12 May
2006
12 May
'06
3:07 p.m.
I need some help from those who are a lot better than I in hardware design...
The problem is I need to use a PC power supply (AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a 20-watt
power resistor of 1.5 ohms to keep the critter happy. "Bare minimum" is
15W, and I could squeak by with that if I wire the fan to the 5V line
instead of the 12V... but even when I'm expected to perform a "miracle" I
like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep 20-watt
power resistors in my back pocket. Had I a week, I'd just order the right
tool for the job - I don't have that luxury. ;-)
I was thinking I *might* be able to cobble up enough lower-end power
resistors & figure out how to stuff 'em together to draw 15w+ of power, but
then I thought:
What if I took an older 5V CPU (say... an 80486) and wired 'er up to just
Vcc & Ground - how much power would that use? [[ I've started some google
searches & I will continue, but I was hoping others here would have better
ideas than my lame-azz neurons & google so far ]]
I could also wire-wrap all the address/data lines to Vcc if that would add
a enough extra current draw to make 'er worth my while...
For those who are in lust with the "older, but still plentiful" CPUs like
that, then turn away now, you didn't see this, I was never here."
;-)
Any ideas will be most appreciated!
Thanks!
Roger "Merch" Merchberger
12 May
12 May
4:08 p.m.
On Friday 12 May 2006 03:07 pm, Roger Merchberger wrote:
I need some help from those who are a lot better than
I in hardware
design...
The problem is I need to use a PC power supply (AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a 20-watt
power resistor of 1.5 ohms to keep the critter happy. "Bare minimum" is
15W, and I could squeak by with that if I wire the fan to the 5V line
instead of the 12V... but even when I'm expected to perform a "miracle" I
like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep 20-watt
power resistors in my back pocket. Had I a week, I'd just order the right
tool for the job - I don't have that luxury. ;-)
I remember reading somewhere that taking one or several 12V light bulbs of the
automotive persuation and running them off the +5 supply would often work in
this situation. Got a junkyard nearby? :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
4:26 p.m.
What if I took an older 5V CPU (say... an 80486) and
wired 'er up to just
Vcc & Ground - how much power would that use? [[ I've started some google
searches & I will continue, but I was hoping others here would
have better
ideas than my lame-azz neurons & google so far ]]
1st, I assume that you won't leave any input pins "floating" - if you
do the
results are somewhat unpredictable (from no effect to more than "somewhat
glowing"!*)
* I had one dx4 overdrive chip self-destruct with one tiny (about 0.1"
square) part of
it glowing white hot ... never did find out why :-(
2nd, If unclocked the results are also difficult to predict - but the
probability is
that the consumption will be very low indeed (just as overclocking increases
power
usage).
Andy
8:10 p.m.
At 09:26 PM 5/12/2006 +0100, you wrote:
I think he should just use some LERs*. Or perhaps a SED* or two.
LER: Light-emitting resistor- ohm's law has been BROKEN.
SED: Smoke-emitting diode. See LER.
[Philosophy] What garlic is to food, insanity is to art. --anon.
fortune (revealed to me on 7.3.95)
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com (remove "nospam") N9QQB (amateur radio)
"HEY YOU" (loud shouting) WEB ADDRESS http//www.mixweb.com/tpeters
43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square
EN53wc
WAN/LAN/Telcom Analyst, Tech Writer, MCP, CCNA, Registered Linux User 385531
What if I took
an older 5V CPU (say... an 80486) and wired 'er up to just
Vcc & Ground - how much power would that use? [[ I've started some google
searches & I will continue, but I was hoping others here would
have better
ideas than my lame-azz neurons & google so far ]]
1st, I assume that you won't leave any input pins "floating" - if you
do the
results are somewhat unpredictable (from no effect to more than "somewhat
glowing"!*)
* I had one dx4 overdrive chip self-destruct with one tiny (about 0.1"
square) part of
it glowing white hot ... never did find out why :-(
2nd, If unclocked the results are also difficult to predict - but the
probability is
that the consumption will be very low indeed (just as overclocking increases
power
usage).
Andy
9:56 p.m.
MTBF: an LER has a very short expected service life (since its in the
process of burning up).
At 01:16 AM 5/13/2006 +0100, you wrote:
[Oops] "Who the hell wants to hear actors talk?" --Harry Warner of
Warner Brothers, 1925
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com (remove "nospam") N9QQB (amateur radio)
"HEY YOU" (loud shouting) WEB ADDRESS http//www.mixweb.com/tpeters
43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square
EN53wc
WAN/LAN/Telcom Analyst, Tech Writer, MCP, CCNA, Registered Linux User 385531
LER:
Light-emitting resistor- ohm's law has been BROKEN.
