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Phil Allison
Guest
Sun Aug 14, 2011 2:54 am
"Rich Grise"
Quote:
Yabbut, I was responding to "Nobody", who wrote,
"SMPS have a far greater variety of possible (and plausible) failure
modes."
I was just hoping he'd list them or cite an example or something.
** You fucking thick or sumtin' ?
Every part in a SMPS adaptor is likely to fail - some likely to produce a
loss of isolation from the AC supply.
The comparison is with a simple, DC adaptor that only has three parts.
FYI
1. A 50/60Hz fail safe transformer.
2. A bridge rectifier.
3. A filter electro.
..... Phil
Phil Allison
Guest
Sun Aug 14, 2011 3:44 am
"Bill Bowden"
Quote:
"Complexity is the enemy of reliability".
SMPS have a far greater variety of possible (and plausible) failure
modes.
Sure, but they only cost $2 at a swap meet.
** Irrelevant crapology.
.... Phil
Bill Bowden
Guest
Sun Aug 14, 2011 5:32 am
On Aug 12, 10:58 pm, Nobody <nob...@nowhere.com> wrote:
Quote:
On Fri, 12 Aug 2011 20:22:01 -0700, Bill Bowden wrote:
The modern switcher types mostly regulate very nicely.
** Damn shame they are in almost every other way dangerous piles of shit.
... Phil
Why are they dangerous? I have one plugged in 24/7. Been running for a
couple years.
"Complexity is the enemy of reliability".
SMPS have a far greater variety of possible (and plausible) failure
modes.
Sure, but they only cost $2 at a swap meet. Who cares how complex they
are as long as they don't burn the house down?
-Bill
John Tserkezis
Guest
Sun Aug 14, 2011 7:20 am
Rich Grise wrote:
Quote:
Yabbut, I was responding to "Nobody", who wrote,
"SMPS have a far greater variety of possible (and plausible) failure
modes."
I was just hoping he'd list them or cite an example or something.
You don't have to. The fact it has more parts, by that very nature
means there are more points of failure. We're generalising there,
there's no need to specify numbers, just the point that in general, more
parts = more failures.
But it's more complicated than that. It comes down to the design.
With some designs with low component counts, the entire operation may
hinge on a single component. One failure will bring it to its knees,
rather than "half fail" where some things may still work.
This you *can't* generalise on, because you can't generalise on designs
you don't have statistics on.
--
If I had anything witty to say, I wouldn't put it here.
Rich Grise
Guest
Sun Aug 14, 2011 8:53 am
John Tserkezis wrote:
Quote:
Rich Grise wrote:
Yabbut, I was responding to "Nobody", who wrote,
"SMPS have a far greater variety of possible (and plausible) failure
modes."
I was just hoping he'd list them or cite an example or something.
You don't have to. The fact it has more parts, by that very nature
means there are more points of failure. We're generalising there,
there's no need to specify numbers, just the point that in general, more
parts = more failures.
Well, I'm no theoretical physicist or rocket scientist, but I do know
that to determine failure rates of a particular design, you have to
count actual failures per actual number of units, and I'm sorry, but
to do that in real life you need numbers.
Hope This Helps!
Rich
John Tserkezis
Guest
Sun Aug 14, 2011 10:29 am
Rich Grise wrote:
Quote:
Well, I'm no theoretical physicist or rocket scientist, but I do know
that to determine failure rates of a particular design, you have to
count actual failures per actual number of units, and I'm sorry, but
to do that in real life you need numbers.
You're talking about more specific numbers, the OP was talking very
general around-about sort of kinda you get what I mean.
Also, I have to nit-pick on your statement that you have to count
failures. It defeats the purpose doesn't it? True, once you count the
failures verses the live units, you get an absolute correct count (at
least at that point in the life cycle). That's nice, but at this point,
you're pretty much telling everyone what they already know.
The point here is to PREDICT failures. And THAT is much more difficult
to do. It involves black magic and voodoo mathematics, and depending on
who you ask, the phase of the moon too.
The switchmode design / component count issue having higher failure
rates than an inductive transformer is a predictive model. Not an
accurate one mind you, but predictive none the less.
--
You can tune a guitar, but you cant tuna fish.
John Fields
Guest
Mon Aug 15, 2011 3:23 pm
On Sun, 14 Aug 2011 20:29:12 +1000, John Tserkezis
<jt_at_techniciansyndrome.org.invalid> wrote:
You can tune a guitar, but you cant tuna fish.
---
Parrot 1: "What's that stink?"
Parrot 2: "That perch you're standing on."
--
JF
Rich Grise
Guest
Tue Aug 16, 2011 10:22 pm
John Fields wrote:
Quote:
On Sun, 14 Aug 2011 20:29:12 +1000, John Tserkezis
You can tune a guitar, but you cant tuna fish.
You can cream asparagus, but you can't pea soup.
Quote:
Parrot 1: "What's that stink?"
Parrot 2: "That perch you're standing on."
Huh? What's this supposed to mean?
I like Jake's quickie from 2.5 Men: "Two muffins are baking in
the oven. One muffin says, "Boy, sure is hot in here." The other
muffin says, "Oh, my God! A talking muffin!""
Wanna hear the world's worst joke?
Q: Why do cows wear bells?
A: Because their horns don't work.
Cheers!
Rich
Phil Allison
Guest
Tue Aug 16, 2011 10:30 pm
"Rich Grise"
Quote:
Wanna hear the world's worst joke?
Q: Why do cows wear bells?
