate designing and manufacturing their own transformers, for the same reasons they wouldn't contemplate designing and manufacturing their own capacitors, resistors, inductors, or transistors.

And, for the most part, transformers are not an avenue for new design explorations, just like no one contemplates designing new resistors or capacitors. We've been using the mostly same dielectrics for probably 40 years. Supercaps are probably the biggest deviation from that, and they're a pretty niche product.

In a similar vein, could you, would you, design and fabricate the 1/4-20 screw in your picture from scratch for your next project?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[zappedagain]

Wow, 7 years already since we lost those two. Seems like yesterday...

Z

 

[MRSSPOCK]

@IRstuff

I just assumed that transformers had to be tailored more precisely to certain applications, but from what you state, they are generally chosen as the best available for the purpose required. Having said that, Farnell. RS etc, do sell hundreds of options of coil formers. ferrites etc, in quantities less than 10. I wonder who their target market is.

As regards threads, I regularly need to cut some bastard thread to match up with some already existing component, generally someone has cut a metric thread onto some vintage machine component. 1.75" x 1.5mm pitch, just last week for example.

 

[waross]

I have cut a few threads. I use off the shelf dies and taps.
I had one application where a machine shop made an adapter to fit a replacement part with a right hand thread onto a part with a left hand thread.
Never any design involved, just followed existing practice.
Back to transformers.
Some basics:
Core permeability flux density and saturation.
Amp turns.
Taken together, more Amp turns means higher flux density until the limit is reached at saturation.
Use this information to calculate the inductive reactance of the transformer, viewed as an inductor at a specific frequency.
Now use this to calculate the voltage required to push the core to saturation.
With voltage and frequency, calculate the Volts per Hertz ratio.
The Volts per Hertz ratio will tell you the safe operating voltage over the linear range of the core.
There is more but that will give you a start.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MRSSPOCK]

Thanks for all your advice, comments, links, pdf's etc. All good stuff. Time to get my head down now and generate some smoke!!!

 

[VEBill]

It's not uncommon to wind one's own custom transformers for RF projects. These days they'd typically be of the toroid ferrite-core variety, or in previous generations (e.g. 1950s) they might have been air core. Commercial products (radios) would more-typically use Off-The-Shelf transformer 'cans'. For an existing design, just follow the build instructions to wind the coils. For something of your own design, the core company (e.g. Amidon Associates) provides data sheets and plenty of 'White Paper' guidance.

Modern DC-DC converters are somewhat similar. If you're building a one-off example, then you might choose to find a suitable core and wind your own coil. Or just purchase a pre-wound inductor (or extract one from a junked PC power supply). As mentioned already, many DC-DC converters are non-isolating and use only a (single winding) inductor (not a transformer).

 

[zappedagain]

I'll second the plug for Amidon. Their Tech Data Flyer is still useful after 17+ years!

Z

 

[MRSSPOCK]

Sorry for asking this question here, but I can't find any forum administration type contact, so my question is, is there a means to send a Private Message on this forum? I can't find any way to do it. Thanks

 

[IRstuff]

No, there is not such a thing. The intent is to share information and knowledge.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[waross]

Mrsspock:
Are you concerned with a 50/60 Hz transformer or an RF transformer?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MRSSPOCK]

No, I simply wanted to run something past an individual. Not for technical advice, more for administrative forum advice. Not to worry.

 

[MRSSPOCK]

So, I've had a slight change of direction on this matter. Instead of using my old strobe light, I bought one of these from ebay. (I presumed the output would be AC but it isn't).

I have an idea, which might help anyone else who would like to learn more about this subject.

I have already pulled this device apart and taken a photograph of both sides.

I inverted the reverse side so as to give me a view as if I am looking straight through the board.

I then placed both images beside one another, so as to provide a TOP view and BOTTOM view, to make reverse engineering it a bit easier.

Using DIPTRACE I then superimposed the relevant components roughly in their locations, then wired it all up.

(Maybe this is a clearer image for the components names - I can't seem to make it use up the page width)

So, suppose some one of you who has a reasonable understanding of this circuit, is willing to help me along as I recreate this circuit on a breadboard, and provide a means whereby I can tweak certain components / parameters, and observe the output.

It might serve as a good reference for someone else likely to make all the cock ups I am about to make.

I purposely said that if some ONE of you, because quite honestly, I think the whole exercise would just turn into mayhem, if I was getting advice from 10 different inputs, possibly many pointing me in many different directions.

(Is it maybe even better that this would be done off line, then the final result uploaded at the end?)

The device is on ebay is only £4 so it is dead easy for someone else to easily join in and hack up one for themself, if they too are keen to use the "learn by burn" process.

The first thing I want to do, is to ditch all the parts that relate to the USB output, but to be honest, my first hurdle is understanding how this circuit works. I can understand a basic oscillator but how this Zener is positioned is confusing me. I'm pretty confident that all my components on my schematic are listed correctly, except for two items.

1. I am presuming that is a 7.5 Zener diode.

2. The transformer dots are just as was the default from the component library in Diptrace.

If anyone can spot any immediate cock ups in how I have captured the schematic can you please point it out. (Thanks).

So if anyone has any comments, and anyone feels like volunteering to be my mentor, please feel free to take the plunge!

It might all turn into a big mess pretty quickly, but I'm ready to do the donkey work, if it seems a useful exercise to any of you.

 

[IRstuff]

Your schematic does not look right. The shared node between C4 and C1 appears to be tied to the USB shield

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[Skogsgurra]

Better than a cross-Word puzzle! This drawing may be easier on the Eyes:

I would run that on LT Spice if I had the time to do it. Anyone?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MRSSPOCK]

@ IRStuff

Yes thanks, you are correct.

The USB shield and USB ground are tied to that node.

I did a test, and with no load on the USB port, the output voltage is 6.5V, whether connected to the USB ground or the boards groundplane.

I then put my probes between USB ground and the board grounplane and read 0.0V

I will try to create a better image. That is hard to read.

Thanks