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Contents Vol.31, No.12; December 2018 Features & Reviews 12 “The Grand Tour”: the incredible Voyager missions Way back in 1977, two Voyager spacecraft were launched to probe Saturn, Uranus, and Neptune. 41 years later – and way past their expected demise – they’re now the most distant man-made objects in space – by Dr David Maddison 44 The Arduino Uno’s cousins: the Nano and Mega Arguably the world’s most popular micro (especially amongst hobbyists), the Arduino has two not-so-well-known variants, the smaller Nano and the larger Mega 2560. Here’s an explanation of the differences – by Jim Rowe 74 El cheapo modules, part 21: stamp-sized audio player SILICON CHIP www.siliconchip.com.au No-one would have believed that the two Voyager spacecraft would still be operational 41 years later. But they are, albeit running on limited power – Page 12 You won’t believe how sensitive this new Magnetometer is. We found it could detect a pin head centimetres deep! – Page 24 Less than five dollars gets you the DFPlayer mini: a tiny (21 x 21 x 12mm) digital audio player which can handle MP3, WMA and WAV, in mono or stereo, off either a microSD card or USB flash drive with a capacity up to 32GB – by Jim Rowe Constructional Projects 24 An incredibly sensitive Magnetometer to build A magnetometer detects changes in magnetic fields, whether natural or manmade. This magnetometer is SO sensitive you have to make allowances for such things as waves and tidal flow! – by Rev Thomas Scarborough 38 Amazing light display from our LED Christmas tree . . . Last month we brought you our EXPANDABLE Christmas Tree, which is already very popular with readers (judging by the number of kits sold!). Now we present a controller to provide spectacular display options – by Tim Blythman 66 A Useless Box What does a Useless Box do? Well, not much – it’s pretty useless! But build this nonsense project and you’ll keep the kids (and grandkids) amused until at least next Christmas – and probably way beyond – by Les Kerr & Ross Tester 84 Low voltage DC Motor and Pump Controller (Part 2) With a huge array of options to suit YOUR particular application, this motor/pump controller will handle up to 40A DC on a nominal 12V supply. We couldn’t fit it in last month – so we’ve used the time to include even more! – by Nicholas Vinen Your Favourite Columns 58 Serviceman’s Log Travelling makes me go cuckoo! – by Dave Thompson 78 Circuit Notebook (1) Simple guitar practice amp (2) Accurately measuring voltage and current at the same time (3) 1kHz crystal-locked sinewave oscillator 94 Vintage Radio 1948 AWA compact portable Model 450P – by Graham Parslow Everything Else! 2 Editorial Viewpoint    99 4 Mailbag – Your Feedback    103 64 Christmas Showcase    104 siliconchip.com.au 82 SILICON CHIP Online Shop   104 Ask SILICON CHIP Market Centre Advertising Index Notes and Errata Want to be able to individually address each LED in our expanding Christmas Tree? We show you how to do it with this new controller – Page 38 They can’t resist flicking the switch. But when they do, Froggy comes out and turns the switch back off again! Build it for Christmas! – Page 66 This month’s El Cheapo module is intriguing: a digital audio player, complete with its own amplifier and card reader, for less than $5 out of China! – Page 74 www.facebook.com/siliconchipmagazine