John Larkin wrote:
> On Thu, 19 May 2022 19:12:20 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> John Larkin wrote:
>>> On Thu, 19 May 2022 17:10:04 -0400, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> Martin Brown wrote:
>>>>> On 19/05/2022 16:14, Jeroen Belleman wrote:
>>>>>> On 2022-05-19 17:03, jlarkin@highlandsniptechnology.com wrote:
>>>>>>> On Thu, 19 May 2022 07:40:45 -0700 (PDT), Lasse Langwadt Christensen
>>>>>>> <langwadt@fonz.dk> wrote:
>>>>>>>
>>>>>>>> torsdag den 19. maj 2022 kl. 16.36.23 UTC+2 skrev
>>>>>>>> jla...@highlandsniptechnology.com:
>>>>>>>>> On Thu, 19 May 2022 12:58:33 -0000 (UTC), Keegan Major
>>>>>>>>> <keegan...@hotmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Clive Arthur <cl...@nowaytoday.co.uk> wrote:
>>>>>>>>>>> On 19/05/2022 04:27, Sylvia Else wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Is your channel really that noisy that you cannot just discard bad
>>>>>>>>>>>> packets?
>>>>>>>>>>>
>>>>>>>>>>> I don't have control over the transmission path, it may be noisy, it
>>>>>>>>>>> may not - it's not a fixed installation. [snip...] I can't request a
>>>>>>>>>>> resend, and sending multiple copies restricts bandwidth too much.
>>>>>>>>>>
>>>>>>>>>> Hmm, 17 messages in to the thread, and the group finally is told some
>>>>>>>>>> of the critical unstated requirements that *should* have been part of
>>>>>>>>>> the initial message, and would have avoided about 14 "can't you
>>>>>>>>>> resend"
>>>>>>>>>> or "can't you send multiple" messages.
>>>>>>>>>>
>>>>>>>>>> Don't you think this above should have been in your initial post so
>>>>>>>>>> that the rest of us, who can't read your mind to divine unstated
>>>>>>>>>> limitations, were appraised of some rather critical limitations?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> It's normal here to get underspecified problems. Details usually
>>>>>>>>> emerge, but some people do refuse to explain their top-secret
>>>>>>>>> projects.
>>>>>>>>
>>>>>>>> https://xyproblem.info/
>>>>>>>
>>>>>>> Underspecified problems do encourage lots of lateral/goofy thinking.
>>>>>
>>>>> Almost all of which is completely wasted. Your proposal of send it three
>>>>> times and vote best out of three being amongst them.
>>>>>
>>>>> There is just about enough space to do what the OP wants but whether or
>>>>> not they have the mathematical sophistication and programming skills to
>>>>> implement it quickly enough to be useful is still an open question.
>>>>>
>>>>>>> Of course, some people are hostile to ideas. Their career path is more
>>>>>>> McDonalds than electronic design.
>>>>>
>>>>> You have that *EXACTLY* backwards.
>>>>>
>>>>> If you cannot adequately describe the exact problem that you are trying
>>>>> to solve then you will spend vast amounts of effort solving the wrong
>>>>> problem(s) again and again. I have seen it happen many times.
>>>>>
>>>>>> Goofy ideas aren't really welcome if they upset a sizable fraction
>>>>>> of effort already invested. Ideas are cheap. Realizing them is costly.
>>>>>> You'll want to be selective.
>>>>>
>>>>> +1
>>>>>
>>>>> Half the battle is specifying the problem and any hard constraints so
>>>>> that proposed solutions will actually stand a chance of working on the
>>>>> available hardware and quickly enough to be useful.
>>>>>
>>>>
>>>> I'm way more in JL's camp, although not 100%. (I do more math than he
>>>> does.)
>>>
>>> Yes, I work more by instinct and simulation. But my world is largely
>>> nonlinear, where the math is basically impossible.
>>>
>>>>
>>>> Of course you don't want to take the first thing that comes into your
>>>> head and build that--nobody's advocating that here AFAICT. I've seen it
>>>> a lot in the wild, though. In fact, one outfit I had to deal with (a CE
>>>> in Orange County CA) kept ignoring advice that was backed up with
>>>> detailed mathematical analysis and a _working_prototype_ of what they
>>>> were supposed to build. (That transcutaneous blood glucose thing again.)
