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Sherlock Ohms

The New Controller Just Wasn’t Cool

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Rob Spiegel
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Blogger
A simple solution
Rob Spiegel   11/20/2013 11:38:53 AM
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Here's yet another beautiful example of a Sherlock Ohms solution that is incredibly simple. 

Charles Murray
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Re: A simple solution
Charles Murray   11/20/2013 7:00:58 PM
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This is the kind of problem that causes engineers to search for weeks and examine every possibility, no matter how complex. Only an experienced engineer would have thought of something as simple as vent holes.

OLD_CURMUDGEON
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Platinum
Aaaaaaaaaaaaaaaaaah, YES! ... HEAT!
OLD_CURMUDGEON   11/21/2013 8:48:29 AM
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When ICs were becoming MORE popular in the late 60s, onward, one of the essential pieces of "test equipment" at all our engineering lab benches was at least one aerosol can of "cold".  The equipment designed was high-end, commercial grade radio communications gear.  It had to function from the environs of the Arctic cold to the sub-Saharan hot.  We could not risk heat prostration failures, since these chassis were a combination of solid-state & vacuum tube technology.  Additionally, since much of this equipment had to pass FCC certification, it was subjected to extensive environmental chamber testing while in full operation mode, whether receiving or transmitting signals.  Even w/ directed forced-air cooling, provisions were made for proper operation at the full specified operating temperature range.

tekochip
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Platinum
Re: Aaaaaaaaaaaaaaaaaah, YES! ... HEAT!
tekochip   11/21/2013 9:25:37 AM
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Freeze Mist.  I hate to say how much of that stuff we used to go through, and how much of it was used to defeat locked thermostats on a drafty factory floor, attempt cryogenics on insects or propel test tube stoppers.  At least the components were better by the time the EPA killed Freon in a can.
 
Really, think about how many component failures we had back then.  The fallout was so large that we used to burn-in components and systems.


OLD_CURMUDGEON
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Platinum
Re: Aaaaaaaaaaaaaaaaaah, YES! ... HEAT!
OLD_CURMUDGEON   11/21/2013 9:36:21 AM
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"Bathing" p.c. boards and simultaneously watching signals change drastically on the o-scopses!  Aaah! What fun!  Most of the ICs we used were plastic, commercial-grade devices, although in some critical applications we did use the more reliable ceramic DIP variant.  And, it was especially important to us since frequency drift was restricted to about 20 cycles / Mc. 

3drob
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Platinum
Re: Aaaaaaaaaaaaaaaaaah, YES! ... HEAT!
3drob   11/21/2013 9:50:54 AM
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The old style Freon freeze spray was awesome stuff.  The new spray's just don't cut it (stupid O'zone hole).  But don't forget pulling out the heat gun to "encourage"  problems to reveal themselves.

In the recent past, I've also used a FLIR (borrowed from another program) to actually see the parts that were running too hot.  Much faster and easier to get a quick snap-shot right after pulling a lid than instrumenting with a bank of thermocouples.

A good story, (but surprising because I was expecting the solution to start with "and then I had to hop on the next flight ..." ).

TRCSr
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Silver
Re: Aaaaaaaaaaaaaaaaaah, YES! ... HEAT!
TRCSr   11/21/2013 8:27:18 PM
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Yes, I used a lot of the spray Freon over the years of my carrer. In this case I just failed to give thought to heat being the source of the problem, mainly since both controllers were mounted in what I thought were nearly identical environments. It turned out that there was leakage nearer to the one that allowed the cooling air to be concentrated on that controller. Lesson learned!

Nancy Golden
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Platinum
Re: A simple solution
Nancy Golden   11/24/2013 7:01:52 PM
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"This is the kind of problem that causes engineers to search for weeks and examine every possibility, no matter how complex. Only an experienced engineer would have thought of something as simple as vent holes."

Until it happens once - then you never forget and overheating comes to the top of your list...I can't tell you how many times I have had to tell my son to quit covering the vents on any of the numerous electronic boxes that are common to any household from TVs to stereos etc. or to not use his laptop on the carpeting. Air circulation is your friend and covering vents with books or DVD cases is not a friendly act...


Freon was also standard on every tech bench in the old days. When I worked in product engineering - we also tested chips across temp. We were either forcing them cold with liquid nitrogen or burning them in. Spec sheets will tell you a chip's operating temperature tolerances but it's harder at the system level for the reasons stated in various comments. Keeping electronics cool is definately an issue that needs to be considered in every design from chip to chassis...


taimoortariq
User Rank
Gold
DebuggingI
taimoortariq   11/30/2013 11:02:28 PM
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I actually have had similar problems with the motor controllers, specially for the motors that have high current ratings and run on high load. The heating problem is the worst of them all. Ultimately, I ended up using huge heat sinks to solve my problem.

johnr
User Rank
Iron
A universal debugging axiom?
johnr   12/2/2013 4:32:27 PM
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In the software debugging world there's a saying:  "My computer is not the same as your computer."  The idea is the same as in the article:  you need to test under the same conditions as the end user.  In our lab our technical computing people have spend a lot of time and effort to make sure everyone's computer is the "same" so that our DA tools work (or fail!) the same way for every engineer!


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