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Contents Vol.15, No.6; June 2002 www.siliconchip.com.au FEATURES 8 Helios: The Solar-Powered Plane Last year, it set a new altitude record for winged aircraft. This month, it has its first commercial trials. Its fuel? . . . sunlight! – by Bob Young Lock Out The Bad Guys with A Fire­wall – Page 16. 80 Fuel Cells Explode! Well, they don’t literally explode but their numbers and types sure are. Here’s all you need to know in this sequel to last month’s article – by Gerry Nolan PROJECTS TO BUILD 28 Remote Volume Control For Stereo Amplifiers You can add a remote motorised volume control to just about any stereo amplifier. Here’s how to do it – by John Clarke 54 The “Matchless” Metal Locator It’s cheap, it’s easy to build and it could find a fortune – by Thomas Scarborough Remote Volume Control For Stereo Amplifiers – Page 28. 62 Compact 0-80A Automotive Ammeter The latest addition to our line-up of PIC-based automotive projects. Build it and keep tabs on your car’s electrical system – by John Clarke 72 Constant High-Current Source A companion project to last month’s stepper motor controller, this simple high-current source can also charge batteries – by Ross Tester “Matchless” Metal Locator – Page 44. COMPUTERS 16 Lock Out The Bad Guys With A Firewall Don’t get hacked while you’re on the net. Here’s three free firewalls to keep the cyber vandals out – by Greg Swain SPECIAL COLUMNS 38 Serviceman’s Log This little “telly” came to town – by the TV Serviceman 76 Vintage Radio The 1935 Tasma M290 console – by Rodney Champness DEPARTMENTS 2 4 35 42 53 Publisher’s Letter Mailbag Circuit Notebook Product Showcase Subscriptions Form www.siliconchip.com.au 61 87 89 94 96 Silicon Chip Weblink Ask Silicon Chip Notes & Errata Market Centre Advertising Index Compact 0-80A Automotive Ammeter – Page 62. June 2002  1