Not so fast Ed
What is the reason you used two transformers in series/parallel config to get to the pos and neg peak line voltage? Seems to me you introduced an unnecessary inaccuracy by using two transformers that may not be well matched as to exact turns ratios.
We're dealing with presumably small DC voltages. I believe a better solution would be (more accurate) to use a single transformer and a matched pair of diodes?
jan didden
Jan,
My symbol library only shows the modern 4 coil design as two transformers, it really is just one. Random diodes were within a few milivolts. However I still am off by about 35 millivolts due to capacitor differences and possibly winding issues. I did have to tweak the capacitors to get to where I am. In the final version I will use a 250 ohm trim pot.
As to the voltages turns out they are not so small. The AC line is varying by about 2 volts and the DC offset from just the 40 watt bulb at the end of an extension cord and test box is a few volts!
Thanks for the comments!
Interesting version. Capacitor tolerance does not seem to be as tight as transformer winding accuracy and lacks the isolation (as you mentioned). I chose an EI transformer for this as they tend to have wider bandwidth than say an O core.
Since it does show me the offset it will work when if then next stage is added which is a device to reduce the offset.
His cure is to place a capacitor in series with the line. The capacitor is protected by diodes to make sure you do not exceed the voltage rating. Turns out it doesn't really work!
Ed how does the C tolerance figures in this? I would think that if you take a long enough integration time it would be moot. Or is it the delta in leakage?
jan
Here, the first three years of earning an engineering degree are mostly spent learning physics and math. Several semesters of integral calculus, differential equations, linear algebra (for me anyway, back in the day), probability and statistics, statics and dynamics, thermodynamics and so on. No, not a lot of quarks and bosons but you really have to know physics and be really good at math to earn an engineering degree here.
John
Jan
I normally just pick two out of the bin, when the mismatch in my circuit showed up I noticed one was Nichicon and the other Panasonic. A quick try of several same brand still showed a bit of difference. Ended up with 2 Panasonics. My bet would be leakage and transformer differences, but that would be an OPINION based on my experience and perception, since the proof of concept worked it does not seem to be a problem at this time.
In the alternate circuit I suspect there is also a hidden voltage divider including the unshown source resistance so actual value tolerance may also have a small effect.
Of course this could be a mistake on my part as it is when the details don't quite match is where you can learn things. But since I never make mysteaks no worries here.
ES
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Maybe that is why the US now leads in technology. In the UK, one of the heads of an engineering institution complained that UK degrees contain too much "pure maths" (they actually contain none, and inadequate amounts of applied maths). I have had trouble getting electronics research papers published in the UK because the journal referees said they contained too many equations - I had to point out that I was only using school-level maths.jlsem said:
When quantum computing really takes off, engineers may need to learn about bosons and fermions too!
When I was in college my buddy now known as JJ mentioned his local college had calculus as a senior level subject for electrical engineers. I found this hard to believe as that is really the starting point for electrical engineering. My college had an electrical engineering intro first year course, but only one semester, basically DC circuit analysis, Thevenin and Norton and only grazed capacitors and time constants.
So when I ran into two fellows applying for graduate school from that local college I asked them if calculus was really a senior level course. They told me not really... most folks took it second semester junior year to get the hard stuff out of the way so they could coast senior year.
One of my circle teaches at the local semi-prestigious University and has mentioned every so often the senior faculty change what is being taught based on what their area of research indicates will be needed. However they do make sure no one escapes anymore without mastering the basics.
Once again, we have people evaluating areas where they have little or no expertise. This is no surprise, as many here are from different countries, with different educational systems.
When I spoke of physics vs engineering, I meant advanced physics, masters to PhD level in atomic structure.
In the USA, everyone who takes either engineering or physics has to get math to beyond differential equations, at least. This, of course, includes calculus and vector analysis. Without it, you can't understand what the 'symbols' mean in a serious textbook of engineering. (Sorry Bob Cordell, you know what I mean) It would appear, in general, where they diverge. Engineering, then concentrating on primitive device theory and circuit design and analysis.
Physics, at least in my experience, went more forward in math, concentrated on properties of light, heat, etc, and advanced equation development of mechanics that Newton and Kelvin would have been comfortable with. At the undergraduate level, quantum physics was given limited exposure (or at least it was when I went to school) and could be essentially ignored, at this level. Of course, people who wanted to go on and become an atomic physicist had to concentrate on this area, and then spend several years at graduate level, learning it well.
Engineers generally get just enough physics to read the equations, and understand the primitive models of 'electricity flow', Maxwell's equations, etc. etc. That is one major factor causes endless argument on this website. Engineers can often think that they know 'everything'. Everything else is 'impossible'. And so it goes.
When I spoke of physics vs engineering, I meant advanced physics, masters to PhD level in atomic structure.
In the USA, everyone who takes either engineering or physics has to get math to beyond differential equations, at least. This, of course, includes calculus and vector analysis. Without it, you can't understand what the 'symbols' mean in a serious textbook of engineering. (Sorry Bob Cordell, you know what I mean) It would appear, in general, where they diverge. Engineering, then concentrating on primitive device theory and circuit design and analysis.
Physics, at least in my experience, went more forward in math, concentrated on properties of light, heat, etc, and advanced equation development of mechanics that Newton and Kelvin would have been comfortable with. At the undergraduate level, quantum physics was given limited exposure (or at least it was when I went to school) and could be essentially ignored, at this level. Of course, people who wanted to go on and become an atomic physicist had to concentrate on this area, and then spend several years at graduate level, learning it well.
Engineers generally get just enough physics to read the equations, and understand the primitive models of 'electricity flow', Maxwell's equations, etc. etc. That is one major factor causes endless argument on this website. Engineers can often think that they know 'everything'. Everything else is 'impossible'. And so it goes.
