Halogen lamps are a UV hazard

I noted your dislike of halogen lamps in the Publisher's Letter in the June 2003 issue. Can I put a slightly different spin on the lamps and yet still come to the same conclusion? You were concerned about the 80% efficiency of the transformer. I think you will find if you check it out that the lamps are more efficient light producers than conventional lamps by more than enough to make the transformer/lamp combination more efficient than the conventional incandescent lamp.

They are more efficient light producers because they run the filament at a higher temperature. The amount of light produced in the visible spectrum increases very rapidly for only a modest increase in filament temperature, simply as a function the physics of radiation of hot bodies.

Low-voltage halogen lamps manage to be able to be run at these higher temperatures by a combination of three aspects of the lamp design without the resultant reduction in the lamp life. They run the envelope at a high pressure, they fill the envelope with halogen gas and they use a thicker filament wire. The high pressure and the halogen gas greatly reduce the evaporation of the tungsten while the thicker wire makes for a more robust filament structure. All three contribute to increase the lamp life and to counter the shortened life of the higher temperature.

To handle the very much-increased pressure, the glass must be made stronger. Now the stress in a cylindrical or spherical vessel is a function of the internal pressure and the ratio of the radius to the wall thickness. These lamps have both thicker walls and also smaller diameter envelopes. While this works stress-wise, the very small envelope gets very hot, being much closer to the filament. Ordinary sodium glass would soften and creep, leading to an aneurysm type failure so quartz glass is used.

And this is what upsets me about quartz halogen lamps. Because quartz glass is used, a significant amount of ultraviolet light is allowed to leave the lamp. Quartz unlike sodium glass is transparent to ultraviolet light. Besides the ultraviolet problem, I don't like the idea of a transformer in the roof space, hidden from view and able to possibly start a fire. I also don't like the fact there is or must be significant ventilation around the lamp assembly. After all, is not a ceiling a sealing?

Kenneth E. Moxham,
Urrbrae, SA.

Comment: we agree that halogen lights are more efficient than conventional incandescent lamps but their narrow beam means that they are impractical and inefficient in most domestic and commercial installations.

Linux articles appreciated

Thanks for the excellent series on Linux from November 2002 to February 2003. Even with only a minimal amount of previous Linux experience, I was able to follow exactly the steps described by John Bagster and make something very useful out of an ageing dinosaur.

Fortunately, I was able to dig up the distribution of Linux used in the article (Red Hat 7). I also happen to have the Optus flavour of cable and even live in the Brisbane area - it was as if the article was tailor-made to my situation.

Once again, thanks SILICON CHIP - any follow up articles on this subject would be greatly appreciated.

Dave Rogers,
via email.

Ferrite cores may be hard to get

The June 2003 issue of SILICON CHIP contained an interesting little SMPS and like most SMPS circuits, it uses a ferrite-cored inductor. The core type is described with a manufacturer's serial number and a supplier's catalog number. One day I might build the project. But when I do, it's very likely that the inductor core will no longer be available. The item will be superseded, no longer be manufactured or whatever. So that project will remain unbuilt and I will be disappointed.

I and many of your readers would be grateful if, when publishing articles using such ferrite inductor or transformer cores, you could give sufficient description of dimensions and magnetic properties so that we could get a roughly equivalent component.

Mike Newman,
via email.

Comment: we understand the problem but we really don't think that quoting all the characteristics (if we can get them) will necessarily solve the problem. By the way, we have given two sources for the powdered iron cores and they have been made for many years now. We do try and use components which will be available for years to come.

If you are really concerned about making the circuit in the future, why not purchase some cores now? The kit is available from Dick Smith Electronics, Jaycar and Altronics.

Specifications of PowerUp are misleading

The PowerUp project in the July 2003 has some anomalies with its power ratings. For someone who might pick the unit up, the only guide to its rating is the 10A label on the fuse; a natural assumption if you didn't build it and hadn't read the article.

The specifications in the article state the rating is 6A (set by S1)? The fuse should set the rating. The idea of having a fuse is to protect the other components - with a 10A fuse, the cable (7.5A), the switch (6A) and probably the PC board (about 5A by the chart I use) are not protected against overload. And with nothing on the label to indicate otherwise, the unit is likely to be unwittingly used with loads of 8 or 9A.

