Fred said:
I'm putting together a circuit board to take in 12V at less than 1/2 amp
from a wall wart. The unit will have a power jack to suit.
In this design a fuse will be very large or non-resettable or expensive. I
already have a diode so reverse polarity won't be a problem but what exactly
are the rules regarding fuses? Do I need one?
I'm in the UK.
I called the psychic hotline to fill in the gaps.
They said that the actual safety of the device is independent of
location. The ONLY reason it might matter that you're in the UK
is that you need third party agency approvals for the device.
The cost of a fuse is inconsequential unless you're in high volume
commercial production of a very low priced item.
While it's fun to let people vote on the internet, the only vote that
counts is that of the safety test engineer that will approve your
product. Read the regulations and/or call the testing agency. You'll
save yourself a LOT of grief.
And if you expect to sell one outside the UK, you might wanna be reading
many other safety standards. You might find that the presence or
absence of the fuse is the least of your problems. Back in the day,
standards for different countries required mutually exclusive wire
colors. This is probably fixed by now.
Wall Warts dramatically reduce, but do not eliminate your need to
understand the safety rules.
Don't get me started on product liability laws. Say you specify a wart
and it all passes the test. Next year, some bean counter substitutes a
different wart. Same specs and certifications on the wart, but it's 8
cents cheaper. Nobody else even knows it happened, much less tested it.
Creates new fire hazard...somebody's gonna get sued...
Or maybe someone substitutes a car battery for the wart.
If the cord ain't permanently attached, you're at risk.
So, even if your safety test engineer says you don't need a fuse, your
attorney might disagree.
Are we having fun yet?
mike
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