42V car electrics a labour hazard

Your article on 42V car electrics in the November 2004 issue was most enlightening (no pun intended). However, it brings to mind possible problems with regard to the qualifications of people.

In Queensland, there is a specification for ELV (Extra Low Voltage). To the best of my knowledge, this is defined as 32V AC. At or below this ELV, no licence is required to install or maintain wiring and equipment. Above this voltage, an electrician’s licence is required.

The ELV specification allowed the installation of 32V electrical systems in remote homesteads, etc. I wonder what the licensing authorities will make of the 42V DC systems in cars. Will all motor mechanics have to have qualifications as electricians?

Brian Clancy,
Roma, Qld.

Comment: no doubt the poor misguided Queensland authorities will seek to put some further hobbles on industry there.

Unwired coverage map not real

I read Ross Tester’s November 2004 report on the "Unwired" wireless broadband modem with considerable interest. A quick check on the "Unwired" website revealed that I was in a "pink" area; ie, one with sufficient signal for reliable operation. I purchased a unit.

Alas, despite diligent efforts, I
could not detect a signal in my computer room, nor any other convenient locations. Murphy’s Law prevailed, however, and I obtained a weak, intermittent signal in a most inconvenient location!

I called the technical hot-line and it became apparent that my modem transceiver was capturing a tower in Lidcombe in Sydney, approximately 15km from my house, bypassing two nearer towers. No matter what we did, we could not encourage the unit to capture the nearest tower (in Ryde) and secure a more reliable signal.

On reflection, it became clear to me that the pink – "so you can purchase" region is simply a computer-generated "prediction" of the coverage area. It probably has some basis in theory but actual signal strength? Unlikely. A look back at the relevant website page reveals quite a few disclaimers!

I love the idea of high-speed Internet access. I just hope that many of your other readers do not waste their time as I have.

Gary Johnston,
Hunters Hill, NSW.

Rural mobile phone coverage is poor Re your editorial entitled "Fixed Phone Lines No Longer A Necessity" in the November 2004 issue. Widen your horizons a little. Out here in the rest of Australia, mobile phone service is at best patchy and for anything like internet without landlines, you had better have really deep pockets and very long arms. We actually live on Highway A32 (the only one from Adelaide to Sydney through Broken Hill) and in this town mobile phone coverage is essentially non-existent. How about helping the rest of Australia with your editorials instead of painting a silly and very misleading picture of everything being just peachy? Art Clarke, Manoora, SA. Comment: The editorial is in no way an endorsement of mobile phone coverage in the country. For those people who do have a reasonable mobile phone service where they live (and the vast majority do), the editorial is correct and is backed up by Telstra’s own recent report that fixed line revenue is falling. As you state, country coverage is poor and unwired broadband services in rural areas may never happen.

Hidden danger in autotransformer connection

The circuit shown in the November issue page 86 is very elegant. However, there is one very important warning which I was given over 30 years ago when I tried the same arrangement for work. If one of the primary leads comes adrift with the secondary still connected, then the voltage on the loose wire will be the voltage drop across the secondary winding multiplied by the turns ratio. This could be a very high voltage in the order of a thousand volts with a 20 to 1 turns ratio.

This is another reason to enclose the transformer in a secure box. My design was refused for safety reasons.

Paul Niehoff,
Blackburn, Vic.

PICAXE pin terminology justified

Following the recent discussions over port/pin/leg terminology (See SILICON CHIP, November 2004, page 92) I would like to provide some background to the situation.

The first microcontroller BASIC language was developed by Parallax for their Stamp system around 1992. They used the word pin within input decisions such as ‘if pin0 = 1 then’. Unfortunately, this has now become the universal standard used within at least a dozen microcontroller BASIC applications that I am aware of.

We don’t particularly like this terminology but unfortunately it has become the standard that most users expect. Note also that the word PORT has a different usage within this original BASIC language and so cannot be used.

Within the PICAXE system, we have always provided an alternative to the BASIC terminology ‘pin0’ in the form of ‘input0’. Therefore users can type ‘if input0 =1 then’ to achieve the same task as ‘if pin0 = 1 then’. This is our preferred terminology that we tend to use in our educational datasheets when possible. It is of interest to note that most other BASIC languages don’t even offer an alternative as we do.

Due to the historical confusion over the term pin (which is beyond our control), we took the decision to not to refer to ‘physical external pins’ via the term ‘pin’ within our educational projects as we felt it could confuse the target audience (13-14 year olds). I feel using the term ‘leg’, although not necessarily "professional", does correctly describe to a 13-year old child what we are talking about (without any confusion over the term ‘pin’).

