This is only a preview of the November 1999 issue of Silicon Chip. You can view 34 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "A Speed Alarm For Cars; Pt.1":
Articles in this series:
Items relevant to "Railpower Model Train Controller; Pt.2":
Purchase a printed copy of this issue for $10.00. |
PUBLISHER’S LETTER
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Production Manager
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Peter Smith
Ross Tester
Rick Walters
Reader Services
Ann Jenkinson
Advertising Enquiries
Rick Winkler
Phone (02) 9979 5644
Fax (02) 9979 6503
Mobile: 0414 34 6669
Regular Contributors
Brendan Akhurst
Rodney Champness
Garry Cratt, VK2YBX
Julian Edgar, Dip.T.(Sec.), B.Ed
Mike Sheriff, B.Sc, VK2YFK
Philip Watson, MIREE, VK2ZPW
Bob Young
SILICON CHIP is published 12 times
a year by Silicon Chip Publications
Pty Ltd. A.C.N. 003 205 490. All
material copyright ©. No part of
this publication may be reproduced
without the written consent of the
publisher.
Printing: Macquarie Print, Dubbo,
NSW.
Distribution: Network Distribution
Company.
Subscription rates: $69.50 per
year in Australia. For overseas
rates, see the subscription page in
this issue.
Editorial & advertising offices:
Unit 8, 101 Darley St, Mona Vale,
NSW 2103. Postal address: PO Box
139, Collaroy Beach, NSW 2097.
Phone (02) 9979 5644.
Fax (02) 9979 6503.
E-mail: silchip<at>siliconchip.com.au
ISSN 1030-2662
* Recommended and maximum price only.
2 Silicon Chip
DC power in the home;
it could be made to work
Last month’s Publisher’s Letter about the
possibility of DC power in the home triggered
off quite a response from readers. Some raised
the obvious safety issues of the difficulty of
safely switching high voltage DC and the possibility that a DC shock can be more dangerous
than AC. These drawbacks must be admitted.
Others though, saw the potential in the idea
and went on to expand the concept.
My feeling is that most people have such a
reliable 240V AC supply that they would never
contemplate ever having any other system; it
works, why fix it? For those that do have an unreliable mains supply, and
I include myself in that category, the occasional inconvenience might be
extremely irritating but it would not justify the investment and time necessary to eliminate it. And whether a DC power system would be the way to
go would probably be a moot point.
However, for those who are in remote locations far away from any mains
power supply, a combination high and low voltage DC system based on
solar arrays could be made to work. As one of our readers points out in the
Mailbag pages this month, quite a few appliances could be made to work
on DC. But would it be safe?
Now that the problem of high voltage DC switching has been highlighted,
could be it be overcome? The answer is yes. But it would not be necessary
to have large mechanical power switches to turn the appliances, lights or
whatever, on and off. The logical approach would be to have electronic
switching which could cope with high voltage DC and AC. This would be
pretty straightforward, when you think about it.
After all, many appliances these days do not rely on mechanical on/off
switches; they use electronic switching. Virtually any appliance which comes
with a remote control uses electronic switching. The same point applies to
microwave ovens, many washing machines and dishwashers. An electronic
switch based on a power Mosfet or IGBT (insulated gate bipolar transistor)
could be made to handle the switching job for AC and DC. So a compact,
reliable and rugged power switch is not an insurmountable problem.
Nor is the problem of automatic degaussing for TVs and computer monitors
running from DC insoluble - there has to be an electronic solution.
So as I remarked last month, there is no reason why most appliances
could not be made to run on 250V DC. Will it ever happen? Probably not.
To be realistic, if you were faced with providing power in a remote location, the most practical approach would probably be to power as many
appliances as possible at 12V DC and for those that cannot be run from
low voltage DC, use a 12V DC to 240VAC inverter which would only run
when an appliance was switched on. Many of the bigger inverters already
have an auto-sensing feature and it is very worthwhile because it stops the
inefficiency of running inverters continuously.
Leo Simpson
|