At 12:34 PM 6/15/01 +1000, van de Werken, Matthew (DEM, PH) wrote:
>I can't think of a single good use of using a track as a fuse - if the
>"fuse" blows, you basically have to toss the board. Surely it would be
>(marginally) better to use a low-ohm resistor as a fuse?? Of course, the
>ideal situation is to use a fuse as a fuse, but as we all know we don't
>always live in the ideal world...
Okay, here's a situation. Since it is hypothetical, it need merely be
possible and not at all normal.
(1) High production run of
(2) cheap pcb
(3) connected to another device which is more expensive and which could be
damaged if high current continues for a long time.
(4) the pcb assembly can easily be replaced by the user if it fails
(5) normal operating current is far below fuse current so the gross
variation in fuse current is tolerable.
(6) short conditions will be rare
(7) there is no fire hazard from fusing or sub-fuse heating of the pcb with
the copper fuse on it.
(8) if the fuse fails to open the circuit, there would be no hazard to life
or very expensive damage.
(9) a real fuse would be too expensive. Or there isn't room for one.
Under these conditions *maybe* one would use a fine copper trace as a fuse.
Otherwise just buy a fuse and solder it in. It will be much more reliable
and not much more expensive.
[EMAIL PROTECTED]
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433
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