Sometimes the fuse rating is such that it sags a little bit every time it charges the filter caps, and eventually it gives way.
Sadly, though, I think I would not bet against you on this one.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Grin.. Hi Phil, Well my semi-silly model of 1/2 the earth in sunlight and all of it radiating is ... silly. But I just use it to remember the ~500W/m^2 number.
George H.
It fixed it -- so far so good. One of those lucky breaks. (I hear ya -- when a fuse goes, there's usually a good reason for it).
All other components on board tested good before I jumped the fuse with 28 gauge.
A 2 grand Philips TV someone put out for trash.
Hi Sperho, Oops I made factor of 10 mistake last night.
So at 900K the wire radiates at (500 W/m^2) * 3^4.. about 40kW/m^2 (The 300 K walls make only a small correction, 1 part in 81 ~1%) then 0.25 mm * pi =~ 0.75 mm x 30mm (1 foot) =~ 22 mm^2 = 22E-6m^2 from which I get about 0.9 watts. Of course once it gets to the point where 1/2 the heat goes away by copper conduction I can no longer can treat the wire as being at a single temperature. (then things get harder.. maybe just better to do the measurement.)
George H.
Go out and buy a lotto ticket. Report back the numbers.
That sounds more plausible.
Or simulate it, but that's too much like real work. Maybe I'll "assign" it to a fellow who's learning NASTRAN thermal modelling if I can sucker ^H^H^H convince him to do it.
--sp
Jackpot!
What do you need _another_ TV for?
--sp
Nah, for a not-so-vital piece of equipment, i.e. one you can do without and that won't burn down your house, try replacing the fuse first. If it blows again, then troubleshoot.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Thats been my rule for about 55 years. I am glad someone agrees with me. :-Z And if you only use the SAME SIZE fuse it will only blow again just like the first one with no geat damage if there really is a problem..
-- John G
Fuses cost money. A quick DMM ohms reading that shows near zero to ground means don't waste the money. Why not, it's already open after all.
Anyway, it's moot now.
You probably refer to the solar radiation balance: Earth gets the solar irradiation across the sunlit half, and re-emits it from the entire surface. If we assume perfect emissivity (Earth as a black body), the equation is
S pi Re^2 = 4 pi Re^2 sigma T^4
where S is solar irradiation (1367 W/m2), Re is Earth radius, sigma is Stefan-Boltzmann constant, 5.6703725e-08 kg / K^4 s^3, and T is the equilibrium temperature.
Interestingly, all the constants for this calculation are known to my favorite 'units' program available in all Linux distros: S is solarluminosity / 4 pi au2 where au is the astronomical unit, or Earth orbit mean radius, and sigma is known as 'stefanboltzman'.
From that we get T^4 = solarluminosity / (16 pi au2 stefanboltzmann), i.e. T = 278.7 K, i.e. 5 degrees Celsius or 41F.
Sadly, Mars orbit is significantly larger (between 1.38 and 1.67 au, so Mars temperature is much lower: taking an average of 1.52 au, we get T =
226K or approximately -50 (both F and C :). Whoever visits Mars first better take warm underwear.Venus on the other hand is toasty: at its 0.72au orbit T = 328K (55C/131F) Of course we know that the actual surface temperature on Venus is 735K, because Venus is definitely NOT a black body. It is an anomaly though--- other planets are much closer to the black body equilibrium temperature.
Obviously, its cloud surface is that temperature -- if not less given the very low albedo. All them clouds make for some crazy insulation though! Geothermal (athenothermal..???) heating, and what little visible light reaches the surface (comparable to heavy overcast clouds on Earth, IIRC?), keep the planet inside toasty.
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
I've been using Linux, exclusively for over ten years, and never knew that was there.
Great!
You discover something new every day.
--
"Design is the reverse of analysis"
(R.D. Middlebrook)
There may be others lurking about. Former sub nuc here, even interviewed with HGR back in the day. Been out of the business for a loooong time, though. And there's the NNPI issue...
It gets better---someone ported it to Android, too---I use it there a lot even though the UI is really old-school.
BTW, I actually prefer 'units' to all the GUI-based programs like 'convert' because it parses entire expressions: a couple of my favorite ones are:
the above 'black-body' equilibrium temperature for Earth
(solarluminosity / 16 pi au2 stefanboltzmann)^0.25
what fraction of solar mass did the Sun lose in the thermonuclear fusion since it started up 4.5 billion years ago:
(solarluminosity 4.5 billion years / c2)/ solarmass
It is amzazing that the result is just such a tiny number (3e-4). I guess it's reassuring that we aren't running out :)
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