John Larkin wrote: > On Wed, 23 Jul 2008 09:59:26 -0700, Joerg > <notthisjoerg...@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:
>> 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?
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.
>>> 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:
>>> 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?
>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.
John Larkin wrote: > On Fri, 25 Jul 2008 14:26:18 -0700, Joerg > <notthisjoerg...@removethispacbell.net> wrote:
>> John Larkin wrote: >>> On Wed, 23 Jul 2008 09:59:26 -0700, Joerg >>> <notthisjoerg...@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:
>>>> 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?
>> 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.
>>> John Larkin wrote: >>>> On Wed, 23 Jul 2008 09:59:26 -0700, Joerg >>>> <notthisjoerg...@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:
>>>>> 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?
>>> 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 >$50-100K in cost, they decline, keep trying on their own, blow through >another few million bucks and then kablouie.
I had that same experience with Metricon. I had a bog simple, cheap, proven way to do what they needed. They had a complex mess, but said it didn't matter because "silicon is free." Remember Metricon?
>>Got a circuit where in hindsight the client decided they need >10 times >>the juice than initially spec'd. This was truly unforeseen for them and >>we have to make it work at least for a proto series. Of course, now all >>those 0805 resistors in the power path would exceed their usual 1/8W >>spec. Found these at 1/3W:
>>I plan to run them around 200-250mW. Was expecting those to be really >>tall to vent off some heat but they are surprisingly flat, only 0.4mm >>high. Will this become a heat problem on FR-4 for stuff that can run >>24/7? Any experience?
>Can I interest you in 0402 at 10 watts? Or 0505 at 50 watts?
Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" sp...@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On a sunny day (Fri, 25 Jul 2008 14:26:18 -0700) it happened Joerg <notthisjoerg...@removethispacbell.net> wrote in <dyrik.19049$N87.15...@nlpi068.nbdc.sbc.com>:
>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.
In the sixties, when working with these Ampex VR1000 quadruplex video recorders, http://www.lionlamb.us/quad/vr1000_1.jpg the recording head drivers were tubes, mounted upside down in a small box with a fan. Sometimes the fan stopped, and the alarm (some mechanical air flow sensor) did not always work, the tubes would un-solder themselves and fall out of the sockets to the bottom of the amp housing. The 2 cabinets on the left in the picture were also filled with tubes... The average working temperature in that place (we had several of those machines) was pretty high too.
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.
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > On Thu, 24 Jul 2008 10:18:26 GMT, Jan Panteltje
> <pNaonStpealm...@yahoo.com> wrote: > >On a sunny day (Wed, 23 Jul 2008 13:55:18 -0700) it happened John Larkin > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote in > ><au5f84drqafqn7u3nbnndn5nauiaue4...@4ax.com>:
> >>>Xcuse me, but would not a finger test show that too? That teh DACS were much > >>>hotter then the FPGA? > >>>I am not against modern tech, but 10k is a lot of money for something you > >>>can also do with a temp probe or your finger. > >>>;-)
> >>Consider a series of images, of the whole board and of regions, taken > >>at different clock rates. That tells us, very quickly, where the power > >>is going, and sometimes it's unexpected. It's very hard to quantify, > >>or even feel, the temperature of an 0603 resistor or a SOT-23 opamp, > >>and one board can have hundreds. If you stick a thermocouple to a > >>small part, you suck all the heat away. And the simple IR thermometers > >>have rotten spatial resolution.
> >>One of our VME boards can sell for more than the Flir cost. It's been > >>a great tool, sort of an instant thermal design review.
> >>It's also cool for troubleshooting. Suppose a power rail is collapsed. > >>You can often image the board and find the part that's hogging the > >>power. Or add another power supply, force a few amps, and image the > >>traces.
> >>And with the tax considerations, the net price is about half.
> >>John
> >OK, > >is that thing also capable of displaying real temperatures? > >I mean if you put a mouse cursor on say the FPGA, will it display '90C', > >or something? > >Or is it just relative as the colors show?
> Realtime, on the built-in lcd screen, you can read the temperature of > the center-screen bulls-eye, or of an averaged region. You can also > export an image to the PC and offline read the temperature of every > pixel, or plot profiles, or average regions. The only gotcha is that > you've got to be careful about emissivity.
> Correlation to temperature measured with thermocouples is very good, > within 1-2 C usually. We dab things with a black whiteboard marker if > we suspect the emissivity is low; that seems to work well. The > heatsink in my second image is shiny aluminum, so its indicated temp > is way off.
> Interestingly, most visually transparent things, like a plastic bag, > or glass, or ice/water, are black in the thermal IR. So it's difficult > to, say, put a window in a box to maintain air flow and peek internal > temps. The thinnest plastic film we could find at the supermarket is > about 50% density at these wavelengths. Human body heat patterns are > interesting.
> John
Scotch tape or Electrical tape also gets up to 95% emissivity as well. Yes looking inside of a box is a pain. Of course you always have to do sanity checks to validate your test setup.
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > On Thu, 24 Jul 2008 15:44:55 GMT, Jan Panteltje
> <pNaonStpealm...@yahoo.com> wrote: > >On a sunny day (Thu, 24 Jul 2008 08:22:52 -0700) it happened John Larkin > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote in > ><ir6h841050e1s5q7fdo8mq43d38bnm2...@4ax.com>:
> >>>OK, > >>>is that thing also capable of displaying real temperatures? > >>>I mean if you put a mouse cursor on say the FPGA, will it display '90C', > >>>or something? > >>>Or is it just relative as the colors show?
> >>Realtime, on the built-in lcd screen, you can read the temperature of > >>the center-screen bulls-eye, or of an averaged region. You can also > >>export an image to the PC and offline read the temperature of every > >>pixel, or plot profiles, or average regions. The only gotcha is that > >>you've got to be careful about emissivity.
> >OK, thank you for the elaborate explanation. > >I just looked up IR camera and found this nice FLIR application on youtube: > >http://www.youtube.com/watch?v=SJ-8yFgWt-c
