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SILICON SILIC CHIP www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc. (Hons.) Technical Editor John Clarke, B.E.(Elec.) Technical Staff Ross Tester Jim Rowe, B.A., B.Sc Nicholas Vinen Photography Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Kevin Poulter Stan Swan Dave Thompson SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $105.00 per year in Australia. For overseas rates, see our website or the subscriptions page in this issue. Editorial office: Unit 1, 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. Fax (02) 9939 2648. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Recommended and maximum price only. 2  Silicon Chip Publisher’s Letter Head-up displays are a boon This issue features an article on head-up displays in cars, starting on page 14. For a month or so now, I have been driving with a head-up display projected on to the windscreen, just below my normal view of the road ahead. Surprisingly, there is nothing particularly high-tech about the display itself. It is basically a 3-digit 7-segment multi­plexed display which projects up onto a reflective layer on the windscreen. The display is actually mirrored vertically so that the image can be read. I have reviewed two forms of the head-up display. The first is based on a GPS receiver (the same as in any GPS satellite navigation system) which simply displays the true vehicle speed. As such it has two significant advantages compared with my Honda Accord’s own speedo: it is far more accurate and I don’t have to glance down at the speedo to check it; I just slightly shift my gaze down a little, with my eyes never leaving the road ahead. It is such an effective system I have virtually stopped checking the speedo itself. But there are drawbacks with the GPS head-up speedo display. Like all GPS units, it takes a while, maybe several minutes, before it first accesses the satellites and gives a meaningful reading. Second, it does not work in tunnels or in some inner city streets where tall buildings block the satellite signals. Which is why I tried the second form of head-up display, based on signals from the car’s OBD (on-board diagnostics) socket. This has a number of advantages over the GPS approach. First, it does not have a significant delay before it starts working and it is unaffected by tunnels, tall buildings or whatever. It is not quite as accurate as the GPS display but is considerably closer to the actual speed than the Honda’s own speedo. The OBD head-up display also shows a lot more information. As well as speed, it has a dramatic-looking bargraph tachometer and a smaller 2 or 3-digit display of the instantaneous fuel consumption in litres/100km. This really is a boon because it gives instant feedback about fuel consumption for even the slightest deflection of the accelerator pedal. Even more valuable, it tells you when your fuel consumption is zero! In my Honda Accord, this occurs at any speed above about 57km/h when my foot is off the accelerator and the transmission is in Drive. This makes it far easier to drive with the utmost fuel economy in mind. It becomes something of a game – you try to use the minimum throttle setting at all times while keeping up with the traffic. At the same time, you develop the strategy of braking as little and as late as possible, driving very smoothly, anticipating changes of lights and traffic movements far ahead. All of this is necessary if you are to achieve excellent fuel consumption. Now I know that most motorists don’t drive with fuel economy in mind, even though fuel is expensive and ever rising in cost. If queried about this behaviour, they would no doubt argue, correctly as it happens, that fuel is not a major cost in typical car ownership. For my part, it is part of my normal driving behaviour to drive as economically as possible. I also happen to think that my passengers enjoy a very smooth trip better than one characterised by jack-rabbit starts, frequent braking and so on. For anyone who is of like mind therefore, a head-up display with actual speed and instantaneous fuel consumption is most useful. And the great thing is that you don’t have to change your car to get one. They can be purchased cheaply and they are simple to fit. Furthermore, if you drive long distances, driving with economy in mind can save a substantial amount in fuel cost over a year, as well as considerably reducing wear and tear on tyres, brakes, transmission and so on. Leo Simpson siliconchip.com.au