| View previous topic :: View next topic |
| Author |
Message |
John Larkin
Guest
|
 Posted: Sat Jul 26, 2008 9:49 pm Post subject: Re: 0805 size high power resistors, 250mW ok on FR-4? |
 |
|
On Sat, 26 Jul 2008 08:21:18 -0700, Joerg
<notthisjoergsch@removethispacbell.net> wrote:
[quote]John Larkin wrote:
On Fri, 25 Jul 2008 15:36:49 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
John Larkin wrote:
On Fri, 25 Jul 2008 14:26:18 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
John Larkin wrote:
On Wed, 23 Jul 2008 09:59:26 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
Hello All,
Got a circuit where in hindsight the client decided they need >10 times
the juice than initially spec>d. This was truly unforeseen for them and
we have to make it work at least for a proto series. Of course, now all
those 0805 resistors in the power path would exceed their usual 1/8W
spec. Found these at 1/3W:
http://www.susumu.co.jp/english/pdf/products-j01-07.pdf
I plan to run them around 200-250mW. Was expecting those to be really
tall to vent off some heat but they are surprisingly flat, only 0.4mm
high. Will this become a heat problem on FR-4 for stuff that can run
24/7? Any experience?
Can I interest you in 0402 at 10 watts? Or 0505 at 50 watts?
http://www.emct.com/microwavepassivecomponents-a43445.html
Ouch! That ought to do it for an impressive meltdown procedure on FR4.
Reminds me of a tube in a ceramic socket on phenolic. I was still a kid,
blissfully unaware of the limitations of some materials. Transistors
were very expensive in Germany so I built most stuff from salvaged
tubes, plucked out of radios and TV sets. Well, this thing worked for
months. Then one fine day there was fireworks, hissing and smoke. The
ceramic socket including tube had fallen through the charred hole that
had developed. Now I knew where that faint "amperage smell" was coming
from. Luckily the plate connector was up top and the tube fell in, but
didn>t tip over. Cuz I had "economized" on the power supply and ran
straight from 230V mains into a voltage doubler. The fuse was, ahem,
home made.
My first ever job interview, I made the comment that I generally
preferred tubes (which I got free) to transistors, because transistors
were too easy to blow up. The prig said "that won>t do" and didn>t
hire me. Next interview, I said the same thing and that guy laughed
and did hire me. I designed about $100M of stuff for the second guy.
Similar things happen to consultants. Sometimes people present a task,
then ask whether I am versed in VHDL, Cadence and all that. I often tell
them "No, but a chip design wouldn>t make sense here, we can do that at
lower cost with off-the-shelf parts". Sometimes they walk away. The
companies of those who do are usually not heard of much anymore. Some of
them keep burning an enormous amount of cash until their VCs turn off
the spigot. The sad cases are where I could have really helped them with
$50-100K in cost, they decline, keep trying on their own, blow through
another few million bucks and then kablouie.
I had that same experience with Metricon. I had a bog simple, cheap,
proven way to do what they needed. They had a complex mess, but said
it didn>t matter because "silicon is free." Remember Metricon?
These guys?
http://www.metricon.com/
[/quote]
No. They were in Silicon Valley. They started as an RF electric-meter
reading company, staffed by a bunch of ham-radio types. The meter they
designed was too expensive for any utilities to buy (geez, I only
wanted a buck a meter in royalties) so they hopped on the Internet
bandwagon and migrated their mesh technology into Ricocet.
http://en.wikipedia.org/wiki/Ricochet_%28internet_service%29
http://www.hamradio-online.com/1996/jan/metricom.html
http://ricochet.us/
The guru was
http://en.wikipedia.org/wiki/Paul_Baran
and the prez, when I was involved, was Bob Dilworth, formerly the head
of Zenith Data Systems, the early laptop pioneer.
Burning hulks everywhere.
