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COMING EVENTS:

AUGUST 8 MEETING - SOLAR TECHNOLOGY: On Friday August 8 in “Cottage B” at the WEA 223 Angus St Adelaide there will be a presentation and demo of a number of items relating to alternative energy including solar panels, controllers, and electric motorbike. More details to come.

GENERAL ITEMS:

PICAXE WORKSHOP: On a weekend after late August it is planned to have another PICAXE workshop for kids and their parents. This time it will be held at the Science Centre at the old Hindmarsh Council Building, Milner St, Hindmarsh (between Port Rd and Manton St). This will be the same format as last time - ie. minimum talk and maximum hands-on. There will be 1 or 2 sessions on the day. Once again we will be looking for volunteer helpers with a laptop or PC to load simple Basic programs into a PICAXE kit. This time we will offer a few more options such as a bigger chip and extra peripherals.

END OF AN ERA: For those with a long association with electronics and radio will be saddened to note that “Robbie’s” at Long St, Queenstown and a source of much second-hand and disposal electronics since about 1954 is closing for the last time soon. A few pictures to remind you of the shop are here.

MATHS PROBLEMS: There has been some discussion in the media lately and at the July meeting on the decline in mathematics in schools. Here are 2 maths problems from the UK “O levels” (about Aust. year 10). You be the judge. Extracts are from 1960 and 2006.

PAST EVENT REPORTS:

JULY 11 MEETING - FLIGHT SIMULATOR: On Friday July 11 Adam Webb demonstrated the free, open source Flight Gear flight simulator available in either a single CD for minimum operation or as a multiple set of DVDs to provide a complete simulation of the entire world together with an enormous selection of aircraft that includes fighter aircraft, commercial airliners, executive jets, aerobatic bi-planes, helicopters, hang gliders, paragliders, the Wright Brothers’ historic aircraft, you name it, in an ever-increasing list. Scenery includes most of the world’s cities, airports, roads, railways, landmarks, rivers, mountain ranges, islands, and oceans. This simulator comes as a “live”, bootable Linux disc so that no hard drive installation is needed.

Adam took us for flights in the Concord (no longer possible now in the actual aircraft, of course), in a light plane, and even Santa’s sleigh. We took off from the Adelaide Airport and flew up and down the gulf and around Kangaroo Island. We also took flights from Heathrow and around London, around Paris with fly-bys of the Eiffel Tower, Notre Dame and the Arc de Triumph, around New York including the Hudson River, Manhattan, Long Island and (we think) Martha’s Vineyard - all in one evening!

Flight Gear is an excellent demonstration of the application of maths and programming skills to very practical uses in flight simulation, navigation, and 3D graphics in the complex and disparate environment of present day computer hardware.

There were some distortion artifacts evident, especially when the scenery was close to the vantage point. The artifacts suggest that the there are limitations either in the software rendering engine that converts the scenery data to a picture or the video card and its drivers. The clue is that as the scenery moves the artifact area effected on the screen doesn’t. Then, if the view is down from a high altitude it looks quite accurate and starts to get stranger as the vantage point gets close to the scenery. The root cause of that can be in the practical limitations to the trig tables where a more accurate calculation would take too long if you use calculated trig values, or alternatively, if you use very long pre-calculated look-up tables, it takes up too much memory. The scenery data has to be limited as well so the less points and/or the fewer number of significant digits you have for each data point then the more evident the artifacts become. Those things should improve as time goes by. It will be very interesting to revisit this software in future.

JUNE MEETING - DDS: On Friday June 13 we had a discussion on Direct Digital Synthesis (DDS) that is planned as a project to be used as a very precise local oscillator in a digital radio (DRM) receiver, a transmitter, or an item of test equipment. (DRM transmissions start in Australia January 2009.)
The 2 methods of precision frequency generation over a range of frequencies in general use - PLL and DDS - were described.

Because crystal oscillators are so vital to almost all computers, precision electronic instruments, radio receivers/transmitters, mobile phones, GPSs, TVs, set top boxes, DVD, CD, MP3 players, electronic clocks and watches, then these were discussed in some detail. Terms like X, Y, AT, BT cuts, temperature stability, overtoning, twinning, grinding, etching, edge bevelling, flexure, shear, FT243, DC-11, K, mini-K, and series and parallel resonance were explained. Some circuits such as Colpitts, Hartley, Chow, etc were described. Some practical demos such as using a micrometer to determine a crystal’s frequency and a DDS device and its software were included.

MAY 9 MEETING - FUEL CELLS. At the May meeting David Tilbrooke, whose career as an industrial chemist embraced industrial process development, museum conservation, forensics and work with Artlabs, described the history, structure and chemistry of various chemical cells such as the Baghdad Battery (c.250BC), Leclanche, Clarke and Grove cells that eventually led to the discovery of fuel cells in the mid-1800s. The fuel cells David described rely on combining hydrogen and oxygen to produce electricity and water. The cells themselves consist of membranes, electrolytes and catalysts together with a continuous supply of hydrogen and oxygen. Once established, fuel cells continue to produce electricity as long as they are continuously supplied with hydrogen and oxygen which is the big advantage they have over primary and secondary cells. Some disadvantages of fuel cells are that some operate at very high temperatures, some use dangerous and often toxic chemicals, and some components are expensive such as platinum. Nevertheless, some cell types do look like being part of the solution to providing an alternative to our rapidly depleting fossil fuels for power generation and transportation - although an abundant supply of hydrogen has yet to be found.

David’s talk stimulated a lot of discussion, particularly relating to some side issues raised such as carbon dioxide geo-sequestration and his forensic work. Maybe we can get David to tell us about his forensic work at some future meeting.

