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Contents Vol.33, No.3 March 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 14 The Arduino: a retrospective The Arduino has only been around for 15 years but it has a huge devoted (and growing) following world-wide. We look at its origins (did you know it was named after Italy’s first king?), where it is now and where it’s going – by Tim Blythman 38 Geographic Information Systems & Digital Cartography We all use digital maps just about every day (think GPS). But how are those maps produced and kept up to date? And what are Geographic Information Systems all about? You may be helping as you drive/walk/bike around – by Dr David Maddison 61 What to do when you bend (OR Break!) your Arduino Whoopsies do happen (ummm – do we speak from experience?). The Arduino is pretty cheap but wouldn’t you rather repair it than buy a new one? Here are some hints and tips we’ve uncovered over the last few years – by Tim Blythman The Arduino has come a long, long way in just 15 years. With all its variants it’s arguably the world’s favourite micro platform – Page 14 “True Valve Sound” from our new Guitar Overdrive and Distortion Pedal, because it uses a true valve – Page 24 Constructional Projects 24 “True valve sound” Guitar Overdrive & Distortion Pedal You get true valve sound because it uses a true valve – the Korg Nutube 6P1 dual triode. But this new valve operates from very low voltage – even a battery – so this is a perfect (and safe) project for budding young axemen – by John Clarke 74 Programmable Temperature Control with a Peltier Need stable temperature – say for hatching chickens, brewing beer, cooling that same beer, or a host of other processes? Set temperatures from near freezing up to 70° or so and hold them there with this Peltier Controller – by Tim Blythman 90 1000:1 AC High Tension Ignition System Probe We barely give them a second thought these days but those digital maps must have come from somewhere! – Page 38 It’s surprisingly tough to measure the actual output voltage of an automotive (or aircraft/boat) ignition system when they can easily exceed 50kV. If you work with ignition systems, you’ll want to build this high tension probe – by Dr Hugo Holden 96 Building Subwoofers for our new “Bookshelf” Speakers We’ve finished off the bookshelf speakers – so why not complement them with these easy-to-build subwoofers? Normally you’d only need one but if you build two, you also have a couple of very handy stands – by Phil Prosser Your Favourite Columns 50 Circuit Notebook (1) Low-noise split supply and switched gain signal amplifier (2) Combining DDS and IF Alignment circuits (3) Resurrecting a turntable with a Micromite Explore 64 68 Serviceman’s Log The vacuum cleaner that didn’t suck – by Dave Thompson 101 Vintage Radio Toshiba 7TH-425 Wall Radio – by Ian Batty Everything Else   4   6   89 107 Editorial Viewpoint Mailbag – Your Feedback SILICON CHIP ONLINE SHOP Ask SILICON CHIP 111 Market Centre 112 Advertising Index 112 Notes and Errata Our Peltier Controller will hold a constant temperature in a huge variety of applications – Page 74 Modern ignition systems can develop way over 60kV making them very difficult to measure. If you work with ignition systems you need this new 1000:1 AC Ignition System Probe – Page 90 Just about anyone – even you! – can put these high performing bookshelf speakers together! – Page 96 www.facebook.com/siliconchipmagazine