Energy Meter kit is first class

I recently purchased the Energy Meter kit (SILICON CHIP, July & August 2004) from Dick Smith Electronics and I must say what a professional job they have done. I have built a lot of kits in my time but nothing to rival this one. The finished product just looks like it was factory built. It was all so easy. Normally PC board switches have to be mounted a certain distance off the board so they protrude the correct distance through the front panel and the same with the LCD module.

But not with this kit; everything is bolted in and with the spacers supplied, everything came to be an absolutely perfect fit. It was also easy to calibrate, although it takes a long time as the calibration stepping is very slow. It is extremely accurate over the entire range and I can highly recommend it. Congratulations to SILICON CHIP for the design and to Dick Smith Electronics for their effort in producing a superb kit.

Paul Cahill, Rooty Hill, NSW.

Voltage warnings are worthwhile

I would describe myself as a software developer with a passing interest in electronics. Regarding the Publisher’s Letter on the topic of high voltage warnings, I feel it’s a matter of perspective. I think you do a good job of presenting relevant information for your articles. I don’t know what the alternative is but if you are putting colour codes for resistors in articles then why not the warnings?

I have no problems with the PIC projects but there is no way I would have known that the article on the CFL Driver in the same issue (September 2004) was at mains voltage.

If that is the biggest problem in Mr. Hoolhorst’s life then I envy him!

On another note, I quietly cringe at how "nerdy" some of the articles sound. I get the feeling that you engineers are really in a world of your own. Every time I read "she who must be obeyed" makes me think that anyone who says that deserves a wife that annoying!

Another example would be in the September issue – in the article "How To Call Long Distance FREE", Ross Tester says: "Telstra claimed ‘incompatible infrastructure’".

What does he mean by "claim"? To me, that reads "Telstra have said it’s not possible and that the Author thinks that Telstra is not telling the truth." Since he doesn’t say, I would be quietly confident that he is using Optus for his home phone. And since the ISP and the customer have to be using the same telephone network, if they are different, it won’t work.

Apart from that, it’s a great magazine – just a little bit too nerdy.

Christian Payne, via email.

Comment: Ross Tester is not an Optus telephone customer. And as we understand it, the ISP and the customer do not have to be on the same network.

As far as "she who must be obeyed" is concerned, all wives want their husbands malleable, don’t they? And it seems true to us, that people who say that "she must be obeyed" patently don’t!

Kit feedback on the PIC Programmer

I recently purchased a Jaycar KC5367, the PIC/serial EEPROM programmer kit, based on the September 2003 article in SILICON CHIP.

As someone just beginning with PICs, I considered buying a ready-made PIC programmer but chose this kit since it was a fraction of the price of the ready-made ones. As a software-only person, nervous around hardware, I felt timid at the prospect of assembling a kit. As someone who’d dabbled in (mainly analog) hardware as a kid, I well knew how easy it is to make mistakes at any step of the way and get badly lost, and end up taking ages to correct the problem (if it could be corrected).

However, I found this kit – the well-engineered PC board, the clearly-labelled components, the excellently written SILICON CHIP article and supplementary instructions – to be of the highest quality.

Construction and testing took me four hours, much less than the 1-2 days I was expecting. To my delight, my first PIC burn/verify succeeded without incident.

Something else that impressed me was how the Jaycar kit included the expensive 18-pin ZIF socket, plus a 16F84A PIC, making it unbeatable value for money.

So this note is just to say thanks for saving me an absolute wad and giving me the satisfaction of building this crucial tool myself. I’d recommend Jaycar kits and SILICON CHIP magazine to anyone.

David McNab, Auckland, NZ.

Thanks for your very enthusiastic endorsement David. We know that most people get their kits to work without problems but it is nice when someone pays a compliment like this. It is also worth celebrating the fact that our kitset suppliers do us proud and a wide range of these SILICON CHIP kits are now selling around the world.

Sprinkler controller circuit has corrosion risk

I would like to advise anyone who makes the Sprinkler Controller depicted in the Circuit Notebook pages of the October 2004 issue to make sure they know where all the valves are located. This is because there is a strong possibility that they will eventually need to rewire them due to corrosion of the wires.

