Isolated, regulated, toroidal step down transformer AC power supply design.

You're not wrong. I can imagine him asking on an automotive newsgroup for advice about a misfiring engine.

"What kind of engine is it?"

"An internal combustion one."

"No, I mean is it petrol or diesel? Four-stroke or two-stroke."

"You don't need to know that, so I'm not going to tell you. My engine is misfiring and I want to know how to stop it from doing that."

"You need to tell us some specifics so we can give you relevant advice."

"Hey, *I* decide what I tell people - that's *MY* right. You don't need to know any more than that it's an internal combustion engine and it misfires!! I personally think that if I can get 150 octane fuel, that'll solve my problem. Why is it that you instantly jump on me for exercising *MY* right to only tell you what you need to know?"

"OK. Then what kind of fuel does it use now?"

"It uses liquid hydrocarbons. You don't need to know more than that. Oh and by the way Mr Smarty Mechanic, you didn't know that to remove a spark plug, you have to turn it ANTI-CLOCKWISE!! I knew that, but you didn't!! Now who's the knowledgeable one in this discussion? Nar nar nar!!!"

Etc...

Reply to
Bob Parker
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Hah hah hah..........very good Bob. You don't write scripts for a living do you? If not, then consider a new profession as a stand-up comic. Based on the above, you'd do very well :-).

ruff

Reply to
roughplanet

Thanks! Just trying to make a bit of an analogy there. :-)

Bob

Reply to
Bob Parker

If you haven't tried already, try plugging your device into a sinewave inverter or an UPS (dual conversion type) to see if your theory of "regulated AC" solves your problem.

Reply to
chinsta00

On Thu, 29 Mar 2007 17:56:23 +1000, "Mark" put finger to keyboard and composed:

Is this what you mean?

D1 o-----|--|>|-----|-----o +V | _|_ +

9VAC | --- C1 rms | | o----- )---------+-----o 0V | _|_ + | --- C2 | D2 | |--|Ask Phil about it, he knows.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

so just where does one place the magnetic shunt in a toroidal core for a CVT?

besides, most of the people who used to design these have died.

Reply to
Terry Given

yeah, I second that. I wont buy a cap if I cant get a datasheet for it. one 10uF cap with 27 Ohms ESR was enough for me. Of course now, thanks to Bob, I can measure that in a jiffy :)

Cheers Terry

Reply to
Terry Given

wow. you really are making life difficult for yourself. Of course it doesnt take much to attract flames, but I would recommend a strategy other than begging for them.

For the record, as Trevor has repeatedly pointed out, regulating AC is actually pretty hard. and 1% is an astonishingly tight spec - assuming closed-loop control, you will need a reference that is quite a bit better than 1% (all the other tolerances stack up), *all* the relevant components in the feedback sensing loop will need to be < 1% etc. It is most assuredly *NOT* a "simple thing".

If you really insist on it, then why not make a variable inductor, using an E-core. Place this in series with the 9Vac output, and devise a controller which increases the inductance as the line voltage increases, and vice-versa. A suitable variable inductor is pretty easy - a pair of windings on each outer leg, in series and phased such that the centre-leg flux cancels. Then place a winding around the centre-leg, and run DC through it. Enough DC will make the core saturate, and the total AC inductance will drop to the air-cored value; no DC and the inductance will be maximised.

but if you cant measure ripple current, I doubt you can make one of these (although it is straightforward to make such a system which will meet your requirements)

I say this as an experienced power supply design engineer, not some amateur. If a customer came to me with this request, I would spend some time trying to ascertain (by asking questions and getting more information) what the real problem is, then work towards solving that. And if the customer insisted I do what they asked, I would wave goodbye and then have a good laugh, swapping the story with mates over a beer, whilst maligning clue-free customers.

Cheers Terry

Reply to
Terry Given

I second that, well done Bob!

Its nice to see someone get a roasting (and a polite one at that) who actually deserves it.

Cheers Terry

Reply to
Terry Given

We had the same issue when I was working for a major whitegoods manufacturer in the late 80's. The 7805's were getting pop-rivetted to the board through the heatsink, then we'd be getting failures. Can't remember the failure rate though. The 7805 tab transferred the shock of the pop-rivetting action to the the 7805 die and fractured it. Same solution, no further problem.

Reply to
dmm

Thanks Terry. Now I'm thinking about how to make a meter which shows musicality in capacitors. Maybe do a frequency sweep to see how it performs at the bass vs midrange vs treble ends of the spectrum? ;-)

Bob

Reply to
Bob Parker

the

though.

die

yep. good old AN1040 strikes again. I had to explain to the C.M. that its basically a lump of glass soldered to a copper tab, and smacking it hard with a hammer was a bad idea.

I had an even funnier one with the same UPS - doing a forensic analysis on a failed unit, the flyback battery charger had died. I desoldered the FET & heatsink, and when I lifted it out of the PCB, the FET spun freely. The CM had used a nylok nut, and the nylon had melted, dribbling out the back of the nut, which then worked itself loose. oops. So I spec'd the same captive-spring-washer nuts we used, which were really cute - they had a spring washer that looked like a belleville with 4 radial cuts, and the center of the nut was crimped around this, so the spring washer could spin. lovely, and cheap.

Cheers Terry

Reply to
Terry Given

perhaps you could have a web-enabled instrument. If it can find a datsheet, it gives it a low score, and vice-versa.

Hey, who makes your kits in USA? I want to recommend it to one of my customers there.

Cheers Terry

Reply to
Terry Given

Yeah, sounds good to me! Now that DSE's stopped making kits, about the only place anyone can get an ESR meter one is from John's Jukes in Vancouver, Canada. Website:

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HTH

Bob

Reply to
Bob Parker

**YIKES! 27 Ohms! I purchased a Joe Master (long before I built Bob's magnificent device) and whacked in a power supply I was servicing (it was urgent and DSE was just up the road). The cap went belly-up within a week. The ripple rating must have been appalling, as it was operating well within Voltage limits. A decent cap from Farnell did the trip.
--
Trevor Wilson
www.rageaudio.com.au
Reply to
Trevor Wilson

thats what I said (or at least paraphrased). It was across a TL431 used as a voltage reference, to stop it oscillating. except it oscillated, so I looked hard, and was very, very surprised. I had a whole bunch, and they were all about that bad. quite what you could use it for I dont know.

I purchased a Joe Master (long before I built Bob's

I'd believe that.

Cheers Terry

Reply to
Terry Given

The only smart thing you have done is post to this forum with your problem. Where you have proven you are an idiot is by your attitude. You can come along here for a number of reasons. For information, for enlightenment, for the friendly banter, or as in your case, to be ripped to shreds because of your arrogance.

You have admitted a number of times your lack of electronic knowledge. Then you argue black is white when anyone tries to point you to the right path. If you know the answer to your question, then piss off. If you dont, then listen to those who are willing to help you.

Reply to
Two Bob

Aha! Your're Mark! I knew he had to be a troll someone had made up to torture us!

Reply to
Poxy

the

though.

7805 die

In my last job we used those sort of nuts (with integrated washer) in conjunction with self broaching threads that were pressed into pcbs. The nut and thread held down a plastic housing, and that wasn't going anywhere. It's a nice idea.

Reply to
dmm

Ok, good idea.

The computer is in the dinning room, we rarely 'dine' together.

The Hi-Fi is in the bedroom. (where else!). It is part of my personal Hi-Fi, not my sons.

Reply to
Mark

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