**Not really. Monster Cables are designed to possess attractive cosmetics, with no real regard for any tangible performance criteria. Blackgate caps, OTOH, DO have some measurably significant parameters. HOWEVER, none of those parameters is significant for power supply filtering. IOW: There are better caps available, at lower cost for filtering. Mind you: After purchasing some of those Dick Smith 'Joe Master' branded monstrosities once (and ONLY once) I can readily understand why some purchasers would spend the Bucks for a cap which is quite well made and performs respectably enough (Blackgate).
Why do you need to regulate the input voltage to the regulator? It is the function of the regulator to accept an unregulated input and provide a stable, regulated output.
The subject of the OP was "Isolated, regulated, toroidal step down transformer AC power supply design."
So I actually didn't indicate what 'it' was that was being replaced. Good on you for making that observation.
Brevity and relevance play a part in the formulation of my subjects for obvious reasons. Limited character space being one of them.
I did indicate what I wanted to replace 'it' with, in the subject matter of the OP.
So OK, why don't you help me select the 'self regulating' transformer that will eliminate all my over voltage problems. 240 VAC in (nominal), 9 VAC out. Fused at about 2 amps at the input. (it isn't critical.)
Tell me what else you need to know and I'll decide what I tell you, or not.
Regarding your speculation that "with modern regulators, pre-regulation is not likely to be required.":
"Not Likely" is a very soft qualification in the face of the observed behaviour of the applications performance during times of over supply. A
100% correlation suggests that it is VERY LIKELY. Statistically significant, in other words.
What isn't clear is why my Regs (assuming it is my Regs) misbehave. I have already conceded that the most cost effective action for me to take would be to replace the 7815/7915 pair with a new pair that DOES have the 30V spec. and see what happens.
But I may have to replace all other Regs in the applications power supply, for the same reason, before I get to the bottom of it. I don't have the necessary test equipment or the expertise to pre-determine which Regs are at fault.
Apparently AC regulation is a difficult task. TXU certainly do it VERY BADLY.
**Obtain a signal generator, capable of delivering a stable 50Hz sine wave. Operate it into a small (say) 50 Watt power amp. Drive the power amp into a suitable power transformer. That'll work.
**Bullshit. The only time pre-regulation will be required, is for under-Voltage events. That is easy enough to deal with.
**How (precisely) do they "misbehave"?
I have
**HUH? ALL 78XX/79XX regulators are specc'd virtually identically. Except for a couple of low power variants, all have a 35 Volt maximum Vin limit. Allhave a 2-2.5 Volt 'drop-out' Voltage. IOW: You should have AT LEAST 18 Volts DC at the regulator input terminal. There is a gotcha here too. You need to measure the ripple too, as any ripple which has peaks falling below the 2 - 2.5 Volt limit will impress that ripple on the output. IOW: Measure the ripple to the input of the regulators.
**Then you are screwed. You need to perform measurements to determine where the problem is. I'll betcha it ain't the regulators. Regulators are VERY reliable. And they all perform pretty much the same, if the have the same designation.
**And a stupid idea.
Ok, thanks for that. .It's probably bad advice, but thanks for trying.
Yep, Toroidal transformers are trendy ..because they are very popular!
That there are better transformer types (maybe 'Air Core', *groan*) I don't doubt for one moment, but I assume that there is good reason for the Toroidal transformer's popularity and it is likely to be cost/effectiveness.
(p.s. Weren't you the guy who WANTED to be excused from giving me 'advice'? I excused you. Did you change you mind?)
**There are APPROPRIATE transformers for each application. Air core transformers are not seen outside of RF work.
I don't
**Sure. Toroidals have a low radiated hum feild, are (nowadays) cheap to buy and they're reasonably efficient. However, their downsides make them the LEAST suitable choice for YOUR specific needs. An EI transformer would be better, whilst an 'R' core would be better again. It's horses for courses. You seem to be making a selection based on the simple criteria of: "Oh, it's what everyone else does." BIG mistake.
**I'm certainly toying with that idea. You appear to be spectacularly stupid. You have assiduously avoided parting with details of your application and have refused all attempts at offers of good advice.
**I don't care what YOU did.
Hey Trevor... He doesn't know anything about electronics. You're wasting your time discussing voltage regulators and anything else the slightest bit technical like oscilloscopes. He's probably had to search the net to find out what "CRO" means. I'll just watch and smile as this bizarre thread continues... :-)
On Wed, 28 Mar 2007 13:17:18 +1000, "Mark" put finger to keyboard and composed:
You are missing the point. There is no way that you can get 15VDC from a 9.00 VAC rms sine wave using only rectification, filtering and regulation, even under ideal circumstances. Hint: 15 is greater than 9 x sqrt(2) for all possible values of 2.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Yours is one of the very few contributions to this thread which was obviously written for my edification, and not for the purpose of an opportunistic 'free-kick', so to speak.
For that (rather solitary) attitude, I thank you.
P.S. Did you really take exception to this post because I top-posted it?
If not then the problem can't be 'top-posting', per se, right?
If so, then would you also explain what you find intrinsically offensive about a top-post as opposed to a bottom-post? Plenty of people bottom-post here but you don't complain.