I previously worked for a company involved in designing irrigation control systems. We found that it was essential to have zero DC on the lines to prevent electrolysis. This was found the hard way. All the wiring in a park had to be replaced. The reason that 24VAC is used is that it does not cause corrosion. The insulation on the wires is usually insufficient to stop the problem.

The corrosion is due to water penetrating the plastic insulation when the cable is buried. It usually takes six months or more to happen. If all the wiring is above ground or in waterproof conduits, then the problem should not occur.

With the PICAXE being so easy to use, I hope many more readers will send in circuits and programs so that others can benefit from their ideas.

Colin Carpenter, Mosman Park, WA.

Big wrap for valve preamp

I just wanted to congratulate SILICON CHIP and Jim Rowe on the Valve Preamp for HiFi (November 2003). I have just been listening to it and I must say I’m amazed.

I had never heard valves before and I had always been curious but until now they had been too expensive to take the chance on. Your valve preamp has made it affordable to try the "valve sound" and I must say the sound I am getting from my hifi system now is superb.

This valve preamp is so musical and an absolute joy to listen to! I really am taken aback at just how much better sounding this preamp is compared to any solid state preamp I have had. It has made my entire CD collection sound more musical. I don’t care that valves aren’t technically perfect; the sound is all that matters and this preamp is a winner. Well done and thank you!

Rob, via email.

Comment: Sound’s musical, eh? Now that’s a worry.

Wide-screen digital TV is a mess

In December 2003, I wrote regarding my thoughts on the current state of Digital TV broadcasting in Australia.

Recently, Aldi started selling their own "Medion" brand digital set-top boxes for the princely sum of $169. I couldn’t believe this low-cost Chinese-made offering: you just plug it in and it works! All the local channels were already tuned in; all I had to do was tell it where I lived and it automatically sorted out the program guide, local time and so on.

You even get an on-screen signal strength meter to help you set up the antenna! The digital channels came booming in! So now it seems I’m getting Digital TV as advertised. If they can just do something about the fact that most of the time all I’m getting is five copies of the existing analog channels, I’ll be ecstatic!

Interestingly, unlike the Thomson units, the Aldi receiver actually does something with the HD transmissions instead of the screen just going blank. You get a series of "stills" which seem to have more resolution than the "live" SD transmissions, although I know that doesn’t really make sense on an SD TV.

The whole HD/widescreen thing seems to be going off the rails somewhat, particularly in the USA. Contrary to what was predicted, sales of widescreen sets seem to have gone off the boil. Most of the newer large-screen TV sets I’ve looked at recently have been standard 4:3, including one "HD-ready" Philips 68cm 100Hz job for $999.

They seem to have somewhat lost the plot with large screens. The Philips set offers a choice of 625-line 50Hz progressive scan, 625-line 100Hz interlace, or 1080/1250 line 50Hz interlace. On 1080/1250, you can hardly see the horizontal scanning lines but the tube’s vertical stripe pattern is considerably coarser than even the plain old 625-line horizontal line structure! "HD ready"? Ready for what? Trouble is, the finer the pitch, the more electrons that wind up simply heating up the shadow mask, and the more power consumed, the heftier the scanning circuitry has to be and so on. Most manufacturers have taken the easy way out.

Very few plasma screens offer true HD 1920 x 1080 resolution; in fact a lot of models have only "VGA" 640 x 480 resolution (derived from the visible picture area of ordinary NTSC transmissions).

Meanwhile large-screen LCD displays are racing up on the inside, offering lower cost, lighter weight, less fragility and lower power consumption. The images aren’t yet quite up to current plasma or CRT standard but I doubt many people would notice the difference. What’s really interesting is that many of them are old-fashioned 4:3, not widescreen 16:9!

This highlights another major stuff-up. As one of your other correspondents has pointed out, if you set your Digital receiver to 16:9 letterbox, a lot of the time you simply wind up with a three-quarter sized 4:3 image, since the stations routinely transmit 4:3 sourced material "vertically letterboxed"! Worse still is vertical-letterboxing of already horizontally-letterboxed SD material!

