Vote on Article?

[Chris Elston]

Should we keep this article? http://www.mrplc.com/kb/index.php?page=ind...;id=77&c=38 I always like to give people a chance.

[panic mode]

i have nothing against this article or articles in general. in fact i read them all with great interest. it takes energy to produce something and this is excellent way of learning. but since this is engineering forum, any article, post or submission should be open for debate or discussion. after all there will always be more ideas, improvement suggestions or questions to be answered. this is what forum is all about and engineering forum is no different. this article seam to be the only post of the autor, couldn't even send him an email. maybe posting articles should be limited to forum members (another thing to discuss). what bugged me was not the fact that author didn't return to look for any comments replies or that in his own words, he was away from this field for years, wasn't aware of safety categories until recently etc. this is normal and happens to many people. i don't mind if person with little or next to no exposure to subject decides to write an article or first experience. this is forum and everyone is entitled to opinion. it is good to see path others take when facing a challenge or something new. but this is sensitive subject, it deals with safety and deserves a bit more attention. this idea of safety circuit looked interesting but it wasn't new at all. i've seen same thing proposed about 20 years ago by one of my teachers. nothing wrong with saving 350 out of 400 dollars but this is too good to be true... it paints wrong picture on delicate subject where industry (and regulations) have been working for years. proper safety circuit design starts with analysis of the hazard and ends with selection of circuit of specific performance suitable for the application. performance of safety circuit is not measured in dollars saved on skipping safety relays. it is measured in number of correctly applied series of measures that cover specific types of failures. the only failure analisys in this article is focused on relays, there is no mention of failure or damage to wiring, ground faults, short to power, cross channel faults etc. and this makes it flawed concept. this approach could be acceptable for certain cases as defined in categories but again, there was no mention in article of requirements of each category or what category level is met with mentioned design. incorrectly applied Cat4 controller will not produce Cat4 safety circuit, it could be only Cat3 or 2, or even one (and I was involved in project with big company who had done just that on a product made in mass quantities - use Cat4 controller as Cat1 circuit on a very dangerous piece of equipment - servo press!) this thing can kill people you know, and I'm sure Mr. Anderson doesn't want his name mentioned in case of such investigation. who can blame bubba for using circuit from article posted on engineering forum and signed by someone with BSEE degree...? ... just my $0.02...

[entertron]

What's the reason for asking?

[JesperMP]

I can understand what you mean. It has been mentioned many places that forum providers can be held responsible for the contents of posts, that is if the forum provider has knowledge about questionable content. A technical forum like this one was probably not in the minds of the lawmakers when the law was aggreed upon. However, in principle of the law you can be held responsible. And morally, if you believe a post is wrong about safety principles, then you should be just as obliged to take action, if nothing else than to preserve your own peace of mind. So I say, "delete the post". And then announce that you have done it, and why you found it necessary to do so.

[Chris Elston]

It's been removed.