I fully appreciate that electronic engineers may not like the ‘leg’ term but we believe it is in the best interest of the target audience of the educational worksheets. Within SILICON CHIP I fully understand why you and your readers would prefer not to use the term ‘leg’ and so I would recommend that in the future authors talk about ‘physical pins’ and use the terminology ‘if input0 = 1 then’ in programs. This avoids any historical ‘pin’ word confusion which, unfortunately, is beyond our control.

Clive Seager, Technical Director,
Revolution Education Ltd.

Electric fence revives battery

I have recently revived a discarded car battery by connecting it to an electric fence for a month. Maybe this is old hat. Before the fence treatment the battery would not retain enough charge to start a car overnight. After treatment it retains charge for a week.

A month might seem a long time to wait for a result but hey, it doesn’t cost anything.

Frank Murphy,
via email.

Comment: that’s interesting. It is similar in concept to the Battery Desulphator circuit published in the February 2003 issue.

Upload/download discrepancy causes problems with VoIP

Thank you for publishing that informative article on VoIP internet telephony in the September 2004 issue. Telstra should be quaking in their boots! However, those readers who like me are still waiting for broadband to become available might be well advised to check their dial-up connection speeds in both directions before rushing in. With many service providers and Telstra/Bigpond in particular, there is a large discrepancy between download and upload connection speeds.

When testing the "Skype-Out" internet telephone operation on my system, I could hear the other side (downloaded) clearly after a short time delay (0.5 seconds or less) but in the other direction there was a time delay of several seconds – up to 10 seconds in effect and very often it was broken up or garbled. I tested this by ringing up my own mobile phone from the internet phone.

Having an alternative service provider to Bigpond, I tried that as well and I was having much better results although there was still a noticeably different time delay between the transmission directions. I think the bottom line is: use broadband if you want to use internet telephony and ask your service provider about the difference in upload and download connection speeds before signing up.

Gunter Seidel,
Alice Springs, NT.

Fixed line phones lower in cost I would like to comment on some of the points raised in your editorial and the article on wireless broadband in the November 2004 issue. The suggestion that having only a mobile phone is cheaper than a fixed line phone certainly isn’t true for me and my family. I looked at my most recent phone bill and worked out what it would have cost if we had made all our calls (excluding dial-up internet) by mobile. The cost came to more than three times what we paid for making the calls on our fixed line phone, including line rental, etc. I looked at a few different mobile plans – not just the pre-paid plan we have on our mobile but none came even close to being comparable to the fixed line cost. I find it rather objectionable that someone would choose to have only a mobile phone and then expect me to pay the high call cost if I want to call them from my fixed phone. This is especially so with businesses. If I’m looking for a particular product and have a choice of companies to call, those that only give a mobile phone number don’t get my call, especially if I need to ask lengthy questions about the product, etc. I’m not so sure that Telstra should be so worried by the increase of wireless communication since their wired network is still needed. After all, if I use my mobile to call another mobile on the other side of the city, the "wireless" part of the signal path is quite short – from my mobile to the nearest base station and from the nearest base to the phone I’m calling. The signal is still mostly carried by the copper and/or fibre-optic network. I would imagine that the wireless broadband internet system would be the same. An employee of Telstra once quipped to me, "Optus is our biggest customer". Is there enough spectrum space available? If we all decided to ditch our fixed line phones, our ADSL and cable internet and go wireless, would there be enough spectrum capacity to cope or would spectrum pollution rise to the point where the system became unreliable? I belong to an organisation that uses wireless microphones on the PA system at our meeting place. A visitor from the USA said that over there people are abandoning radio mikes and going back to cords because spectrum pollution is making wireless mikes too unreliable. I realise that the analog FM system used on radio mikes is different to the sophisticated spread-spectrum digital systems of today’s wireless communication networks but I still think that the more wireless gadgets we embrace, the more cluttered and noisy our spectrum space will become. Ray Chapman, via email.

Wanted: a laptop with a bright screen

On the front cover of the November 2004 issue there is a picture of a man using a laptop computer in bright sunlight with an obviously very visible colour screen. Are you able to tell me what brand the computer is and the type of screen please?

I ask the question because I have a back porch where I would like to go on nice days and be able to do computing and soak up some of the supposedly useful reflected sun’s rays! Two previous laptops did not perform well in the bright light; they were back-lit screens.

My present desk-top computer is a powerful machine, as I use it for graphics, photographs and text. I know there are laptop computers out there which are just as powerful as this one but I am principally interested in what appears to be an outstanding screen.

Eric Jamieson,
Meningie, SA.

Comment: Oops! We’ve been caught doing something that photographers and graphic artists have been doing for many years – artificially embellishing video screens.

