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AUSTRALIAN DESIGN
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phenomena such as microseismic noise which has a scale
size of several tens of kilometres.
Michael Andre Phillips,
Coonabarabran, NSW.
Proposal for lower supply voltages in the home
Here is my perspective on the April 2019 editorial con-
cerning electrical safety. Technology has moved on since
Tesla’s AC generation and distribution system was adopted
as a worldwide standard.
The intrinsically hazardous high-voltage AC system is
being rendered unnecessarily dangerous as new solid-state
based technology enables intrinsically low voltage devices.
The voltage of the domestic ceiling lighting circuit can
now be reduced to a few volts, either AC or DC. Much of
the technology incorporated into the new LED lights has
been to cope with the relatively high mains supply volt-
ages, when only about 3.5V DC is needed for the LED(s).
Fan motors could run at 12-24V DC.
Eliminating 230V AC connectors extends the possible
design profiles of globes and luminaires. Fixed switches
need not be connected to the luminaires, making multi-
way switching and other effects a design breeze with a
very low-voltage solid state system.
And why stick with 50Hz? An inductive loop in the ceil-
ing running at 2kHz or so would enable luminaires to sim-
ply clip on with no electrical contacts, and battery backup
is easily added. Isolated from grid supply, lighting has the
potential to become far more reliable. This technology is
with us now and only needs manufacturing implementa-
tion around a new standard protocol.
Brushless battery-powered power tools using 18-68V
DC are breaking the barrier for rotary power devices, Dy-
son has now stopped the development of mains-powered
vacuum cleaner technology.
This smart motor technology is easily capable of being
adapted to a 50V DC in-home power circuits for all ap-
pliances, and 50V is also enough for hot water and stoves
using heavier cables.
So why is an evolutionary migration to low voltage, in-
trinsically safe, home electrical distribution system not
taking place?
I don’t see any manufacturing difficulties in transition-
ing from the old system to a new one but more the legal,
prescriptive nature of building and wiring requirements
in most countries including Australia, discouraging man-
ufacturers from offering such products on an evolution-
ary basis.
Technology has moved so far and so quickly that it could
now be argued that our current prescriptive electrical laws
may contribute to unnecessary future deaths and injuries
from needless electrical hazards.
Kelvin Jones,
Kingston. Tasmania
Nicholas comments: while lighting and some appliances
could run from lower voltages, the current requirements of
many appliances at lower voltages (eg, washing machines,
drivers, ovens, coffee machines) would be impractically
high. In countries with 110-120V mains, some of these
machines are already a challenge to power.
Espresso machines are a good example. Units sold in
countries with 115V mains often need to use less powerful
heating elements to keep the current draw modest. Some
domestic espresso machines need 15A outlets for full per-
formance even in Australia.
Overseas, those same machines do not work as well, not
being able to draw even the 2300W that’s available from
a mains socket here.
Regarding battery-powered vacuum cleaners, I have
found their performance to be inferior to mains-powered
vacuums, suitable only for some jobs. After vacuuming my
car using just a Dyson for a few months, it started smelling
bad. One quick pass with a mains-powered vacuum (no
flat battery halfway through the job!) had it clean again.
I’m not saying low-voltage, battery-powered vacuum
cleaners are bad; they certainly have their uses. But they
are no replacement for a mains-powered vacuum with
much more powerful suction.Tips for soldering battery packs
I have been making up battery packs by soldering (with
great care!) NiMH batteries together. These batteries (like
some other items) are nickel-plated which leads to frustra-
tion, as the rosin flux in standard solder is not adequate
for the job.
Different fluxes suit different metals, and I heard from
someone that phosphoric acid would work as a flux. Phos-
phoric acid is available in dilute form as ‘rust converter’- one common brand available in Western Australia is
Ranex, which is 35% phosphoric acid.
So I decided to try using this as a flux for soldering to
the batteries. Phosphoric acid is nasty stuff, especially
on skin, so safety precautions (gloves, goggles etc) must
be observed. And you need good ventilation, since it can