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Contents Vol.27, No.7; July 2014 SILICON CHIP www.siliconchip.com.au Features   14  Argo: Drones Of The Deep Oceans Thousands of drones are floating deep in the oceans of the world, monitoring temperatures and other data. They are fully autonomous and can change depth or rise to the surface to send data to satellites – by Dr David Maddison Threshold Voltage Switch – Page 26.   22  Review: AmScope Stereo Microscope Even people with 20/20 eyesight have difficulty soldering fine-pitch SMDs to PCBs. This stereo microscope is made for the task and it even has a camera eyepiece to record your work – by Andrew Levido   36  Eye-Fi Mobi SD Wireless Camera Cards Eye-Fi have gone mobile with their new range of “Mobi” camera SD cards. Now you can very easily send your pictures to any Android or iOS tablet or phone and share them with friends! – by Ross Tester Pro jects To Build   26  Threshold Voltage Switch This versatile unit switches a relay when an input voltage crosses a preset threshold. Use it to switch power to a fan, warning light or similar or use it to prevent a lead-acid battery from being over-charged – by John Clarke ASCII Video Terminal With VGA, Composite Video, USB Port & PS/2 Keyboard Input – Page 60.   60  Micromite, Pt.3: Build An ASCII Video Display Terminal It’s VT100-compatible and lets you add a video display, keyboard and USB to your next microcontroller project. It’s the perfect companion for microcontrollers with serial input/output such as the Micromite and PICAXE– by Geoff Graham   70  Touch-Screen Digital Audio Recorder, Pt.2 Second article gives the assembly details, provides some performance graphs and describes how it’s used – by Andrew Levido   80  L-o-o-o-n-g Gating Times For The 12-Digit Counter This module enables even higher resolution measurements with our 12-Digit Frequency/Period Counter. It adds a decade divider for the external timebase input to allow measurements using a gating time of 10,000s – by Jim Rowe Special Columns   40  Serviceman’s Log Oh goodie, a valve radio to fix – by Dave Thompson   57  Salvage It! Wrecking The Computer Itself Building The Touch-Screen Digital Audio Recorder – Page 70. Once you’ve pulled the main stuff out of your old PC, what do you do with the rest? Don’t bin it yet: there’s still lots of goodies waiting to be recycled – by Bruce Pierson  87 Circuit Notebook (1) Signal Injector & Tracer Uses TDA2822M Dual Power Amplifier; (2) Headlight Circuit For A 36V Electric Bike; (3) RS-232 Input For Non-Standard Signals; (4) Simple DIY Gizmos For SMD Desoldering   92  Vintage Radio The upmarket 1950 HMV R53A radiogram – by Rodney Champness Departments   2  Publisher’s Letter   4 Mailbag siliconchip.com.au  47 Subscriptions   48  Product Showcase   90  Online Shop  98 Ask Silicon Chip 103 Market Centre 104  Notes & Errata Long Gating Times For The 12-Digit High-Resolution Counter – Page 80. July 2014  1