Thank you for your excellent comments. I agree 100%, and have forwarded this to manager requesting the fusible link.
Bob Butcher -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hamid A. Wasti Sent: Monday, November 07, 2005 5:25 AM To: Protel EDA Discussion List Subject: Re: [PEDA] How do I design a fusible link into a PCB? There are times where products can not afford a 14c fuse but they can afford the consequence of that fuse not being there even less. If there is a product safety issue and someone is hurt as a consequence, can you defend your decision with a less than friendly lawyer grilling you? As much as we all hate product liability lawyers, sometimes their threat makes us think through the consequences of our decisions. Looking strictly from a product liability standpoint, by putting a fusible link, you are acknowledging that you believe that a safety device is needed. Then you go ahead and put in something really inadequate -- you just lost the case. If it can be shown that you put in something that you knew (or ought to have known) to be inadequate just to save money, you are looking at punitive damages. If you do not put a fuse, you can have the position that a safety device was not necessary (provided that that is a reasonable decision based on the big picture of the design). You now have a position where you can at least make a stand, though if someone has already been hurt, you are starting from a bad position. If you really can not afford a real fuse, then design the product without one. A feel good "fusible link on the PCB" that will blow at some unknown current after an unknown time, with the unknowns depending upon the batch of boards and the manufacturing process, does you no good. Regards, Hamid Butcher, Bob wrote: >Thanks for the reference, that is just what I needed. I am pushing for >a real fuse, but may be forced to add a fusible link to the PCB due to >the excessive cost of a 14 cent surface mount fuse! >Bob > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] >On Behalf Of Brad Velander >Sent: Friday, November 04, 2005 10:48 AM >To: Protel EDA Discussion List >Subject: RE: [PEDA] How do I design a fusible link into a PCB? > >Bob, > If you have not already found it, check out WWW.ULTRACAD.COM > > Doug Brooks has studied and written several articles on this subject. >>From my own personal experience many many years ago, the fusible link >is not very reliable. It is only good as an absolute disaster stopping >link that may blow at 3 amps or may not blow until you reach 10 amps >(we were trying to make it a 3 amp link). It may hang in there for 3 >minutes at 8 amps as well. So don't expect any fine tunability, too >many variables and variances for great accuracy. > >Sincerely, >Brad Velander >Senior PCB Designer >Northern Airborne Technology >#14 - 1925 Kirschner Road, >Kelowna, BC, V1Y 4N7. >tel (250) 763-2329 ext. 225 >fax (250) 762-3374 > > > >-----Original Message----- >From: Butcher, Bob [mailto:[EMAIL PROTECTED] >Sent: Friday, November 04, 2005 9:30 AM >To: [email protected] >Subject: [PEDA] How do I design a fusible link into a PCB? > > >I want to add a narrow circuit trace to a PCB design to act as a fuse. >It should operate with 1 Amp of current continuously and open if the >current exceeds a higher value (2-5 Amp). This project is very cost >sensitive and a 15 cent fuse may be too much. I have the guidelines for >conductor heating vs cross section, and it appears the conductor would >need to be less than 10 mils wide on a 1 Oz copper board. Does anyone >have experience with this subject? > >Bob Butcher >[EMAIL PROTECTED] > > >____________________________________________________________ >You are subscribed to the PEDA discussion forum > >To Post messages: >mailto:[email protected] > >Unsubscribe and Other Options: >http://techservinc.com/mailman/listinfo/peda_techservinc.com > >Browse or Search Old Archives (2001-2004): >http://www.mail-archive.com/[email protected] > >Browse or Search Current Archives (2004-Current): >http://www.mail-archive.com/[email protected] > > > > > >____________________________________________________________ >You are subscribed to the PEDA discussion forum > >To Post messages: >mailto:[email protected] > >Unsubscribe and Other Options: >http://techservinc.com/mailman/listinfo/peda_techservinc.com > >Browse or Search Old Archives (2001-2004): >http://www.mail-archive.com/[email protected] > >Browse or Search Current Archives (2004-Current): >http://www.mail-archive.com/[email protected] > > > > > ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected] ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