Finally what is the purpose of the two 1.2MΩ VR25 resistors across the slave socket?

Andy Williamson,
via email.

Comment: we put the rating of 6A (1440W) in the article for the sake of completeness. Your objection can be met by either changing the fuse to 5A or the switch to 10A rating. Or omitting the power switch altogether. We understand that Jaycar are supplying their kit with a 10A switch.

The purpose of the VR25 resistors is to shunt most of the current which flows through the 1nF capacitor across the relay contacts when the PowerUp is off. Without these resistors, Neon2 would be fully alight all of the time.

Updating the PIC Programmer

I just read your latest review on updating the PIC Programmer, in the July 2003 issue of SILICON CHIP.

I had all sorts of grief with this unit under Windows 2000 and XP. However, in November 2002, the author, Nigel Goodwin, released a new version of the programming software which is called WinPicProgV1.91. www.winpicprog.co.uk

This has an almost identical interface to the original and appears to work quite well. You still have to load the port driver but that's a "one-off".

I am running a 2.6GHz Athlon using Windows 2000 and XP Pro and it worked flawlessly under these. It also worked with Windows 2000 and 98SE on an old 650MHz machine. However, I am still going to try the new programs you listed, just for the hell of it.

Andrew Johansen,
via email.

Digital TV should be promoted

I do enjoy SILICON CHIP but have lately found Leo Simpson's near-Luddite editorials quite depressing. I'll save my feelings on low-voltage halogens for another time but how about being a little more encouraging on Digital TV? Isn't it an inevitability, like the move from analog to digital mobiles last decade?

Sure, it was forced upon us but what are you going to do? March on Alston's office? He does seem to be ill-informed on occasions but DTV is here now. And isn't the underlying reason for the change the more efficient use of the RF spectrum?

I accept most of what you say, apart from the reference to the networks' "low quality" digital service, and the uptake is at odds with Australians' usual rapid acceptance of new technology. But I believe you should be encouraging the system because it is inevitable and it is a superior format. Standard Definition is definitely NOT a "low-quality digital signal", except perhaps on paper.

Spend a week with wide-screen Standard Definition and you won't want to go back. I've lived with DTV for a few months and I love it. It is (subjectively) a superior image to analog and I do get a very good analog signal to compare with.

My young family enjoyed the extra ABC channels and more fool Alston for not helping the ABC financially on that score. Extra content does cost and that includes the "multi-view" concepts. They are possible but for now are just sales hype, as you implied.

I'm not convinced that HD was really a necessary inclusion in the DTV spec; it's perhaps a little too esoteric but we shall see. I feel that the move to DTV is akin to the move from vinyl to CD (audiophile sensibilities aside) or VHS to DVD. I say "akin" not "the same as"; it's a question of degree.

I may be in the 1% you quote but I do have friends with DTV. Digital TVs are expensive, set-top boxes less so but still not something you buy on a whim. But rather than sitting around with your "circle of friends and acquaintances" making your dogmatic pronouncements on the "complete failure" of DTV with a supremely irritating "told-you-so" arrogance, how about promoting its benefits and encouraging it as a viable, and inevitable, alternative?

David McCarthy,
Crows Nest, NSW.

Comment: sorry you think Leo Simpson is a Luddite but it is better to air these aspects of technology rather than ignore them. On the positive side, set top boxes are dropping in price but you still need a set-top box for each set in your household and another to record to a VCR, if you want different programs on each set.

DVD aspect ratios are irritating

I can sympathise with Neil Smith (Mailbag, July 2003) on the narrow strip of picture that comes with much of the DVD picture media. Our family recently purchased a DVD player to use with our 4:3 TVs, only to be disappointed when the first two DVD movies we bought were 2.35:1 aspect ratio, which meant half a picture, so we returned them for a refund.

The Internet has a lot of information on this issue and it seems the movie purists, not the big companies, are dictating that DVDs be available with the picture theatre aspect ratios like 1.85:1 and 2.35:1. One site had mention that during film production most of the action is 'framed' at 16:9 (aspect 1.78:1) in the knowledge that the film will eventually end up on wide screen TV.

