Joel, You don't really give any information on what type of machinery you are looking at this emergency stop switch for, so it is hard to describe exactly when it is mandatory. It probably depends on what the equipment is, what risks it represents to those who use it (or are in its immediate vicinity), and what standards & laws you will be held to. What country & industry are you designing this machinery for use in? A small town lumbermill in the United States will probably have a whole different set of rules & regulations than a multi-billion dollar semi-conductor fab plant in Ireland. Your question about whether an emergency shutoff switch should just stop the machine, or cut all power, is also a difficult one to answer without know what type of machinery you are talking about. Philosophically, I would think that hitting an emergency shutoff switch should NOT create ! more hazards, but that means it's up to you to decipher how the machine is built and whether cutting all power during operation may cause a risk to users because a cutting edge stays exposed or a particular gas continues to vent or whatever. Regarding how long the machine can run or function after the switch is pressed, or how long the emergency stop button must be pressed before the machine shuts off - I have absolutely no idea. Again, it depends on a lot of things that you haven't put in your e-mail, including how much risk there is to users (does the machine give the operator a nasty scrape on their arm if it malfunctions, or does it kill every living thing within 50 feet in 15 seconds). Finally, regarding whether the emergency shutoff switch must be hardware, or can it be software - it might be dependent on what the machine is and what industry it is used in and what country it is used in, but in general I wo! uld be REALLY concerned about trying to implement an emergency shutoff switch with software. With software, you need to make sure there are no potential software bugs, including anything in the programming at all that could lock up the processor, there are no EMC vulnerabilities, there are no concerns about ESD on the switch frying the electronics or processor, etc. etc. But a hardware switch is a switch, not much more. Hardware switches typically don't suffer from firmware problems, compiler bugs, etc. -Camille Portland, Oregon
Joel Sandberg <[email protected]> wrote: To List Members; I would appreciate guidance on the subject of emergency stop switches (buttons). When (if every) is an emegency stop switch manditory? Must an em! egency stop switch be a hardware only function, or can it operate through the machine's computer and software? Does the emergency stop switch have to turn off power to the machine, or can it just stop the offending action, while leaving power on? What sort of responce time should be expected for an emergency stop switch (2 part question): a) How long (realy how short a time) must the operator hold emergency stop switch in order for it to operate (i.e when I want to hit the button and run, how long to I need to stand there and hold the button before it functins)? b) How long can the machine continue to move/run/function after the switch is pressed? Thank you. J. Sandberg __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com - --------------- ------------------------------------------------ This message is from the IEEE Prod! uct Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
