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William K.
User Rank
Platinum
Large manufacturers
William K.   8/15/2011 10:19:49 PM
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Interestingly enough, the way that I add information to the drawings was a cost-reduction thing, since debug time is expensive, much more than build time. So to make our planned profit we had to get things right every time. Adequate information helped a lot. 

But really, if the individual doing the PCB layout does not understand what the circuit does, you can have some very interesting problems with board layouts.

TJ McDermott
User Rank
Blogger
Re: Common sense on PLC I/O
TJ McDermott   8/15/2011 9:58:24 PM
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William K, I agree with EVERYTHING you say.  The effort you put forth makes for a good design.  The effort put forth by the manufacturer in question was NOT sufficient to make a good design.  When the schematic is not immediately available, a well designed component assists in fast troubleshooting or assembly.  The product line in question does NOT.

William K.
User Rank
Platinum
Common sense on PLC I/O
William K.   8/15/2011 8:59:21 PM
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I agree that the different connection schemes shown are not all intuitive. That is the case with a few makers of PLCs. The result is that when I create a controls drawing that includes a module, I put a "map" of the module right there on the drawing. Smetimes it just shows the terminal screws in the actual relationship, sometimes it includes more details. They always include the module nme, function, and number. In addition the address of each connection may be shown.

As to why they are arranged so strange, it probably has a lot to do with the internal circuit board and what components are installed on it. I have done PCB designs and sometimes getting the connections in the most desireable places is quite an effort. Also consider that the circuit board designer may not have a fraction of a clue about the circuit functionality. I have had that kind working for me also.

failureindesign
User Rank
Gold
symptomatic
failureindesign   8/12/2011 4:09:24 PM
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The problem is lack of experienced oversight, just like the recent BMW driver settings issue. One cannot expect to just go coding without proper guidance (from management and specification) and expect not to have a mess.

The issues described herein are especially grievous because those making the big bucks, if you will, are being paid those big bucks to know better ... and yet they don't. Hmmm ... maybe paying the big bucks really does NOT ensure quality of work. Oh what an epiphany!

If one is going to "spread out the work", one MUST FIRST establish the proper documentation and specificiation of the work to be done in comprehensive clear and certain terms. It is just insanity to do otherwise and, frankly, actionable IMHO as misuse and abuse of company resources. Not to mention that if someone is killed because of the resulting confusion in use, just because the OEM likely won't be sued makes it no less culpable. Life is dangerous enough without someone designing more in.

TJ McDermott
User Rank
Blogger
Re: Who owns the design/platform?
TJ McDermott   8/12/2011 12:24:12 PM
NO RATINGS
You're right jmiller; the project manager for the product should have caught this.  I wonder if it was caught, just too late because molds were already fabricated.

TJ McDermott
User Rank
Blogger
Re: Figure 4
TJ McDermott   8/12/2011 12:23:05 PM
NO RATINGS
Dave, thanks for responding in the spirit of the post!  However, I think in light of new evidence, I must ask for a recess.  I may have discovered new evidence of an even more egregious crime.  The evidence submitted so far shows simple bad engineering.  The new evidence, hopefully displayed next week, I hope you will find as proof of sabotage by the large manufacturer.

jmiller
User Rank
Platinum
Who owns the design/platform?
jmiller   8/12/2011 12:10:14 PM
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Often situations like this arise when there is no ownership of the platform or designs within the platform.  I've heard stories of one group trying to reduce cost by changin materials while another group is making tooling changes in improve performance.  Talk about trying to hit a moving target.  Let's change to a material with a slightly different shrink rate while we are changing the tool.  How can the supplier have any chance of success of meeting the tolerances on the print.

Mr. Right hand, meet Mr. Left Hand.  Why don't you two take some time to get acquainted.

If there is one central ownership of the entire system/platform/design then all changes, new products, have to go through one group in order for alignment.  Great concept, but it can slow things down and cost a little more.

Dave Palmer
User Rank
Platinum
Figure 4
Dave Palmer   8/12/2011 12:09:17 PM
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This isn't just a lack of common sense; it verges on a sadistic desire to inflict mental anguish on anyone who has the misfortune to have to use this unit.  Given the extreme maliciousness of this crime, I recommend the maximum penalty. 

Charles Murray
User Rank
Blogger
Re: Scary stuff
Charles Murray   8/12/2011 11:12:44 AM
NO RATINGS
Agreed, Beth. The worst part of this is that it's so common. How many times have we all seen products get worse during the course of their evolution? New ideas don't necessarily make for better products.

Beth Stackpole
User Rank
Blogger
Scary stuff
Beth Stackpole   8/12/2011 8:21:12 AM
NO RATINGS
Forget about the lack of common sense, this points up a much larger issue that many companies are still stuck with siloed design processes where one functional group or division doesn't have any idea or ability to tap into work that's being done in another part of the company.

If this is their best excuse: "The best answer I could get from a representative of this manufacturer was "The electronics module [the device with the LEDs] was made by one branch of the company, while the base and terminal block were made by a different branch."--that's pretty darn scary!



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