APRIL 11 MEETING: Peter Reed explained the Capacitor Paradox that was raised at the February meeting and caused some controversy. The paradox is that it can be easily shown by experiment that if a charged capacitor is switched in parallel with an uncharged capacitor then the sum of the energy stored by the two capacitors is significantly less than was initially stored by the charged capacitor. Peter showed that the “lost” energy is not lost at all, but is dissipated as heat and electro-magnetic radiation (radio interference). He also showed that combining electronics with inductors in suitable switching circuits placed between the capacitors can almost completely eliminate any energy loss.

For more light reading on the Capacitor Paradox, Dr Pudney, Uni SA, has supplied some links:

http://www.hep.princeton.edu/~mcdonald/examples/twocaps.pdf

http://www.physicsforums.com/showthread.php?p=823340

There was also some discussion on a DDS VFO project that could be the basis of digital receivers when digital radio is launched on the AM, HF, and FM bands in Australia on January 1, 2009.

ELECTRIC CARS - TALK, DEMO. On Friday March 14 starting at 7:00pm at the WEA “Cottage” at 223 Angas St Adelaide, Dr Peter Pudney who has been heavily involved with the Darwin-Adelaide Solar Car Races since their beginning and more recently with “Trev”, Uni SA’s electric car, and to a lesser extent, an involvement with the recently launched Adelaide City Council’s electric bus, “Tindo”, will talk to us about these items. The talk will concentrate primarily on Trev. (Dr Pudney has spoken to us about Solar Cars previously.) A special feature of the evening will be a demo of an electric car using super-capacitor energy storage. Those of you at the last meeting will remember the spirited discussion on the “capacitor paradox” where the energy in a charged capacitor is used to charge another uncharged capacitor resulting in far less total energy afterwards. This apparent violation of the conservation of energy will most likely come up again in connection with energy storage in electric cars.

2008 MEETING PROGRAM: A number of members at our AGM suggested or volunteered to talk on a range of subjects during this year.

So far, we have: Fuel Cells (David T), VoIP PBX (Col H), Capacitor Paradox (Peter R), Virtualization (Andrew B), Heart Monitor (Eric P), Flight Gear flight simulator (Adam W), Turing Machine (David T), Aircraft Positioning System (Mark S to arrange). Many thanks to those who have volunteered. We would also like volunteers to have a look into Python, MIDI, Go, Making Live CDs, and Sim City (source code now available), or any other suitable subjects for possible inclusion in this year’s program.

Bar Camp 2008

Location:
Bridgewater Hall
Downstairs in the IT Share Workshop
Bridgewater Road
Bridgewater SA
There is a BBQ at the hall, so feel free to bring along food and drinks.

DECEMBER 7 MEETING: SHORT TALKS, INCLUDING PROJECT SUGGESTIONS.
For this meeting we tidied up a few loose ends, discussed some interesting items and introduced the game of Go. We also discussed the Postal Barcode, building “live” CDs especially using the PCLinuxOS command “mklivecd” to easily build customized live DVDs that are fully bootable backups, the “plane table” that Capt James Cook used for mapping much of the unknown world, and electric transport systems. Other items were held over for discussion during 2008.

NOVEMBER 9 MEETING: ADSL AT THE TELPHONE EXCHANGE END.
Tony Cormier’s talk on the installation of telephone exchange-end ADSL equipment, principally DSLAMs, and his Middle-East experiences were well presented together with plenty of photos and samples.The most obvious thing about installing ADSL in the telecommunications’ network, as Tony soon made us realize, is that it is very wiring intensive compared to anything before. The equipment itself is ever diminishing as the electronics gets smaller and more compact, so the effect is that we have buildings full of wiring and cables while at the same time the equipment occupies a lot less floor space - although the greater demand for power and the need for more air-conditioning does offset the reduction in floor space somewhat.

Presently the ADSL equipment is installed by removing the single jumper that connects the conventional switched voice call equipment from the cable side to the equipment side on the main frame and replacing it with two jumpers - one from cable to ADSL (the “c” jumper), and one jumper from ADSL to telephone equipment (the “x” jumper). On the other side of the ADSL equipment the internet data streams enter the Internet “cloud” via optical fibre.

In future, when the need for conventional voice calls disappears as expected within approximately the next 10 years, the “x” jumper will simply be removed along with the telephone equipment connected to it and we will have an “all IP” network.

The ADSL equipment is mostly located within existing telephone exchange buildings whether it belongs to Telstra or some other ISP. However, as customers continue to demand higher speeds there is a need to get closer to them over their copper wire so you will start to notice more and more roadside cabinets installations external to telephone exchanges.

Many thanks, Tony, for sharing your ADSL installation and your middle-East experiences with us. We now have a much better insight into the exchange-end of the ADSL network.

OCTOBER 12 MEETING - GROUP PROJECT DISCUSSION
The October 12 meeting was a discussion on possible SAMG group projects. Eric Patching demonstrated a heart beat monitor that could be a possible group project. Adam showed us a number of modules such as USB-to-serial, video motion detector, etc.

SEPTEMBER MEETING: . . . AND NOW A SEGUE TO A SEGWAY.
Geoffrey Bennett is a long time convenor of Linux SA and previous SAMG guest speaker on Linux (circa 1995) and the TiVo (December 6, 2002 TiVo Video Recorder ). This time he showed us and described his home-built version of the Segway (Open-Source Segway(R) - make sure you view the video!). The Segway is a compact personal means of transport. It is essentially a battery-powered, two-wheeled, motorized platform that the user stands on to ride. It relies on acceleration and gyroscope sensors combined with a lot of control electronics and very clever software to determine its stability and velocity. Geoffrey’s lecture/demo was well attended. His version of the Segway is a triumph of hardware and software design.

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