This is because the authorities blithely assumed that everyone would by now own 16:9 TV sets. What should have happened was a mandate that all digital set-top boxes be fitted with a 16:9 "flag" signal output and all new 4:3 TV sets set up to switch automatically from this. Ah well hindsight, the only perfect science!

Keith Walters, via email.

Compact fluorescents are still worthwhile

Your comments regarding CFLs are interesting, especially in regard to the their claimed lifetime and your less than satisfactory experience. However your comment that they’re "not worth a candle" is surely opinion taking precedence over simple facts.

A $15 price differential will buy 100kWh of energy (at 15c per kWh) and with 60 watts energy reduction, the unit would need a life of about 1660 hours to become cost neutral (about 4.5 hours per day). Subsequent operation will be a small return on investment, which is more than can be claimed for an incandescent globe.

I have had a CFL installed in a study for over two years and would easily spend 4-5 hours per day with the light on. It would be reasonable to estimate over 3000 hours operation. I understand they are not well suited to highly intermittent use, which may account for the failure rates you are experiencing although your suggestion to validate claims is well made.

With the proliferation of inefficient down-lights – and given that if just 100,000 households substituted one CFL in a 4+ hour, 75W situation, resulting in a saving of 8760MWh per annum – it is not sufficient to draw a conclusion that CFLs are a waste of money. Economic decisions need to consider all forms of impact, both on our pockets and the finite reserves nature provides and entrusts us with.

Roland Denholm, via email.

CFL light output not evenly distributed

When compact fluorescent lights were first introduced they seemed like a good idea but at over $30 they were just not an economic proposition. They have been greatly improved in design and lowered in price but as you point out in your Publisher’s Letter in the August 2004 issue, they have not proved to be anything like as reliable as claimed.

I have always been puzzled by the apparently low light output compared with what is claimed. For instance, I have a 20W lamp which is said to give the same light output as a 100W incandescent lamp. Prompted by Energy Australia’s offer of a free lamp, I decided to investigate the disparity a little more closely.

The CFL does indeed emit almost as much light as the incandescent but only in a narrow plane perpendicular to the axis of the tube. Away from that plane, however, the light output rapidly drops off to almost zero on the lamp axis. The incandescent, on the other hand, emits light in an almost uniform sphere, apart, of course, from the region of the base. As a result, I estimate that the total light output of a 20W CFL is about equivalent to a 40W incandescent rather than that of a 100W unit as claimed. The disparity can be overcome in an industrial situation to a large extent by mounting the CFL horizontally in a reflector but this is generally not practicable in a domestic situation.

While there is still a halving of the power input, a 40W incandescent cannot be regarded as producing a useful light output in most domestic situations. I did not take up Energy Australia’s offer!

Alan March, via email.

DC plugpacks that bite

Over the last few years, more and more equipment is powered by plugpacks and as a result you end up with extension boards full of the things. I am a part-time musician and I have a number of guitar effects units which are all powered by plugpacks.

I have been noticing that when I am patching various signal leads, sometimes I get a slight belt (shock). My trusty multimeter tells me there is 9V DC across the plugpack output plug, just as you would expect. But it also tells me there is about 100-110V AC present as well. When I plug the plugpack into any effects unit, then connect a standard guitar lead to the output of the effects unit, when I measure from the shaft of the jack to earth, that is when I see the high AC voltage. I get a shock when I am grounded by touching the case of my power amplifier and the jack when I am patching units together. Everything works OK but this does not seem normal.

I have a number of plugpacks that do this. Also, my HP Deskjet 840C is run off an 18V plugpack. When I plug the parallel printer cable into the computer, you can see a spark as the shell of the printer cable hits the earthed PC case. Again, I can measure a (relatively) high AC voltage to earth, even though the DC output is spot on.

What is going on here? Do I have a wiring problem in my house? I have an earth-leakage gadget back at the fuse box but it never trips.

Neil Macpherson, via email.

