4 Silicon chip Australia’s electronics magazine siliconchip.com.au
New Zealand 433/434MHz
transmitter legality
For your information, the New Zea-
land Short Range Devices (SRD) Gen-
eral User Radio License (GURL) men-
tioned in your article on the 433MHz
UHF Data Repeater in the May 2019
issue has been superseded. The new
one is at: https://gazette.govt.nz/notice/
id/2019-go
The changes are listed at the bottom,
none of which affect the 433MHz band.
While you can operate SRD repeat-
ers under the GURL, the device still
needs to meet the applicable standard
at a minimum (which can be found at
https://gazette.govt.nz/notice/id/2016-
go2007).
More information for the require-
ments can be found at siliconchip.
com.au/link/aaqa and it would be at
level A1. The supplier would be any-
one who manufactures a unit.
Jeremy Logan,
Radio Spectrum Management,
Ministry of Business, Innovation &
Employment
Wellington, New Zealand.
Electrical safety should
be taken seriously
Silicon chip is, without doubt, the
best electronics magazine worldwide;
I look forward to mine every month.
With regards to your editorial in the
February edition regarding servicing
of electronic equipment, I always sug-
gest using a workbench wired via an
RCD breaker as an absolute safety ne-
cessity. Further, all equipment on the
bench to be serviced, or currently be-
ing serviced, should be powered via
an isolation transformer with a single
AC outlet for the appliance under test
(no Earth pin).
All mains-powered bench test gear
should be checked for electrical safety
each year (according to AS/NZS 3760,
or 3000).
All these precautions will not neces-
sarily protect from fatal electrocution,
or even accidents occasioning burns or
secondary damage (such as a fall fol-
lowing an electric shock).
Anybody considering building
mains-powered devices described in
the magazine needs to read, take heed
of and understand each of the safety
warnings, as well as how to put them
into practice for their personal safety. If
in doubt, ask your local electrician, or
do a short electronics training course,
with an emphasis on electrical work-
ers’ safety.
Rod Humphris,
Ferntree Gully, Vic.World’s Largest Flip-dot Display
Made in Australia
As a very long term reader of your
magazine, I always look forward to
reading each issue every month. I en-
joy the wide topic range and level of
technical detail in each article. Keep
up the good work!
I’m not sure if it is in your scope,
but I think that at least some readers
may be interested in what our local
Australian companies are doing on the
local and world stages. As an exam-
ple, the Flip-dot project in your April
issue immediately made me think of
the world’s largest flip-dot display we
built for a large multinational compa-
ny in Atlanta (USA).
It’s 38m wide and 6.6m high with
55,860 dots and incorporates over
4km of cable. To flip all dots at once
(in 100ms) takes 47kW! You can see
a video about it at: http://youtu.be/
UOwHlk4lM2c
We’ve made several huge displays,
including True-Corp in Bangkok (
x 3m), Telefonica in Barcelona (10 x
3m) and are currently working on one
even bigger than the above!
Our primary focus has been big vari-
able message signs for roads, but we
design and make many other things.
We design and build all our ownelectronic assemblies and completed
products.
We don’t manufacture in China – or
even buy components or assemblies
from China. We are proudly Austral-
ian and do everything to make it here.
You can check out our website to see
some of the other things we do, and
happy to answer any questions. See:
http://www.adengineering.com.au/product/
flip-dot-signs-variable-message-signs/
Peter Harris,
Director, A.D. Engineering
International Pty Ltd,
Gnangara, WA.Stoked about geophone seismograph
I just picked up my April edition
of Silicon chip magazine and there
on page 80 is a Tim Blythman article
entitled “Using a geophone with our
Arduino seismograph”. The article be-
gins, “Reader Michael, from western
NSW, kindly sent us a model 20DX
geophone sensor, suggesting that this
would be a great add-on to our seis-
mograph project”.
I’m really stoked that Tim Blyth-
man picked up my suggestion to add
a geophone and now I think the unit
is definitely worth building. What es-
pecially impressed me with this par-
ticular Arduino design is the idea of
logging seismic data in 4-channel WAV
file format.
The MEMS accelerometer used in
the earlier design is great for strong
motion detection, but not weak local
quakes. Viewing and editing WAV data
is easy with Audacity or similar soft-
ware, and since it’s already a sound
file, one can have fun listening to sped-
up seismic signals and the like.
The only thing missing is the addi-
tion of precision timing with a GPS
module, but I suspect that could be
achieved relatively easily by an Ar-
duino whiz. With precision timing,
one could set up arrays of the things
to log and localise events, and studyLetters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that
Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to
submissions to “Ask Silicon chip”, “Circuit Notebook” and “Serviceman”.MAILBAG
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