Hi jlsem,
You are exactly right. It all works both ways and there is a broad distribution of talent, creativity and common sense across the members of all disciplines. I know some people with a physics background who hardly know which end of a soldering iron to hold. I also believe that most EE's who went to a decent college and paid attention know enough about physics and math to be outstanding engineers of audio equipment. Neither an EE degree nor a physics degree is a guarantee that the person will have creativity, common sense and an open mind.
Then there are some people who assert that some others who don't understand/accept high-end snake-oil because they did not have an adequate background in physics. Such generalizations are a bunch of cr@p. Mind you, I am not saying all of the high-end stuff is snake oil, but a good deal of it is (i'd say at least 50% is marketing driven bull). Let's all keep an open mind, but let's all be a bit cautious about fooling ourselves as well. One of the challenges we all face is to separate out the snake-oil from the stuff where someone is onto something, and doing it with an open mind. Profiling people based on college degree is not helpful.
Cheers,
Bob
JC, this is highly underestimated, regarding university engineering studies, IMO. You probably have never graduated in engineering.
During electrical engineering studies, we had studied more or less the same maths as our colleagues at math+phys studies. During first three years of study, mathematics and physics took at least 60% (more in fact) of the lectures.
As usually, you oversimplify and play a kind of game of yours.
During electrical engineering studies, we had studied more or less the same maths as our colleagues at math+phys studies. During first three years of study, mathematics and physics took at least 60% (more in fact) of the lectures.
As usually, you oversimplify and play a kind of game of yours.
1/f Noise Is What I Mean....
Is the maths adequate ???f
Generally yes, but to describe the really fine points of audio is a resounding no in my experience.
Of course every last minute can be mathmatically described, but this takes extraordinary computer analysis in addition to the hitherto standard methods.
Standard measurements and the ear are perfectly valid criterion....if one can't fine polish a turd, at least shape it to an aurally acceptable form...
Eric.
Is the maths adequate ???f
Generally yes, but to describe the really fine points of audio is a resounding no in my experience.
Of course every last minute can be mathmatically described, but this takes extraordinary computer analysis in addition to the hitherto standard methods.
Standard measurements and the ear are perfectly valid criterion....if one can't fine polish a turd, at least shape it to an aurally acceptable form...
Eric.
A well engineered piece of audio equipment is mere a starting point for good audio reproduction.
There are numerous other factors in play beyond the focus of the EE:
- perception of sound (how much distortion do we tolerate before it becomes audible? masking effects);
- room acoustics;
- psychological factors (it is expensive so it should be good...);
- optical factors (it looks great so it also should sound great...).
In that perspective IMHO over 90% of this thread does not make too much sense.
There are numerous other factors in play beyond the focus of the EE:
- perception of sound (how much distortion do we tolerate before it becomes audible? masking effects);
- room acoustics;
- psychological factors (it is expensive so it should be good...);
- optical factors (it looks great so it also should sound great...).
In that perspective IMHO over 90% of this thread does not make too much sense.
The Public Ain't Totally Stupid.....
IME the 'noddie types' will tell you much more valuable subjective critique information than the supposedly educated (and perhaps misinormed/indoctrinated) audiophile types.
Eric.
Yup, agreed, too much claimed audio improvement stuff is indeed 'snake oil', ......but some is not, and it is these observations and assertions that are worth taking note of and expanding.
IME the 'noddie types' will tell you much more valuable subjective critique information than the supposedly educated (and perhaps misinormed/indoctrinated) audiophile types.
Eric.
Interesting. I once made a mistake too; I thought I was wrong but I wasn't
jan didden
Well, everyone, I tried. For the record, my academic background was the first 2 years engineering, second 2 years, physics, final year, BA physics, with minor in electronics engineering. So, I have studied both programs. Then 4-6 years as a jr. engineer, etc, I went back to UCB and took undergraduate and graduate classes in ANALOG electronic engineering, only with RG Meyer and DO Pederson. This brought me 'up to speed', so to speak, to understand modern electronics design, that I needed to move forward. Therefore, MY background is somewhat scattered and sometimes problematic. However, it works for me, and my success in audio design should be noted, if you have any doubts.
My comments here are mostly hoping to give better understanding of 'misunderstandings' between many contributors here. When Ed Simon made his first response on the topic, I berated him for causing even MORE dissent here, with his strong personal opinions on who IS and who IS NOT a qualified engineer. I was arguing the other way, trying to unite everybody. Oh well.
My comments here are mostly hoping to give better understanding of 'misunderstandings' between many contributors here. When Ed Simon made his first response on the topic, I berated him for causing even MORE dissent here, with his strong personal opinions on who IS and who IS NOT a qualified engineer. I was arguing the other way, trying to unite everybody. Oh well.
Listen To The Old Blokes......
Hi John, I think that at least some of us here respect your experience and assertions, and learn by what you say related from real world experiences....I know that I do so.
My view regarding audio reproduction is that 'the proof is in the eating'...good audio replay is good audio replay and mathematical models help to arrive at a solution but they are not sufficient models for audio to the high degree.
An engineering mind constructively combined with perceptive ears is the key....I sure that I am not telling you anything new....
Regards, Eric.
Hi John, I think that at least some of us here respect your experience and assertions, and learn by what you say related from real world experiences....I know that I do so.
My view regarding audio reproduction is that 'the proof is in the eating'...good audio replay is good audio replay and mathematical models help to arrive at a solution but they are not sufficient models for audio to the high degree.
An engineering mind constructively combined with perceptive ears is the key....I sure that I am not telling you anything new....
Regards, Eric.
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