John Curl's Blowtorch preamplifier part II

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marce

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Joined 2007
Triodethom said:
Enumeration of good practices for emc control of digital cable in this application would be enlightening for many of us. :)
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Despite you dig, (Henry Ott buy the book) is a good start.
Todays digital is a problem due to the ever increasing rise time of the signals, putting more and more high frequency harmonics into the mix. SO even with relatively slow overall clock frequencies you have to employ high speed design considerations due to the signal rise time....
Where possible and where costs allow, flex cables allow the best option for signal control, if not double sided FFC, then single sided with GND/sig and the best option try to keep everything on the board, as soon as you add any cable be it internal or external to the box you are adding an antenna and possible EMC problems.
It is the signal rise time that determines whether a design is high speed.
 
Triodethom

Triodethom

Member
Joined 2009
marce said:
Despite you dig, (Henry Ott buy the book) is a good start.
Todays digital is a problem due to the ever increasing rise time of the signals, putting more and more high frequency harmonics into the mix. SO even with relatively slow overall clock frequencies you have to employ high speed design considerations due to the signal rise time....
Where possible and where costs allow, flex cables allow the best option for signal control, if not double sided FFC, then single sided with GND/sig and the best option try to keep everything on the board, as soon as you add any cable be it internal or external to the box you are adding an antenna and possible EMC problems.
It is the signal rise time that determines whether a design is high speed.
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It was intended as a request for info more than a dig. Sorry that it came off that way . Too often this blog make what my philosophy prof would call a faulty leap by leaving out steps and references in the logical progression . The assumption of total knowledge of all small and some large facets of this hobby ( and field of work for some) is common in normal banter and i can not hold anyone to fault for it . Thanks for the help and reference. :rolleyes:
 
jneutron

jneutron

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Joined 2004
Kastor L said:
The only sensible thing is every government making ultra massive solar panel fields and deep sea windmills powered by ocean currents.
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Yup..

Then all we have to worry about is disposing of the silicon fabrication processing waste for all those cells, as well as air heating of all those solar panel fields dissipation of 85% of the solar influx rather than having some of the solar reflected back into space. Talk about global warming..:eek:

I'm still trying to figure out how a windmill uses ocean currents.:confused::confused:

Don't forget all that 3 phase undersea cabling using oil as a dielectric, and the worldwide shortage of neodymium. As well as the modification of the gulf stream currents so that the seacoast of maine has water temps in the 80's F. (they could use that of course..that water's cold..) Not to mention the extra gas the lobstermen will need to get out to the cold water...:(
Kastor L said:
After that, prohibit caffeine, alcohol to 30+ age limit and make all sports free
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Which of course, either kills all the fun therefore limits procreation to solve the population problem, or gives everybody something to watch in lieu of...

I see right through your despicable works, Dr Evil...you can't fool me..you just want global domination.

jn
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
Hi,

I'm still trying to figure out how a windmill uses ocean currents.
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A windmill + a current driven turbine perhaps?

Why not deplete this planet completely, use geothermics and leave after that?

I can accept windmills provided they're made invisible to terrestrians .

Photovoltaic panels are so like TV antennae on roofs. Yuk.

How did this thread turn into an eco discussion anyway?

Ciao, ;)
 
jneutron

jneutron

Member
Joined 2004
fdegrove said:
Hi,
A windmill + a current driven turbine perhaps?
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Perhaps, but wind and sea are two different things. I'm not sure that a windmill blade will work underwater. Can anybody tell me if the bernoulli effect is applicable to an incompressible media such as water?

fdegrove said:
I can accept windmills provided they're made invisible to terrestrians .
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Well, don't look.. see, problem solved..;)
fdegrove said:
How did this thread turn into an eco discussion anyway?
Ciao, ;)
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You mean, as opposed to the extremely focussed discussion this thread has always been?

jn
 
scott wurcer

scott wurcer

R.I.P
Joined 2004
jneutron said:
Perhaps, but wind and sea are two different things. I'm not sure that a windmill blade will work underwater. Can anybody tell me if the bernoulli effect is applicable to an incompressible media such as water?
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Tidal Energy | Islay Energy Trust

Looks the same to me. "There are no incompressible fluids" , such fond memories of the sound propagation in water thread.
 
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jcx

Member
Joined 2003
*3**Airfoils and Airflow really worth looking
3.16 Consistent (Not Cumulative) Laws of Physics


We have seen that several physical principles are involved in producing lift. Each of the following statements is correct as far as it goes:
• The wing produces lift “because” it is flying at an angle of attack.
•The wing produces lift “because” of circulation.
•The wing produces lift “because” of Bernoulli’s principle.
•The wing produces lift “because” of Newton’s law of action and reaction.

We now examine the relationship between these physical principles. Do we get a little bit of lift because of Bernoulli, and a little bit more because of Newton? No, the laws of physics are not cumulative in this way.

There is only one lift-producing process. Each of the explanations itemized above concentrates on a different aspect of this one process. The wing produces circulation in proportion to its angle of attack (and its airspeed). This circulation means the air above the wing is moving faster. This in turn produces low pressure in accordance with Bernoulli’s principle. The low pressure pulls up on the wing and pulls down on the air in accordance with all of Newton’s laws.

See section 19.2 for additional discussion of how Newton’s laws apply to the airplane and to the air.

3.17 Summary: How a Wing Produces Lift


• The flow pattern created by a wing is the sum of the obstacle effect (which is significant only very near the wing, and is the same whether or not the wing is producing lift) plus the circulation effect (which extends for huge distances above and below the wing, and is proportional to the amount of lift, other things being equal).
•A wing is very effective at changing the speed of the air. The air above is speeded up relative to the corresponding air below. Each air parcel gets a temporary change in speed and a permanent offset in position.
•Bernoulli’s principle asserts that a given parcel of air has high velocity when it has low pressure, and vice versa. This is an excellent approximation under a wide range of conditions. This can be seen as a consequence of Newton’s laws.
•Below-atmospheric pressure above the wing is much more pronounced than above-atmospheric pressure below the wing.
•There is significant upwash ahead of the wing and even more downwash behind the wing.
•The front stagnation line is well below and behind the leading edge.
•The rear stagnation line is at or very near the trailing edge. The Kutta condition says the air wants to flow cleanly off the sharp trailing edge. This determines the amount of circulation.
•An airfoil does not have to be curved on top and/or flat on the bottom in order to work. A rounded leading edge is a good idea, but even a barn door will fly.
•Air passing above and below the wing does not do so in equal time. When lift is being produced, every air parcel passing above the wing arrives substantially early (compared to corresponding parcel below the wing) even though it has a longer path.
•Most of the air above the wing arrives early in absolute terms (compared to undisturbed air), but this is not important, and the exceptions are doubly unimportant.
•Lift is equal to circulation, times airspeed, times density, times wingspan.
•Well below the stalling angle of attack, the coefficient of lift is proportional to the angle of attack; the circulation is proportional to the coefficient of lift times the airspeed.
•Air is a fluid, not a bunch of bullets. The fluid has pressure and velocity everywhere, not just where it meets the surface of the wing.
•There is downward momentum in any air column behind the wing. There is zero momentum in any air column ahead of the wing, outboard of the trailing vortices, or aft of the starting vortex.
•Vortex lines cannot have loose ends; therefore you cannot produce lift without producing wake vortices.
•Induced drag arises when you have low speed and/or short span, because you are visiting a small amount of air and yanking it down violently, producing strong wake vortices. In contrast there is very little induced drag when you have high speed and/or long span, because you are visiting a large amount of air, pulling it down gently, producing weak wake vortices.
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