Electronics Forum / Electronics / September 2008

"David L. Jones"

** I believe it is totally illegal to use a 240 volt plug or socket for any
other purpose than as a mains connector.

Back when I was a keen model power boat racer, one of the club members
showed up at the lakeside with a new 12V starter motor fitted with a
standard 3 pin mains plug.  He had also fitted a double power point to his
tool box to allow connection to the 12 volt battery he kept inside. The
other socket allowed him to plug in a 12V fuel pump.

Thing is, the guy made his living as an electrician  !!!

Besides being ludicrously  DANGEROUS  the idea will not work reliably as the
brass plug pins and female socket parts are very prone to tarnishing and
when thick enough this tarnish will fully insulate at 12 volts.

One of the reasons why the earth pin has to be nickel plated nowadays.

.....   Phil

An old friend did something like that for his radio gear, only he used
DC sockets to supply 240VAC. <shrug>

He blew up at least one radio that I know of.

- Franc Zabkar

I remember an Iranian friend telling me that for a while Iran used the
same wall sockets for AC mains as for telephones. People would
sometimes plug a telephone into the mains. The phone would ring,
presumably at the mains frequency, and then die.

This Wikipedia article shows one plug style as CEE 7/17 Euro 2 pin:
http://en.wikipedia.org/wiki/List_of_countries_with_mains_power_plugs,_voltages_
and_frequencies

This article shows that the CEE 7/16 2-pin plug was used in older
installations:
http://en.wikipedia.org/wiki/Telephone_plug

- Franc Zabkar

Yes, got quite a shock seeing that,  however in times gone by I have
seen mains fittings used for car to trailer connectors, as connectors
for "slot car" hand controllers (for public use) in an amusement
centre, and even as speaker connectors when I was in school (cant
remember if it was the 240 type or the 2 pin US type). Fortunately now
there are many more "correct" low voltage plugs and sockets available
to the hobbyist via Auto suppliers, dick smith and similar stores,
this probably wasn't the case prior to the 1970s, and people would use
what was commonly available - household fittings.

I can only assume that SC did this in order to provide an example of
HOW NOT to do something.

If he ABSOLUTELY HAD TO use this system, he should have at least used
the neutral and earth as the + and - connectors, and sawn off the
active pin.  At least then, there would be much less risk of danger if
it was plugged into a 240v socket mistakenly.

The other problem with his system is that Mains fittings are clearly
labelled "AC ONLY" and are probably not designed to be used with 10A
DC, especially if there are switches involved.  You are also limited
to 10amps (via the CB in the power board he used) which kind of
defeats the purpose a bit if you want to connect higher current
equipment.

SC should have pointed out that for low voltage use, (32v lighting
plants?) there is a plug and socket available - similar to the 240v
unit, but with the pins arranged in a " T " configuration.  Dick smith
had these, and no doubt Haymans etc would be able to get them for
you.

Alternately, go to Super Cheap or Autobarn, and check out the
connectors etc that they use for the high wattage sound system
installs. These would be far superior in current handling to any mains
plugs.

Also this Reminded me of another article in either EA or ETI some 25
years back showing where some fool had decided to convert his Telecom
phone system to a mains plug and socket arrangement so he could carry
the phone around his house and plug it in anywhere he wanted.  (at
that time it probably was near impossible to buy the proper "Telecom"
type sockets for the average hobbyist?)