Isn't it true that it is simply a matter of style, and therefore it is purely a subjective judgement that you make?
If it is true that you are genuinely aggrieved by my top posting style then, BECAUSE you have shown me the consideration due to any ordinary person, I can change it for YOU only.
Show me where I stated that. I stated that YOU were an idiot. Do you go to the doctor and say that you feel crook and leave it up to him to fix you???? Or, do you answer his questions regarding the symptoms.
No perils involved. Some jump on idiots straight away, while other take a little longer.
No, Chris. That wasn't the problem, although it may 'seem' that way to you.
I did not insult anyone who did not draw first blood. (I can think one possible exception, but I'll deal with the other 'Bob' later)
One of the reasons why it may 'seem' that way to you is because you may not be reading the posts in the chronological order they were written. The structure of the thread can give this illusion, but a more careful examination of the facts will reveal otherwise.
The policy I adhered to in this newsgroup is precisely the same one I adhere to in all other human relations. I treat people with exactly the same respect that they accord to me.
To quote myself from an a post I made in reply to 'Two Bob' earlier on this same thread:
"When people ask anything from me, they must display to me the same respect that I gave to them, when I asked something from them, or I will not submit to their demands.
If the cost of this personal policy is not receiving the help I requested then I would much prefer not to receive it. The price of self-respect is inestimable. Is that too difficult for you to understand?
The direct inference from your comments here and elsewhere on this thread is that you expect me (and possibly all newcomers) to submit to this bulling in order to receive the help that they need.
That is the definitive behaviour of a 'Phil-of-pile's."
end quote.
It's there; go read it for yourself.
Secondly, I may well have asserted "as facts a few things that happen not to be correct". We all harbour some false beliefs, even Phil. However, I usually qualify statements that I am unsure of with the pre-amble "the way I understand it". Not in all cases because like most people I understand some things better than others. There is not the slightest trace of arrogance in my manner. Indeed that may be the very reason why I have suffered SO MANY attacks. em.go.
People usually equate a certain level of arrogance in others with knowledge. If I display no arrogance then I am adjudged to have little knowledge (of electronics, in this case). A fact that I have repetitively and consciously confirmed, with simple admissions of that fact.
So the absence of arrogance AND the inability to defend myself with knowledge is like a beacon to those who like to play the humiliation game. It says: "soft target here, he can't defend himself, this is a chance to humiliate someone".
And so it started. Phil dives in and the 'Phil-o-philes' follow suit, safe in the knowledge that they can strike and not be stuck back.
Phil is nothing more than a common bully and so are the 'Phil-o-philes' that trail in his wake. The 'Phil-o-phile' is extraordinarily easy creature to identify. They are the perpetrators of the "me too" humiliations (flaming) once Phil as identified a target for them to attack. He is the 'decider', as he often describes himself (that he was describing himself is an inescapable conclusion , btw.). The one who "gets to decide what others should accept or believe."
Of course, the 'decider' must also have his first officers, and this too was implicit in his statement. He ascribed the power to "decide what others should accept or believe." with the qualities of a RIGHT, that is something held by some but not others.
He does not describe on what basis he shares this right with others, but it is a fairly safe assumption that it requires the display of superior knowledge or experience. Power is, of course, a perfectly negotiable commodity, so one can envisage any number of arrangements by which he might share this power out.
You see, the organisation of 'Phil-o-philes' is essentially and elitist club and membership has its privileges. The main privilege, is the pleasure drawn from the public humiliation of innocent targets (or even not so innocent targets, it doesn't really matter) These are his 'attack dogs' so to speak.
I don't discount the possibility that other members may have their own motivations for joining his club. Perhaps they actually like Phil but they are more likely to be scared of him. In some circumstances their decision to ally themselves with him is purely a practical one, it gets him off their back and frees up their time to pursue legitimate interests within the newsgroup. These people are more likely to be the casual observers of the humiliations rather than his agent provocateurs.
Now, the attitude that many of the casual observers of this all too predictable event have taken is that in order to receive the help I need, I must be prepared acquiesce to this bulling, and they have said as much (in once case EXACTLY that)
I am of the opinion that the price of self-respect is inestimable. If the cost of my refusal to acquiesce is that I don't receive the help that I need then I am prepared to pay that cost. I am completely untroubled by my position.
You ascribed to me the quality of idiocy. You are, after all, a 'decider'.
I retorted with a jest. After all, I do FEEL like and idiot for asking for help at 'aus.electronics'.
I feel like an idiot, not because I put the question in the wrong forum OR because the expertise isn't available here to solve it, but BECAUSE I should have known better what you and your fellow 'Phil-o-philes' would EXPECT me to 'put up with' in order to get it. Quod Erat Demonstrandum.
I think that the reason why people were disagreeing with you and agreeing with Phil has nothing at all to do with anyone liking Phil. If I agree with Phil and not with your understanding of the operation of regulators, rectifiers and the properties of sine waves, I can assure you that it is for purely technical reasons. I did put some technical comments interspersed within the text of your previous message (quoted above) and you might find these comments useful, both as technical pointers and as reasons why people might have gained the impression that you were asking the wrong question in your original post.
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