Comment: it does seem as though this problem is more pronounced with switchmode plugpacks. They seem to measure around 100VAC above Earth compared to 5-10VAC with typical conventional plugpacks (measured with a typical digital multimeter which has 10MΩ input impedance). This voltage leakage is caused by the intrinsic circuit capacitance between mains Active and the output lead and this will naturally tend to be higher in switchmode plugpacks which do not contain a conventional 50Hz transformer.

Even though this may lead to the occasional "tingle" they all seem safe enough and all should have passed the usual compliance tests. Having said that, we would not be inclined to connect any plugpack to equipment while it is switched on – that seems to be asking for damaged circuitry and the shocks you experience.

Mobile phone numbers unknown

I agree with most of your comments in the Publisher’s Letter in the November 2004 issue, about fixed telephone lines but there seems to be a basic shortcoming with mobile phones. How do you find another person’s mobile phone number?

It is easy to find land-line phone numbers via the "White or Yellow Pages" but there is no equivalent for mobiles. I understand that it is probably impossible to provide one which is up-to-date but there doesn’t seem to be a possible solution.

My observations and enquiries indicate that you have to know someone who can give you the number; in other words, a "grapevine". I also get the impression that most young people use mobiles to talk with people they probably see everyday.

In the case of builders and suchlike, it seems to be common to use the Sensis directory and call their land-line which then re-directs the call to a mobile – you still need the land-line to start the process. I think it would be a time-consuming task to use a mobile to look up the Sensis directory to find a land-line phone number, on a very small screen. Telstra used to advertise how you could access the internet via your mobile but I think they have given up promoting such a difficult task.

Ron Sanders, via email.

Warnings on 240VAC not too cautious

Are you being too cautious with your warnings with 240VAC equipment? (Publisher’s Letter, September 2004)? I don’t think so. The first thing learned to prevent electric shocks is never to make any assumptions. Watch any experienced electrician approach a faulty piece of equipment: even though it will have been turned off and checked with a voltage probe, habit will still force the wise to initially touch it with the back of the hand to avoid a reflexed grasp if shocked.

The editorial refers to 240V mains Active/Neutral transposition. Let me briefly tell you how I nearly lost my life to a situation like this. I trained and qualified as an electrician in South Africa and after migrating to Australia, became employed in the electronics industry and then the entertainment industry. Participating on a film shoot back in the late 70s before earth leakage detectors were in wide use and well before tagging and testing for extension cords was mandatory on film sets and work sites, I was moving live redhead lighting stands around a film set.

On about the tenth attempt to improve the lighting which was by this time a rats nest of multiple extension cords plugged into multiple distribution boxes, I grabbed hold of two lighting stands, one in each hand to move them to a new position for yet another take. This was very nearly the death of me. I found myself with a lamp in each hand and the full 240VAC across my chest and heart. Frozen and unable to let go for what seemed an age, I finally managed to hurl myself free of one of the stands. It felt like hours but I am told it was more like seconds before I managed to release.

After regaining my composure and wanting to find someone to be the focus for the string of obscenities I had been practising, I set out to investigate how the hell the situation had become that dangerous. The studio boss advised me that all the lights and extension cords had been tested prior to the shoot. Testing in those days prior to more stringent regulations meant "plug them in and see if the light works". I began dismantling and testing the lighting rig.

What was very nearly my demise was a combination of two lights on metal stands with frames correctly terminated to the earth pin. One extension cord was correctly terminated while a second extension cord had Active and Neutral transposed. The third extension cord was the killer; it had Neutral and Earth transposed.

The Neutral/Earth transposition in the absence of earth leakage detectors would appear to work properly; ie, "the light would come on" and it would deliver the full 240AC from Active to Earth. The Neutral/Active transposition would have passed the same cursory test. The second and third extension cords produced the potentially lethal trap. So are you being too cautious with your diligent warnings? Not from my experience you aren’t!

Brian Shirley, via email.

Correction: Victor Barker’s letter on page 6 of the November issue made reference to a degausser circuit involving a 150nF charged by a 330Ω resistor. This value should have been 330kΩ.