specs that end up butchered by reality? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: September 15, 2019, 10:29:28 pm
content: What are some examples of specs that are butchered by reality?I noticed that with heat sinks.. optimal ones are pretty damn weak to impact (like on chassis exterior). (500 simulations later you realize its like a dandelion)Did you ever spend a long time trying to max some kind of equation out then you found the implementation is ridiclous, fragile, etc? and then that the solution is basically a difficult to explain hack job? (why did this take so much time??)

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 15, 2019, 10:46:24 pm
content: It's better than reality ending up butchered by specs...

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 15, 2019, 10:50:31 pm
content: Quote from: SiliconWizard on September 15, 2019, 10:46:24 pmWho says it isn't?

author: coppercone2
author_rank: Super Contributor
timestamp: September 15, 2019, 10:58:58 pm
content: god

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 16, 2019, 12:19:36 am
content: Not sure who that is.Anyway, I guess examples of specs that are butchered by reality: many Li-ion batteries of dubious origin.An example of reality butchered by specs? Maybe the Boeing 737 MAX's MCAS?

author: coppercone2
author_rank: Super Contributor
timestamp: September 16, 2019, 12:45:16 am
content: no no, I meant something along the lines of where you do alot of optimizations to your design and it turns out for some weird reason its all useless and that thing you thought of when the project first began as being too simple is the correct answer (after you found some design options)not necessarily negligent or complicated, just odd

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 16, 2019, 01:42:38 am
content: Quote from: coppercone2 on September 15, 2019, 10:29:28 pmIt is a poor craftsman that blames his tools.Or a good anecdote from the great Richard P. Feynman: he was with some colleagues discussing computer science research. The subject was a learning and optimizing system, which was programmed to find any way necessary to achieve its end goal. Well, the first thing it found was to simply set the end goal memory address to the goal value. Okay, well, that's not helpful. So they added conditionals prohibiting direct "hacks" like that. While the CS guys found it a bit annoying, Feynman found it amusing; they literally told it to find any solution, and it dutifully did!To explain better:So you're optimizing a problem with respect to a certain number of variables, but disappointed when the solution apparently unexpectedly ends up suboptimal in other,previously undefinedvariables? So you really weren't solving the problem you thought you were; you should've specified itproperlyin the first place!Writing a comprehensive spec, of course, is half the challenge of engineering. Failing to do so, is not much different from any other bug or omission in ones' work, just part of the job.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: September 16, 2019, 06:14:20 am
content: not tools, im not saying its not manufacturer-able, just later you look at it and some other detail comes to mind and you are laughing because the 'looks right' solution was the best one after all\the idea that its something random that comes up. which makes it funny.

author: Berni
author_rank: Super Contributor
timestamp: September 16, 2019, 06:53:09 am
content: I like to call that "over-optimizing"In quite a lot of cases when you really really optimize a design for one specific spec you will be in trouble. What you end up with tends to be one of more of the flowing:1) Ridiculously unpractical to build: Oh so maybe using 100 opamps in parallel might be a bit expensive... but the noise is nice.2) Needing a very strict use case to work: Look it works great... tho if my warm breath touches it the output drifts off towards the supply rail faster than you can say oh cap.3) Sucks at other specs: Look my amplifier can output 2kW with that tiny heatsink... but the THD-N is 60%Its not that these "over optimized" designs are bad designs. But by the time you reach them the applications for the design become so niche that you might not be able to justify it. But a good design is a design that hits ALL of the relevant specs simultaneously (Even if the said specs might not be so impressive on there own). That's what engineering is about.

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 16, 2019, 02:59:28 pm
content: Yeah, you can call that "over-engineering" as well.But if your over-engineering eventually fails to survive reality, then as T3sl4co1l said, it was probably ill-specified and/or unproperly modeled.If it doesn't fail, but could be done with a simpler solution - well it's exactly what engineering is all about. Finding the simplest solution, but not simpler than that, is the holy graal of engineering. Some have spent a lifetime finding the sweet spot.

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 16, 2019, 04:25:47 pm
content: Quote from: coppercone2 on September 15, 2019, 10:58:58 pmI never said such a thing.

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 16, 2019, 04:27:59 pm
content: Quote from: coppercone2 on September 16, 2019, 06:14:20 amConsidering how many posts you've made about the actual intent of this thread I'd say it's one example.

author: dom0
author_rank: Super Contributor
timestamp: September 20, 2019, 12:06:43 am
content: QuoteLots of power MOSFETs.