Practical electric vehicle wanted

I wish to congratulate you all on a mighty fine magazine. I am wondering if you would ever consider designing a project for a practical electric vehicle, using an ordinary 3-phase AC induction motor and an inverter power supply, possibly with IGBTs and controlled by a PIC. AC induction motors have the advantage of having no brushes and are easily obtained. PICs have all the advantages that you already know about!

Ian Horacek, Melbourne.

Comment: we have often mulled over the idea of a designing an electric vehicle using, as you suggest, a 3-phase induction motor and a variable frequency/variable voltage supply, possibly running from a 240V battery bank (no inverter required and we’d use an American 220V 3-phase motor, rated at several horsepower).

Even so, this would be a major engineering exercise, and more so if you wanted to incorporate dynamic braking and regeneration. That’s why we have only thought about it, rather than actually doing anything. The approach used in golf buggies etc, using a DC motor, is much more practical.

Widescreen on DVD, PAL vs NTSC and DVD Zoning

As consumers, are we being conned with the hype of widescreen format, especially on DVD? Why I am asking this is because I was at a friend’s place a few weeks ago watching ‘What Women Want’ on video. It was in 4:3. A week later I hired it on DVD. I accepted the fact that this was presented in 16:9 wide-screen format but as the movie progressed I realised it wasn’t widescreen at all. It was just the 4:3 picture with black bars top and bottom. When I returned the DVD to the video store I had a few words to say to the staff, not at them, but about the industry. I then asked if I could get a comparison done in store and they saw what I saw.

Out of curiosity, when Channel 7 screened Titanic recently, I did the same test as the DVD is in 2.35:1. Again the DVD had less picture top & bottom; ie, foreheads chopped off, etc.

I thought widescreen was supposed to give more picture on the sides, not less picture top and bottom. On the point of 2.35:1, is there something special about 4:3 as 16:9 is [4:3] 2 and 2.35:1 is very close to [4:3] 3?

Getting back to my gripe, as a result of this cropping we appear to be losing 25% of the DVD picture to black bars in 16:9 and 44% to 2.35:1, so am I correct in saying that when a 2.35 picture is enlarged to fit on a widescreen TV, the resolution would be 56% of the supposed 500 lines or about 281 lines?

On another issue, in broadcasting, PAL is 625 lines while NTSC is 525 lines and claims are made of how superior the PAL picture is. When it comes to DVD or Standard VHS, how can the same claims be made. With DVD, 500 lines is 500 lines, be it PAL or NTSC, and 250 for VHS. Wouldn’t that give NTSC the edge, as it has 30 frames per second to PAL’s 25?

Australia is a PAL country, though I am noticing more and more DVDs for sale in the NTSC format. Is this because Zone 4 includes Mexico, which uses NTSC, and we are receiving their overflow? Maybe I’m missing the point and require therapy, or am I right and brave enough to speak out?

Simon Kareh, via email.

BWD 820 oscilloscope schematic wanted

My faithful BWD 820 oscilloscope which must be late 70s vintage refuses to sync to any source, even its own calibration square wave. On inspection, it is easy enough to identify the relevant section although a quick meter check of components reveals no culprit.

Before I embark on the arduous task of tracing the circuit, I wonder if any SILICON CHIP reader has a schematic or know where I could get one?

John Hansen, 12 Maskells Hill Rd, Selby Vic 3159.

vcontrol@ozemail.com.au

Unnecessary licensing is not the answer

I have just read the discussion in your magazine for July on electric wiring and thought I would submit my view. If Australia is ever to become the "Clever Country", it must be through education of the population in the correct techniques and safety procedures in multi-discipline fields which include electrical wiring.

In my opinion, unnecessary licensing is not the answer to accident prevention in the gamut of "Occupational Health and Safety". We license those that drive motor vehicles, marine licensing and pilots to fly aircraft, etc and accidents still occur in abundance in all of these areas.

It is in the education of the people in correct procedures as in New Zealand and other countries and not by restrictive licensing. If we continue down the let’s "license everything" path, Australia will not be known as the "Clever Country" but as the "cow’s tail" of the world – always behind.

C. Bird, Anstead, Qld.

Electrical regulations are highly discriminatory

Let’s hope the campaign to change the electrical regulation works so that the discrimination ends!

Personally, this is a very big threat, being qualified in electronics and having received extensive training locally and overseas to handle LV, MV and HV systems (from 6V to 32MeV) as part of the job when working on medical diagnostic imagining equipment. I have in my time worked on substations, computers, radio, rewound 6.6kV DC and AC motors used for railway locos – the complete range of "volts" – and I am aware of the "bite" you can get. Yet I see it as discriminatory that I am effectively not allowed to do what I have been trained to do, because of some less than sensibly thought out legislation.

This borders on the ridiculous, just the same as I faced trying to get an electrical licence. I asked the chief Electrical Inspectors office how I could get registered as an electrician and was sent packing, as I am too old to do an apprenticeship. Apparently this is the only way I can get a licence!

How discriminatory, as I wanted to set up my own business and felt I would "do the right thing" and get licensed. No go. I can do the work but have to have a registered electrician come and check it over. Some of them have never seen the inside of 66kV substation let alone gone in and cleaned up the mess after one of the switch racks blew up!

I hope your campaign bears fruit.

T. Bradley, Ferntree Gully, Vic.

People should not do
their own wiring

I have been reading your publication for 15 years. Nothing struck me as being quite so silly as the idea of people undertaking their own house wiring and repairing their own appliances. In the time I have been an electrician, I have witnessed some amazingly dangerous handywork after someone has" had a go" at something and then brought it to me for correct repair. As for the service technicians, just because you work on TVs and videos does not mean you can work on consumer power safely.

To become an electrician, as you know, takes four years of study and practice and I can assure you that there is much to learn. This is not withstanding industrial electrics, which is another world entirely. I feel a bent towards slander at some of the replies I have read toward electricians from your tech readers but I can assure you if you don’t know what you’re doing, as with anything, you can come unstuck badly. What I would also like information about is the insurance company’s point of view on an unqualified person doing the wiring. Will they cover you?

I for one would not undertake any work on a premises that had been wired by an unlicensed person, insurance and personal safety being foremost to my mind.

Just in closing, my personal favourite is the one where Joe Bloggs makes his own extension leads and gets the Active/Neutral around the wrong way. He claims it’s fine as the lead works anyway. If you want to work on certain things, at least get a restricted electrical licence for that purpose, so you are at least conversant with what you’re doing.

Before you techs jump up and down, remember that dealing with 0.5A requires a different mindset than dealing with 50A. Bet you don’t print this.

Peter Raffaelli, via email.

Comment: 12 months ago, we would have mostly agreed with you but the fact that New Zealand, most of Europe and the US allow people to do their own wiring shoots your whole argument to pieces.