While out shopping for the usual
electronic stuff that I like so much
I discovered this Hyundai
four way extension socket
with surge protection
and since I already took one apart recently
I thought it'd be interesting to see another version
and this is a second take of the video
because I really fluffed the first video up
but
on the plus note you actually get to
not see me hunting around for the correct screwdriver for it
which for this it's triangular screw heads
and also
it saves you having to watch them all get taken out
and me then cutting the electronic module out
so here's the surge protection module
and if you recall the last one just had
three metal-oxide varistors
as does this one
and I was saying normally they'd have
thermal fuses just for extra protection
when these start to fail
this one has thermal fuses
now one notable feature in here
I'm not sure it should be called a feature as such
is that when this was in here there was
a little bit of heatshrink around it
and the neutral had actually been nipped
and the screw was driven right through the actual wire here
but the neutral's not the hazardous one
it's theoretically normally at ground potential anyway
and the screw is recessed so it's not a big thing
but it is a bit sloppy in the manufacturing
another notable thing is that the module here
also has the little lead going out
to a neon with a little inline resistor here
and it's a green neon, it's one of the little
NE-2 lamps with the green phosphor inside
quite nice
and if we look at the schematic for this
let's see if I can make sure this is lined up here
yeah that looks pretty good
if we look at the schematic you can see
there are the three metal-oxide varistors
and they're between live, neutral and earth
however, on each of the live and neutral
we have the two thermal fuses sandwiched
between the metal-oxide varistors
the metal-oxide varistors are smaller than the ones
in the last unit which means they've got a lower ability to
absorb, you know, a significant number
of surges
this would probably last less
time than the other one that didn't
have the thermal protection
but this one is less likely to set your house on fire afterwards
but the nature of these metal-oxide varistors
is that every time they absorb a transient,
every time their voltage is exceeded
then, they, I'm going to slip the cable
from this microphone it's just wangled its way off
my shoulder here
every time they clip a transient, their voltage
is exceeded, they just end up just failing
a little bit internally, they just gradually
break down over time
and that results ultimately, when they've
really failed and the heat and in that case these
these electronic, these thermal fuses will blow
and these are the thermal fuses here
I wasn't sure what the actual symbol for a thermal fuse is
so I just drew a fuse and wrote a degrees centigrade next to it
and another notable feature here is that the
neon is actually after the thermal fuses
so theoretically when one of the thermal fuses trips
then the green neon goes out to indicate there's
no longer any surge protection
however that's slightly defeated theoretically if there
is any leakage through this
and this thermal fuse went you'd end up
losing the live to neutral protection
but theoretically the live could find a path
through the neon and if this was leaking slightly
a route to earth so it's not an infallible approach
having the neon light that but it should ultimately
work, I guess
The metal-oxide varistors involved are
H E L 10 D 4 7 1 K
where the 4 7 1 usually indicates
4 7 and one 0, 470 Volts which is the sort of rough
mean voltage before they'll actually start conducting
and if you consider that this designed for 240 volt use
in the UK
and our peak mains voltage is sort of about
330 volts it's got a modest margin before
it'll actually kick in to start clipping transients
so really it's, to me a better design than the other one
now I'm wondering what was in the others that were on the same shelf
that was the only one branded Hyundai
and the other ones all had those horrible little
press rivets that have been put into the plastic
that make it very hard to open the cases
and that was the only one held together by screws
so I'm wondering what was in the other ones
certainly this one, it looks pretty typical
this is ultimately what you find in a fairly good, modern
transient suppressor. It's not a terribly expensive device
to add to a socket
certainly not as much as, you see some of these
surge protectors with ridiculous prices for
what is probably just this inside
it's a perfectly functional little unit
it's got that thermal protection that I like
and it's got the little neon that will at least
give an indication if the protection has tripped
due to a lot of transients or maybe a lightning strike or something
but yeah it looks a pretty typical and pretty good unit