>>>>
>>>> They just trying things randomly until they ran through the client's
>>>> money and then quit. One time when I pinged them about it, a bright lad
>>>> smiled and said, "That's engineering!"
>>>>
>>>> Riiighhhtt.
>>>>
>>>> But a lot, a lot of people seem to have very little emotional tolerance
>>>> for being in a state of uncertainty. I can't prove that, but over and
>>>> over I've seen folks spend far too little time turning the problem over
>>>> in their minds, talking at the white board, and so on, and just charging
>>>> in and doing the first thing that seemed plausible.
>>>
>>> Yes. Uncertainty makes many people uncomfortable, so they lock down an
>>> architecture as soon as they can. I've seen horrors.
>>>
>>>>
>>>> That's super dumb. At the beginning of the process, you have to
>>>> cultivate offbeat ideas, because (at least in the sort of gizmos I
>>>> build) there's usually some way to do the task much better and/or
>>>> cheaper than what's out there.
>>>>
>>>> In general you should spend something like 10% of the time figuring out
>>>> what you should build, and the rest designing and building it. Skimping
>>>> on the one very often leads to poor results on the other.
>>>
>>> Brainstorming and a period of confusion can often greatly simplify the
>>> design, or add nifty features. It's well worth the tradeoff.
>>>
>>> Design is a partly emotional process, which lots of engineers don't
>>> want to admit either.
>>>
>>
>> One time long ago, I was in a two-day class for OS/2 Presentation
>> Manager programming. (I did say it was long ago.) ;)
>>
>> At one point, the presenter (who was actually very good) asked us two
>> questions: Is design an art or a science? What about debugging?
>>
>> Just about everyone said that design was a science and debugging was an
>> art. That's backwards.
>>
>> A design is done when the designer says it's done, generally including a
>> good long list of checks for performance, DRC, EMI, ROHS, MIL HDBK 217,
>> ad nauseam. There are nearly always a ridiculously large number of
>> different ways to do the job, if you count all the combinations. That
>> makes it an art.
>>
>> On the other hand, troubleshooting is definitely a science. There's a
>> problem someplace, because this item doesn't behave like the N previous
>> ones that worked. You find it by applying critical tests and reasoning
>> about them, and when the problem is found and fixed, everyone can agree
>> that it's gone.
>>
>> Debugging first articles is a bit of both, because you often find design
>> screwups (hopefully minor). In my world that often includes
>> layout-dependent stuff such as how high a current can you run through
>> your 12 GHz pHEMT or 45-GHz SiGe BJT before it becomes unstable.
>> Swapping out jumpers for beads, tweaking current sources, that sort of
>> stuff.
>>
>> In rare instances it's something really stupid such as upside-down power
>> supplies on an op amp, but normally the first articles are shippable
>> with maybe a roach wire or two.
>
> After some years, we have evolved procedures that mostly prevent
> getting V+ and V- swapped on opamps.
>
>>
>> We have had the occasional disaster, such as a small module with three
>> SMPSes on it to make several rails from a +24V wall wart. The negative
>> rails were made by an AOZ1282 async buck running off the output of an
>> LMR23630 sync buck (+13 -> -12 and +24 ->+13, respectively).
>>
>> The A-O part is generally super well behaved, but the two together
>> produced a _ridiculous_ selection of high harmonics of the LMR23630's
>> 2.15 MHz switching frequency. It was the stuff of nightmares--measuring
>> one node produced a big peak at 182 MHz, and another one nearby had
>> another peak at 121 MHz, selected by various incidental resonances.
>>
>> With that one, we just cut our losses. ;(
>>

> We recently had an LTM8078 "Silent Switcher" screaming at us in 400
> MHz bursts at 2.5 MHz. The embarassing part was that the customer
> discovered it. Oops.
>
> A nice ancient National 50 KHz Simple Switcher fixed that, with a
> board spin of course. And gigantic inductors.
>
> https://www.dropbox.com/s/ah90qsi0007ymjv/Mon_Noise_2.jpg?raw=1
>
> https://www.dropbox.com/s/9grk3iqwzifmw6w/Mon_Noise_LTM8078.jpg?raw=1
>
I've had good luck with the 150 kHz ones too, with Schottky catch diodes
to prevent current spikes from PN diode recovery. They do tend to need
chunky inductors to handle all those voltseconds.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com