It’s done to just about every photograph you ever see, in newspapers and magazines, of any type of video monitor, including TV sets.

The reason it is done is that it is very difficult to adequately photograph a monitor with its screen on and get a good result for both the monitor (in this case a computer) and the screen. You have to overexpose significantly to get the screen detail which of course doesn’t make the rest of the picture look much good.

Therefore, two exposures are taken, one of the screen and one of the rest, with computer software used to marry the two shots. Or if it’s a computer monitor, it’s likely to be a "screen capture" that is dropped in, rather than a second photographic exposure.

In the case of the cover you are talking about, the image on the screen in direct sunlight was very subdued, as you would expect. So as far as your enquiry is concerned, that computer won’t do what you want. It’s on a par with most other laptops/notebooks as far as brightness is concerned.

TVs should have digital tuners

Keith Walters has quite correctly described the mess that is digital television (Mailbag, December 2004 issue). But there are other aspects of the situation which I find quite as bizarre. How is it that, nearly three years after the introduction of digital TV, very few receivers are sold with digital tuners? Even if you pay thousands of dollars for a big plasma TV you will still be expected to accommodate another box to house the receiver.

As it happens, my personal gripe is not with the display as I can’t afford a big screen set and I am happy with my 28-year old 4:3 set. I have a digital set top box which has proved to be an excellent investment to avoid the intermittent electrical interference which often spoils my reception of the VHF channels. But I also like to record broadcasts for time-shifting. Although I have a DVD recorder and a recent-model VCR, neither has a digital tuner and neither can record the output of the set-top box using its timer.

So either I use the timer to record broadcast plus interference or I have to be on hand to press the record button when using the digital signal. How stupid is this?

The Federal government has done its best to cripple digital TV and it seems to me that it has been aided and abetted in this task by the equipment manufacturers.

Sometimes life gives us an unexpected bonus. I bought the set-top box to avoid interference but I was delighted to find that I could use it to fill the screen with a 600-line picture instead of the 500 (or less) that the broadcasters expect me to use. Mostly it doesn’t matter that I lose a bit at the sides of the picture.

Similarly, I replaced my old VCR because I was fed with having to reset the clock every time we had a momentary power cut. The new machine holds its settings for three years. But I find it has a couple of other useful features. I never expected to use the "extended play" setting but during the Olympics it was useful to record up to nine hours on 3-hour tape and play some of it the next morning with quite reasonable quality.

And the indexing feature which locates the beginning of a recording rapidly and accurately is really useful. It may be a mature technology but it still has a lot going for it.

John Neate,
via email.

RFID implants While reading the Publisher’s Letter in the December 2004 edition, I was amazed that anyone could seriously entertain the idea of implanting RFID chips into people. Human nature being what it is would mean that this technology would be exploited by various groups in society, leading to an era of inequality and discrimination not seen in this country before. If the chips were made mandatory, either as an implant or built into a smart version of a driver’s license, two things would be guaranteed to happen. First, the government would ultimately end up placing RFID readers in every public place to help with "the war on terror", raising the question of why they would want to know where everybody is all the time. More of an issue would be the use of RFID readers by business. There would be companies that would pay shops to place the readers in every store and allow them to collect data on what shops you go to and what and how often you buy. Before anyone talks about legislation only allowing the government to access the data, financial institutions would call for the data to stop credit card fraud, prove ID, etc and most probably they would get it. This data on your spending habits would be used to push products that you may be interested in (although not necessarily needing or wanting). Imagine going into a car dealer, only to get an SMS about a "special limited time only" finance deal. If you think telemarketers are bad now, then this may be your worst nightmare. With an RFID system, you have no control over who reads your number and the associated data that marketing companies may have collected. At the moment, you can choose whom you give this data to but with an RFID tag under your skin you most definitely can not. Having a form of identification that can be read without your knowledge or consent would open a vast array of issues that would make even George Orwell cringe. Jay Herbert, via email. Comment: like it or not, marketing companies already have lots of data about you and your socio-economic group and they use it however they wish, without any choice by you.

Halogen lamps and UV

I want to comment on previous discussion about halogen down-lights and their high UV content (see page 109, November 2004 issue). I needed some UV to harden some plastic. I went to the major hardware retailer and could only find covered dichroic lamps in stock.

Single 12V 50W halogen lamps were labelled as zero UV. I purchased a 240V 150W halogen lamp but when tested, zero UV was present. Amazed at this, I eventually found an old uncovered dichroic lamp mounted in the ceiling and it proved to have significant UV output. The manufacturers must have changed the glass type to eliminate the UV. The moral of this story is that things change.

Leigh Brown,
via email.