Ken said:
Hi,
I have ben looking for a web site that would show me how to secure a circuit
from spikes , over load or anything that can possibly go wrong in a
circuit. either power from batteries or from an outlet.
Ex: putting a fuse at the input of the primary side of a transformer in
series with an on/off switch.
Ken
Hi, Ken. The circuit you're looking for doesn't exist. Too many
things can go wrong, and many times adding on blivets and other
creations creates its own problems which also lower reliability, like
MOVs or transzorbs.
If I'm making an electronic project where I want high power supply
reliability, and I can afford the heat and weight, I'll just purchase
and build in a linear open frame power supply with overvoltage
protection from a good manufacturer. Nearly all of them are based on
the venerable LM723, which can easily be scaled up to amps of current
with pass transistors. They always provide very well regulated power,
and are pretty much impervious to line transients and spikes. Since
they provide current-limited power, they're also well-protected against
most things that can happen to the circuit being powered, too. If you
use these power supplies conservatively (<50% of rated maximum load),
they're pretty much indestructable. Eventually the filter caps will
dry out, but that's at least years and quite possibly more than a
decade down the line.
Not only that, but if they fail or you schedule replacement, they can
just be unbolted and replaced as a unit fairly easily. And they're
still fairly commonly available as surplus for the hobbyist. That's
certainly a much better choice than anything you could make for the
equivalent cost.
Of course you need a fused line voltage input, and the switch is just
common sense.
Good luck
Chris