Some DVDs - I've never found one - are produced double-sided, with 4:3 or 16:9 on one side and original theatre aspect on the other side. If the DVD media is anamorphic (see www.thedigitalbits.com/articles/anamorphic/ for an explanation), you can set the DVD player to 16:9 instead of 4:3 letterbox which gives the actors elongated heads but for some of us this is preferable to large black zones.

Except for the titles there was never a problem with the old Cinemascope films that ended up on videos. Surely in this day and age there can be a compromise so that all sections of the consumer market can be kept happy - and buying DVDs.

Barry Jorgensen,
Cromer, NSW.

Today's electronics not environmentally friendly

Today, people think we are being more environmentally friendly because of the efforts to increase recycling. In the world of consumer electronics this is not so. In fact, we are much more environmentally damaging with TVs, stereos and boom-boxes being less repairable today compared to decades ago. To be more environmentally friendly, the manufacturers should make their appliances with cabinets carefully designed and with simpler circuitry to make servicing easier.

I have seen very simple electronic schematics in televisions, boom-boxes, etc and they still perform well. I have even seen TVs that had circuit boards mounted on hinges so the boards can swing out to make things in the sets more accessible. Manufacturers may be taking this approach for profit but look at the dumps. You would be surprised how much electrical rubbish appears at the tip everyday.

My guess is that TV servicemen must be worrying how much electronics there would be in that single "beyond economical repair" television that would be a threat to the environment. Manufacturers should change their ways to create less landfill and more jobs for servicemen by making repairs to appliances more possible.

Chris O'Reilly,
via email.

Comment: there are two cost pressures at work here. Mass production and imports from Asia are inexorably reducing the cost of consumer appliances while the cost of labour for servicing and the cost of maintaining spare parts inventories continues to rise. Inevitably, as time goes on, more electronic equipment will be uneconomic to service. Whether it is practical to recycle old equipment again comes down to economics.

Digital TV is a spectrum grab

Regarding your editorial in the July 2003 issue about the failure of digital TV, this is simply another example of what happens when technically illiterate bureaucrats get into bed with vested interests!

In the 1920s, we had a brand-new 20th century technology (radio broadcasting) being managed by 19th century politicians. We wound up with the infamous "sealed set system" and higher power and lower frequencies reserved for so called "A-class" (government) stations.

Then after many years of conveniently nobbling any possibility of FM broadcasting in Australia by the ingenious tactic of suddenly sticking extra TV channels in the international FM band, FM services were finally announced in the early 1970s - originally to be on the UHF band!

Again after several years of successful outback satellite TV broadcasts on the 4GHz C band, the Government suddenly decided we needed to switch to horrendously expensive and technically dodgy B-MAC on 12GHz. Why? Well, I think that had a lot to do with rumours that certain organisations were thinking of setting up a commercial pirate TV service, targeted to Australia but operated offshore.

Preventing local firms from advertising on such a venture would be a legal and political nightmare and in light of the CB radio experience, so would prohibiting the sale of C-band receivers!

Now we have Digital TV. My own experiences of this (mostly setting up receivers for friends) has been pretty dismal. In one case, the Thomson receiver was completely unable to tune in the ABC or SBS transmissions, despite the analog versions being received with good strength on the same antenna. And with typical Gallic arrogance, the box gave no clue or explanation as to why and there's no manual tuning option. It also rewards you with a completely blank screen if you accidentally tune to an HDTV transmission.

And what do you get for your trouble? Most of the time, Channel 7 and Channel 9 just give you five copies of the analog channel. Channel 10 just gives you one, plus four still slides.

But why, after nearly 50 years, do we so desperately need digital broadcasting now? The fact is, the Government doesn't care about the kind of pictures we watch or their quality. They're just like a lot of greedy relatives trying to push grandma into a nursing home "in her own best interests", when all they really want to do is get their hands on the family mansion. Only in this case the family mansion is a couple of hundred Megahertz of electromagnetic spectrum that they're positively salivating to auction off to the highest bidder, once those tiresome analog TV broadcasts have been put where they belong.

Adrian Kerwitz,
via email.