Hi Kiste,

Thanks for the figures. I hope not to forget them :)

I had a look at last Arduino design (Uno). They use a 500mA polyfuse,
resettable, claiming it'll add a proctection layer, in addition to the one
included in USB host. From Jaluino Medium discussion, I understood polyfuse
doesn't act fast enough, that's why it uses a "standard" one. This would
make two reasons Arduino wouldn't be suitable to USB regarding fuse
protection. Unfortunately, polyfuses remain the most interesting option:
easy to find, small, reusable...

Cheers,
Seb

2011/2/6 Oliver Seitz <[email protected]>

> >So I'd need 300mA to protect 500mA ?... Or I could 500mA knowing it'll
> blow at 800mA
>
> It takes it's time to blow a fuse. For a super fast acting SMD fuse I
> already gave some numbers, here a bit more detail, example is a 500mA fuse:
>
> It will *not* blow within 1 hour at 625mA,
> it will blow in less than 5 sec. at 1000mA,
> it will blow in less than 1 msec. at 5A.
>
> Some numbers for a time-lag fuse:
>
> It will *not* blow within 4 hours at 500mA,
> it will blow in less than 5 sec. at 1000mA,
> at 5 A it will blow in less than 100ms, but not before 10ms.
>
> So, if you put those two in series, only the super fast fuse will blow at
> very high currents, while at modest overload any of the two can blow. If you
> want to protect a 500mA fuse in your computer, you would have to use an
> external fuse rated not higher than 300mA.
>
> There are books about connecting fuses in series :-)
>
> Greets,
> Kiste
>
>
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-- 
Sébastien Lelong
http://www.sirloon.net
http://sirbot.org

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