[sdiy] circuit protection question

[Neil Johnson]

Hi,

Tim Parkhurst wrote:
> The real solution (or at least part of a real solution) would be to
> use a keyed, polarized connector that cannot be plugged in backwards
> or out of position.

MOTM: good
Doepfer: bad (really bad...face-slappingly bad)

There is over-voltage to consider as well.  With the polyfuse approach
it is also quite straightforward to add a crowbar on each rail as well
(resistor, zener, SCR).

But any protection mechanism either needs to be good (adding cost) or
don't bother.  A half-baked protection mechanism is often worse as it
gives a false sense of security.

If you're going to fit polyfuses it might also be a good idea to fit
LEDs as well, so that you can quickly see if the polyfuse has tripped,
or something else is wrong.  Otherwise you could have users doing
"David's" with wire jumpers and then all that protection is for
naught.

Neil
(anyone else sitting in the United lounge at Washington Dulles this evening?)
-- 
http://www.njohnson.co.uk