Hi Bogdan, I'm sorry if you thought that my previous message was an endorsement for using necked down PCB traces as a fuse. I understand and share the sentiment that it is an unpredictable and probably not even cost effective solution.
I was wondering why anyone would shape a PCB trace in such a way (two triangles pointing at each other with a thin trace between the points). A "fuse" is probably not the likely intention. A reasonable explanation may be a "cut jumper". The triangles make the trace visible; while the thin trace provides an easy spot for the trace to be cut with an exacto knife---- which permanently removes the "jumper". Another reason (suggested by a colleage) are alignment marks used by the PCB fab house to help align layers. Just to be sure... I'm not suggesting the above as design ideas. I'm just trying to figure out why anyone would do such a thing. One solution to the original problem that I haven't seen suggested is the good old "air discharge tube", "gas-discharge tube", "gas tube" ...whatever you want to call them. Of course, they aren't free (about $1 each). They are more predictable than open air terminals, they are UL/CSA recognized and they can handle some massive breakdown currents. They are available from Bourns and Sankosha USA... probably some other manufacturers as well. Chris > -----Original Message----- > From: bogdan matoga [SMTP:bogda...@pacbell.net] > Sent: Wednesday, February 20, 2002 4:19 PM > To: gab...@simex.ca; Chris Maxwell; emc-p...@mahordomo.ieee.org > Subject: Use of PCB Traces as Fuse and Voltage suppressor > > Gabi: > I believe that there is a basic rule which is not published anywhere: > when you design something, then do it right. > When transient suppressors are needed, then use the correct component, > which will not depend on Paschen's Law and give predictable > performance. > > Same for "necked down" fuses. > When you want performance, then do it right. The above original > suggestions are perfect for Mickey-Mouse-engineering. > Bogdan. > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