How does this differ from a light bulb, or indeed a red-hot heating element?
-tony 
13 May
13 May
12:02 a.m.
On 5/12/2006 at 8:56 PM Tom Peters wrote:
MTBF: an LER has a very short expected service life
(since its in the
process of burning up).
I like SDC*s myself. More spectacular.
--Chuck
*SDC=self-destroying capacitor. Those old steel-jacket mil-spec units
sealed with epoxy could be classified as weaponry.
12 May
12 May
4:29 p.m.
Roger Merchberger wrote:
I need some help from those who are a lot better than
I in hardware
design...
The problem is I need to use a PC power supply (AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a
20-watt power resistor of 1.5 ohms to keep the critter happy. "Bare
minimum" is 15W, and I could squeak by with that if I wire the fan to
the 5V line instead of the 12V... but even when I'm expected to
perform a "miracle" I like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep
20-watt power resistors in my back pocket. Had I a week, I'd just
order the right tool for the job - I don't have that luxury. ;-)
I was thinking I *might* be able to cobble up enough lower-end power
resistors & figure out how to stuff 'em together to draw 15w+ of
power, but then I thought:
What if I took an older 5V CPU (say... an 80486) and wired 'er up to
just Vcc & Ground - how much power would that use? [[ I've started
some google searches & I will continue, but I was hoping others here
would have better ideas than my lame-azz neurons & google so far ]]
Do you have a AT motherboard to go with the power supply?
If so, you can just plug it in as the load, as long as it leaves
you enough of the 12 Volt current available.
If you don't have one, check out the local thrift stores.
(Unless you really are stuck to using that particular PS).
You may end up with a 386, 486, etc., but it should still have
a 12V line. Why dink around with making a smoke generator
out of a PS when you can bypass the problem for $5.00 or so?
Don't limit yourself to PC cases, these places often have
external disk/CD drives also. These should also have 12V
line, iirc.
Also look in their boxes of wall warts. Sometimes you
will find something with the exact voltage/current
requirements.
I could also wire-wrap all the address/data lines to
Vcc if that would
add a enough extra current draw to make 'er worth my while...
Probably just generate a lot of smoke.
Unless you have the clock running, I don't think it will
use very much power at all. Most of the power in a CPU
is used because of the clock transitions.
For those who are in lust with the "older, but
still plentiful" CPUs
like that, then turn away now, you didn't see this, I was never here."
;-)
Any ideas will be most appreciated!
5:04 p.m.
On Fri, 12 May 2006, Roger Merchberger wrote:
I need some help from those who are a lot better than
I in hardware design...
certainly not me
The problem is I need to use a PC power supply
(AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a 20-watt
power resistor of 1.5 ohms to keep the critter happy. "Bare minimum" is
15W, and I could squeak by with that if I wire the fan to the 5V line
instead of the 12V... but even when I'm expected to perform a "miracle" I
like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep 20-watt
power resistors in my back pocket. Had I a week, I'd just order the right
tool for the job - I don't have that luxury. ;-)
For temporary loads to check power supplies, I use automobile headlights.
For a 5V load, I use a 6v headlight (usedta be common)
They provide enough load, and even light up the workspace.
5:12 p.m.
Most people throw out a dual filament (high and low beam) headlight when
either filament burns out. Save one for load testing. Or go to auto
repair shops and ask them to save you a bulb that still has one working
filament.
If a used discarded headlight is too expensive, and you need something
even cheaper, . . .
How much power does a ST4096 draw?
5:29 p.m.
New subject: Using modern PSUs to run old hardware
Friday, May 12, 2006, 9:07:55 PM, you wrote:
The problem is I need to use a PC power supply
(AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
That reminds me of some troubles I've had (or still have) replacing a
dead PSU in a vintage 4D/20 or 4D/25 ("SGI Personal Iris"). I've cut
out the old exsiting PSU and rewired an old switching PC supply in an
appropriate manner. Without drives the frankenIRIS works as expected,
but as soon as there is a drive attached to the internal power circuit
I end up getting a more or less purple display and a machine hanging
during POST. Well, time to get a 300-400W PSU I guess, as there is
probably a line running with less than enough power supplied to it by
the cheap PC PSU. It's old 5.25" SCSI drives, so probably 12V is the
source of the trouble... right?
--
Best regards,
Gerhard mailto:mail at g-lenerz.de
13 May
13 May
3:45 a.m.
New subject: Using modern PSUs to run old hardware
On Fri, 12 May 2006 23:29:12 +0200
Gerhard Lenerz <mail at g-lenerz.de> wrote:
but as soon as there is a drive attached to the
internal power circuit
I end up getting a more or less purple display and a machine hanging
during POST.
