LUV Meeting July 2008

At the last two meetings of LUV [1] I’ve given away old hardware. This month I gave away a bunch of old PCI and AGP video cards, a heap of PC power cables, and some magnets (which I received for free because they were in defective toys that could seriously injure or kill children). One new member was particularly happy that at the first meeting he attended he received some free hardware (I hope it works – most of that stuff hasn’t been tested for over a year and I expect that some would fail). Also there was another guy giving away hardware, so I might have started a trend of giving away unused hardware at meetings (he was giving away some new stuff in the original boxes, mostly USB and firewire cables).

For a long time (many years) at LUV meetings there have been free text books given away. One member reviews books and then gives them away after he has read them.

At the meeting Ralph Becket gave a presentation on the Mercury functional language. It was interesting to note that Mercury can give performance that is close to C (within 80%) on LZW compression (which is apparently used as a benchmark for comparing languages). Given the number of reasonably popular languages which don’t give nearly that level of performance I think that this is quite a good result.

After the meeting Richard Keech demonstrated his electric car. It’s a Hyundai Getz which has had the engine replaced by an electric motor but which still uses the manual gearbox. Richard did a bit of driving around with various LUV members as passengers to demonstrate what the car can do. Unfortunately I didn’t get a chance to be involved in that, so I’ll have to do so next time I meet him. One thing to note is that Richard’s car was not built that way by Hyundai, it was a custom conversion job. The down-side to this of course is that it would have cost significantly more than a vehicle with the same technology that was manufactured. One design trade-off is that Richard had batteries installed in the place for a spare tire. Last year the RACV magazine published a letter I wrote suggesting that small cars should be designed without a spare tire and that owners of such cars should rely on the RACV to support them if they get a flat tire [2], my option has not changed in the last year, I still think that cars which are driven in urban areas don’t really need spare tires so I don’t think that Richard is losing anything in this regard.

The motor driving Richard’s car runs on three-phase AC and a solid-state inverter is used to convert 185V DC to about the same voltage at three phase AC (I didn’t write notes so I’m running from memory). Apparently on long drives the inverter gets cooler rather than hotter – I had expected that there would be enough inefficiency in the process of converting DC to AC that it would get hot.

In a previous conversation Richard told me that he can drive his car 75Km on one charge and that it takes him 8 hours to charge when using an Australian mains (240V) plug rated at 10A. When designing such a vehicle it would be trivial to make it use a 20A plug for a 4 hour charge or even a two-phase plug for even shorter charging (I’m sure that Richard could have requested these options if he wanted them). But an 8 hour charge allows the vehicle to be completely charged during a working day and the use of the most common type of plug (the type used in every home and office) means that it can be charged almost anywhere (the standard mains circuit used in Australia is rated at 15A so special wiring is needed for a 20A socket). There is such a power point mounted on the outside of my house not too far from where a visitor could park their car. I anticipate that in a few years time it will not be uncommon for people who visit me to charge their car during their visit. Richard’s ratio of an hour of charge to almost 10Km of driving means that someone who visits for dinner could get enough charge into their car to allow for 30Km of driving before they leave. 30Km is about the driving distance to go from my house to a location on the other side of the city that is just outside the main urban area, so probably at least half of Melbourne’s population lives within a 30Km driving distance from my house. Not that I expect friends to arrive at my house with their car battery almost flat, but it does make it easier to plan a journey if you know that at point A you will be able to get enough charge to get you to point B.

I think it’s a good thing to have members of LUGs give things away to other people and to demonstrate technology that is of wide interest. I hope to see more of it.

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