John |
|
| |
|
 Back to top |
Joerg
Guest
|
| Posted: Sun Jul 27, 2008 12:52 am Post subject: Re: 0805 size high power resistors, 250mW ok on FR-4? |
|
|
John Larkin wrote:
[quote]On Sat, 26 Jul 2008 08:21:18 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
John Larkin wrote:
On Fri, 25 Jul 2008 15:36:49 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
John Larkin wrote:
On Fri, 25 Jul 2008 14:26:18 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
John Larkin wrote:
On Wed, 23 Jul 2008 09:59:26 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:
Hello All,
Got a circuit where in hindsight the client decided they need >10 times
the juice than initially spec>d. This was truly unforeseen for them and
we have to make it work at least for a proto series. Of course, now all
those 0805 resistors in the power path would exceed their usual 1/8W
spec. Found these at 1/3W:
http://www.susumu.co.jp/english/pdf/products-j01-07.pdf
I plan to run them around 200-250mW. Was expecting those to be really
tall to vent off some heat but they are surprisingly flat, only 0.4mm
high. Will this become a heat problem on FR-4 for stuff that can run
24/7? Any experience?
Can I interest you in 0402 at 10 watts? Or 0505 at 50 watts?
http://www.emct.com/microwavepassivecomponents-a43445.html
Ouch! That ought to do it for an impressive meltdown procedure on FR4.
Reminds me of a tube in a ceramic socket on phenolic. I was still a kid,
blissfully unaware of the limitations of some materials. Transistors
were very expensive in Germany so I built most stuff from salvaged
tubes, plucked out of radios and TV sets. Well, this thing worked for
months. Then one fine day there was fireworks, hissing and smoke. The
ceramic socket including tube had fallen through the charred hole that
had developed. Now I knew where that faint "amperage smell" was coming
from. Luckily the plate connector was up top and the tube fell in, but
didn>t tip over. Cuz I had "economized" on the power supply and ran
straight from 230V mains into a voltage doubler. The fuse was, ahem,
home made.
My first ever job interview, I made the comment that I generally
preferred tubes (which I got free) to transistors, because transistors
were too easy to blow up. The prig said "that won>t do" and didn>t
hire me. Next interview, I said the same thing and that guy laughed
and did hire me. I designed about $100M of stuff for the second guy.
Similar things happen to consultants. Sometimes people present a task,
then ask whether I am versed in VHDL, Cadence and all that. I often tell
them "No, but a chip design wouldn>t make sense here, we can do that at
lower cost with off-the-shelf parts". Sometimes they walk away. The
companies of those who do are usually not heard of much anymore. Some of
them keep burning an enormous amount of cash until their VCs turn off
the spigot. The sad cases are where I could have really helped them with
$50-100K in cost, they decline, keep trying on their own, blow through
another few million bucks and then kablouie.
I had that same experience with Metricon. I had a bog simple, cheap,
proven way to do what they needed. They had a complex mess, but said
it didn>t matter because "silicon is free." Remember Metricon?
These guys?
http://www.metricon.com/
No. They were in Silicon Valley. They started as an RF electric-meter
reading company, staffed by a bunch of ham-radio types. The meter they
designed was too expensive for any utilities to buy (geez, I only
wanted a buck a meter in royalties) so they hopped on the Internet
bandwagon and migrated their mesh technology into Ricocet.
http://en.wikipedia.org/wiki/Ricochet_%28internet_service%29
[/quote]
Quote "Ricochet sent its Denver based customers an email at night on
March 28th 2008, that service will cease as of March 29th 2008."
Yikes! Talking about customer valuation. Drop the ball and run.
[quote]
http://www.hamradio-online.com/1996/jan/metricom.html
[/quote]
Quote "Overall, Ricochet is the only consumer priced, mass market, high
speed, wireless data network that enables you to send unlimited data."
ROFL! I can just picture what>ll happen when everyone is online and you
want to download that 4MB PDF datasheet.
[quote]http://ricochet.us/
The guru was
http://en.wikipedia.org/wiki/Paul_Baran
and the prez, when I was involved, was Bob Dilworth, formerly the head
of Zenith Data Systems, the early laptop pioneer.
Burning hulks everywhere.
[/quote]
Pretty sad. This repeater technology has a hard time. Companies try to
push it via protocols such as Zigbee but in order to make that work
customers usually can>t start out small, you have to have critical mass.
Data volumes are low and when a node at a critical juncture goes down a
whole chunk of the network becomes orphaned.
