The devil is in the details, as the saying goes, and nowhere more so than in circuit protection. A tiny oversight in circuit protection can make the difference between a great product and a dangerous one, and yet, some device designers still aren’t giving the field as much consideration as it needs, according to LittelFuse’s senior application engineer Bob Capdevielle.
Capdevielle’s day to day job consists of being on the front lines of circuit safety, answering scores of queries on a daily basis from engineers about product design, and where fuses fit in.
Via email, phone and sometimes in-person meetings, Capdevielle attempts to help them all, letting them know what works, what doesn’t and how something can be adapted to accommodate.
Lack of good circuit protection can, of course, result in some less than desirable outcomes, including electric shocks and fires. These in turn can be fatal, so it’s certainly no trivial matter, and Capdevielle takes his job very seriously.
A sudden surge of electricity, say from a lightning bolt, could be catastrophic for devices without the right circuit protection, he told EE Times, which is even more risky now that “more and more energy is being put into smaller and smaller packages.”
Even famous examples like the Hubble space telescope have paid the price for poor circuit protection design. “We have about 900 fuses on that thing and some were picked wrong,” said Capdevielle, though he noted the NASA engineers involved were not amateurs in any way, shape or form. “These are not just people straight out of college, these are pretty sophisticated guys. But as the item itself gets more and more complex, it gets easier and easier to make mistakes,” he explained. Fortunately, in that particular incident, Capdevielle was able to help and they were able to make the necessary changes to get things back up and running again.
As well as NASA, Littelfuse also deals with circuit protection queries from the military, though Capdevielle said he couldn’t talk much about that for confidentiality reasons.
The military, he said, sometimes had difficult requests, that pushed the boundaries of circuit protection design, but as he explained it, “we’re stuck with the physics of what the parts are and what they do.”
Capdevielle said he wished more designers would brush up on their knowledge of fuses and the concepts of “I squared T” – the amount of energy it takes to melt a fuse. “There’s a constant misunderstanding of what that means” he said.
In the meanwhile, however, Capdevielle is there day in and day out, fighting fires and providing engineers with the help they need.
The products used in special areas like petrol chemical industries,pharmaceutical industries or at any safe areas are designed and tested with many standards. These product designs not only focuses on fuses but the spacing classes which defines the separation distances of tracks,components,wires and many more to avoid even a smallest amount of spark or arc.
Nice article Sylvie - in these days of billion-transistor ICs the humble fuse gets oft forgotten. Littelfuse have some good resources on their site, particlarly the "Fuseology" primer:
And BTW Sylvie that video worked fine in IE8.