Maybe a problem with GND. You can get GND from the power connector,
from
the SCSI bus and from the enclosure. (The later is usually tied to GND
of the PSU.) Maybe you have a loop in there.
It's old 5.25" SCSI drives, so probably 12V
is the source of the
trouble... right?
Watch the voltages with a meter. If you own one, use an
oscilloscope to
look for ripple on the voltages.
I am interrested in your mod. I have a PI (4D30 IIRC) with dead PSU
slowly rotting in the basement...
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
12 May
12 May
8:05 p.m.
I need some help from those who are a lot better than I in hardware design...
The problem is I need to use a PC power supply (AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a 20-watt
power resistor of 1.5 ohms to keep the critter happy. "Bare minimum" is
15W, and I could squeak by with that if I wire the fan to the 5V line
instead of the 12V... but even when I'm expected to perform a "miracle" I
like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep 20-watt
power resistors in my back pocket. Had I a week, I'd just order the right
tool for the job - I don't have that luxury. ;-)
First thought : A car bulb. OK, they're designed for 12V, so will draw
less than the rated current at 5V (but maybe not that much less, bulbs do
approximate to constant current devices! [1]). You might get away, with
say a 21W car indicator bulb, or the 2 filaments of a 5W/21W tail and
brake light bulb in parallel.
[1] Am I the only person to remember what a Barretter is (even if I can't
remember the spelleing) ?
I was thinking I *might* be able to cobble up enough lower-end power
resistors & figure out how to stuff 'em together to draw 15w+ of power, but
then I thought:
What if I took an older 5V CPU (say... an 80486) and wired 'er up to just
Vcc & Ground - how much power would that use? [[ I've started some google
Less than you might think. Most of the power consumed by this sort of
chip goes into charging/discharging stray capacitance when signals switch
states. That's why the chips get hotter as the clock frequency rises.
WIth no clock, it'll not comsume that much power.
I could also wire-wrap all the address/data lines to
Vcc if that would add
a enough extra current draw to make 'er worth my while...
That's likely to burn the chip out if you're not careful!
-tony
8:07 p.m.
At 03:07 PM 5/12/2006 -0400, you wrote:
I need some help from those who are a lot better than I
in hardware design...
The problem is I need to use a PC power supply (AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a 20-watt
power resistor of 1.5 ohms to keep the critter happy. "Bare minimum" is
15W, and I could squeak by with that if I wire the fan to the 5V line
instead of the 12V... but even when I'm expected to perform a "miracle" I
like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep 20-watt
power resistors in my back pocket. Had I a week, I'd just order the right
tool for the job - I don't have that luxury. ;-)
I was thinking I *might* be able to cobble up enough lower-end power
resistors & figure out how to stuff 'em together to draw 15w+ of power,
but then I thought:
What if I took an older 5V CPU (say... an 80486) and wired 'er up to just
Vcc & Ground - how much power would that use? [[ I've started some google
searches & I will continue, but I was hoping others here would have better
ideas than my lame-azz neurons & google so far ]]
I could also wire-wrap all the address/data lines to Vcc if that would add
a enough extra current draw to make 'er worth my while...
For those who are in lust with the "older, but still plentiful" CPUs like
that, then turn away now, you didn't see this, I was never here."
;-)
1. A CPU with nothing else connected will have the address and data lines
(and clock) inputs floating all over the place, and will probably lock up
immediately, then melt. You, I'm sure, know that, but a few others have
suggested it and this is for their benefit.
2. Three AMPS? Yikes. I've been able to use classic AT style power supplies
with an old hard drive plugged in. The +12 isn't quite as stiff as if the
+5 is loaded down more significantly, but yowzers, 3 amps? That's quite a
bit. This was all covered in an issue of QST magazine sometime last year.
The web site doesn't keep issues so the article itself isn't directly
available on line, but a search of arrl.org might turn up something.
The upshot of the article was that PC power supplies aren't the best for
running radios, due to the huge over-rating that's common (specsmanship,
i.e. untruth in advertising) and other factors.
73 es HTH,
Tom, N9QQB
[Government]We contend that for a nation to try to tax itself into
prosperity is like a man standing in a bucket and trying to lift
himself up by the handle. --Winston Churchill
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com (remove "nospam") N9QQB (amateur radio)
"HEY YOU" (loud shouting) WEB ADDRESS http//www.mixweb.com/tpeters
43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square
EN53wc
WAN/LAN/Telcom Analyst, Tech Writer, MCP, CCNA, Registered Linux User 385531
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days inactive
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13 comments
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andyh＠andyh-rayleigh.freeserve.co.uk -
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jkunz＠unixag-kl.fh-kl.de -
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