In ham radio packet transmission is rather successful and very useful in
emergencies. But that>s because ham groups can mobilize a large pool of
motivated volunteers very fast and data volumes are low.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM. |
|
| |
|
| Back to top |
John Larkin
Guest
|
| Posted: Sun Jul 27, 2008 2:40 am Post subject: Re: 0805 size high power resistors, 250mW ok on FR-4? |
|
|
On Sat, 26 Jul 2008 12:52:01 -0700, Joerg
<notthisjoergsch@removethispacbell.net> wrote:
[quote]These guys?
http://www.metricon.com/
No. They were in Silicon Valley. They started as an RF electric-meter
reading company, staffed by a bunch of ham-radio types. The meter they
designed was too expensive for any utilities to buy (geez, I only
wanted a buck a meter in royalties) so they hopped on the Internet
bandwagon and migrated their mesh technology into Ricocet.
http://en.wikipedia.org/wiki/Ricochet_%28internet_service%29
Quote "Ricochet sent its Denver based customers an email at night on
March 28th 2008, that service will cease as of March 29th 2008."
Yikes! Talking about customer valuation. Drop the ball and run.
http://www.hamradio-online.com/1996/jan/metricom.html
Quote "Overall, Ricochet is the only consumer priced, mass market, high
speed, wireless data network that enables you to send unlimited data."
ROFL! I can just picture what>ll happen when everyone is online and you
want to download that 4MB PDF datasheet.
http://ricochet.us/
The guru was
http://en.wikipedia.org/wiki/Paul_Baran
and the prez, when I was involved, was Bob Dilworth, formerly the head
of Zenith Data Systems, the early laptop pioneer.
Burning hulks everywhere.
Pretty sad. This repeater technology has a hard time. Companies try to
push it via protocols such as Zigbee but in order to make that work
customers usually can>t start out small, you have to have critical mass.
Data volumes are low and when a node at a critical juncture goes down a
whole chunk of the network becomes orphaned.
In ham radio packet transmission is rather successful and very useful in
emergencies. But that>s because ham groups can mobilize a large pool of
motivated volunteers very fast and data volumes are low.
[/quote]
Oops, sorry, I spelled the name wrong, as usual. Metricom, not
Metricon.
Another example of mass insanity.
John |
|
| |
|
| Back to top |
David Tweed
Guest
|
| Posted: Mon Jul 28, 2008 6:29 am Post subject: Re: 0805 size high power resistors, 250mW ok on FR-4? |
|
|
Joerg wrote:
[quote]David Tweed wrote:
Joerg wrote:
Similar things happen to consultants. Sometimes people present a
task, then ask whether I am versed in VHDL, Cadence and all that. I
often tell them "No, but a chip design wouldn>t make sense here, we
can do that at lower cost with off-the-shelf parts". Sometimes they
walk away. The companies of those who do are usually not heard of
much anymore. Some of them keep burning an enormous amount of cash
until their VCs turn off the spigot. The sad cases are where I could
have really helped them with $50-100K in cost, they decline, keep
trying on their own, blow through another few million bucks and then
kablouie.
I>m beginning to suspect that, in many cases, that (the last sentence)
is in fact the whole point of the operation. The high-level technical
people may or may not believe in the product/technology being developed,
but the executives are just in it for the boondoggle, living high on the
hog for as long as the investor money lasts, then moving on to a
different
project.
Even the investors are not entirely unhappy with this situation --
they>re often looking for ways to take a loss without being too obvious
about it.
It>s just frustrating for the lower-level technical people who probably
don>t realize what>s going on and put a lot of good work into something
that just ends up in the dumpster. I once worked for a company where I
now firmly believe that this is what was (and may still be) going on.
Luckily none of my clients, many of whom are VC-financed, is like that.
They all want to make it happen and I am sure most of them will. There
is always going to be risk, as in "venture" :-)
[/quote]
None of my current clients is like that, either. It>s just that I>ve
seen a few organizations that just couldn>t possibly be that badly
managed by accident alone.
Now that I>m a full-time consultant, I have plenty of work from a fairly
diverse set of clients. I get paid straight time and materials, while
they take the risks and reap the rewards (or not). This suits me just
fine.
-- Dave Tweed |
|
| |
|
| Back to top |
|