A: Because their horns don't work.
** Did you hear about the cow they thought was a genius ?
Well, she was out standing in her field ...
..... Phil
John Fields
Guest
Tue Aug 16, 2011 11:32 pm
On Tue, 16 Aug 2011 15:22:52 -0700, Rich Grise
<richg_at_example.net.invalid> wrote:
Quote:
John Fields wrote:
On Sun, 14 Aug 2011 20:29:12 +1000, John Tserkezis
You can tune a guitar, but you cant tuna fish.
You can cream asparagus, but you can't pea soup.
Parrot 1: "What's that stink?"
Parrot 2: "That perch you're standing on."
Huh? What's this supposed to mean?
---
Two parrots are sitting on a perch.
One says: "Do you smell fish?
--
JF
John Fields
Guest
Tue Aug 16, 2011 11:37 pm
On Wed, 17 Aug 2011 08:30:24 +1000, "Phil Allison" <phil_a_at_tpg.com.au>
wrote:
Quote:
"Rich Grise"
Wanna hear the world's worst joke?
Q: Why do cows wear bells?
A: Because their horns don't work.
** Did you hear about the cow they thought was a genius ?
Well, she was out standing in her field ...
---
Did you hear about the woman who ate a doorknob?
It turned her stomach.
--
JF
Bill Bowden
Guest
Wed Aug 17, 2011 2:32 am
On Aug 16, 3:22 pm, Rich Grise <ri...@example.net.invalid> wrote:
Quote:
John Fields wrote:
On Sun, 14 Aug 2011 20:29:12 +1000, John Tserkezis
You can tune a guitar, but you cant tuna fish.
You can cream asparagus, but you can't pea soup.
Parrot 1: "What's that stink?"
Parrot 2: "That perch you're standing on."
Huh? What's this supposed to mean?
I like Jake's quickie from 2.5 Men: "Two muffins are baking in
the oven. One muffin says, "Boy, sure is hot in here." The other
muffin says, "Oh, my God! A talking muffin!""
Wanna hear the world's worst joke?
Q: Why do cows wear bells?
A: Because their horns don't work.
Cheers!
Rich
I went to a museum and asked how old the dinosaur bones were, and the
attendant said they were 65,000,013 years old. So, I asked how
technology could measure ages to such accuracy of 13 years, and he
said:
"Well, I've been working here for 13 years, and when I started they
told me those bones were 65 million years old."
-Bill
Guest
Thu Aug 18, 2011 10:14 pm
On Sun, 14 Aug 2011 10:55:56 +1000, John Tserkezis
<jt_at_techniciansyndrome.org.invalid> wrote:
Quote:
My keyboard has an F1 key. Where is the NASCAR key?
Your keyboard is obviously a racing keyboard. That's why there is no
NASCAR key.
Eric
Kaz Kylheku
Guest
Tue Aug 30, 2011 6:04 am
On 2011-08-07, Orson Cart <ex-privat_at_parts.org> wrote:
Quote:
So are these things designed to give only the correct voltage at
rated load?
No, these things have capacitors which charge to a peak voltage, which is what
you're measuring with your high-impedance multimeter.
You're forgetting about peak versus RMS voltages.
For instance, to make a 12V wall bug, we will take a 10:1 transformer, which
gives us 12V AC RMS. This will rectify to a fluctuating DC, which is also 12V
RMS.
That fluctuating DC will charge the internal capacitor to about 17V: its peak
voltage (12 / 0.707).
Quote:
I conjecture that there is a lot of resistance in the
smoothing circuit.
The wall bug would have this behavior even if it were made up out of
superconductive components. It contains reactances; it is not a battery with an
internal resistance. That model does not apply.
The internal resistance of a battery-like voltage source will reduce voltage in
proportion to the current demand (Ohm's law).
The wall bug's voltage drop is different. With increasing loads, the average
of its increasingly rippling voltage will go down toward the RMS value, but
near the RMS value, it should stiffen up and show a different voltage drop
behavior from there toward zero ohms.
John Fields
Guest
Tue Aug 30, 2011 11:58 am
On Tue, 30 Aug 2011 04:04:54 +0000 (UTC), Kaz Kylheku
<kaz_at_kylheku.com> wrote:
Quote:
On 2011-08-07, Orson Cart <ex-privat_at_parts.org> wrote:
So are these things designed to give only the correct voltage at
rated load?
No, these things have capacitors which charge to a peak voltage, which is what
you're measuring with your high-impedance multimeter.
You're forgetting about peak versus RMS voltages.
For instance, to make a 12V wall bug, we will take a 10:1 transformer, which
gives us 12V AC RMS. This will rectify to a fluctuating DC, which is also 12V
RMS.
That fluctuating DC will charge the internal capacitor to about 17V: its peak
voltage (12 / 0.707).
I conjecture that there is a lot of resistance in the
smoothing circuit.
The wall bug would have this behavior even if it were made up out of
superconductive components. It contains reactances; it is not a battery with an
internal resistance. That model does not apply.
The internal resistance of a battery-like voltage source will reduce voltage in
proportion to the current demand (Ohm's law).
The wall bug's voltage drop is different. With increasing loads, the average
of its increasingly rippling voltage will go down toward the RMS value, but
near the RMS value, it should stiffen up and show a different voltage drop
behavior from there toward zero ohms.
---
Even after having said all that, the fact remains that because of its
internal resistance, an unregulated wall-wart's output voltage is
specified for a given load.
--
JF
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