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Notes & Errata Loudspeaker Protector, October 2011 & Universal Loudspeaker Protector, November 2015: both articles refer to a 70°C thermal cut-out from Jaycar, Cat. ST3831. This is incorrect, the correct catalog number is ST3833. High-Visibility 6-Digit LED GPS Clock, December 2015-January 2016: two bugs have been identified in the firmware. One causes the unit to display the incorrect time for 8pm and later when set to 12-hour mode. The other causes minutes to be shown as 60 rather than 00 for one minute if the current time zone has an offset that is not a whole number of hours. Firmware v1.2 (revision C) fixes both problems and is available for download from our website. Affected users can send their PIC32 chips back in to be re-programmed if they are unable to do so themselves. In addition, in Pt.2, the instruc- Ask SILICON CHIP . . . continued from page 94 minimal heat in the 10Ω resistors. A higher frequency could reduce saturation time in the windings. USB power injector for STB HDD The USB Power Injector featured in the January 2016 issue has caught my interest. I am wondering if this simple circuit would be suitable for use in powering an external HDD (up to 500GB) for a Dick Smith (DSE) Set Top Advertising Index tions for gluing the case together state “The front panel is rotationally symmetrical so its orientation is not important . . .”. While the front panel is rotationally symmetrical, it does not have mirror symmetry so it is possible to glue it “flipped” such that the LED colons will slant in the wrong direction. Please pay attention to this possibility while assembling the case. Allan Warren Electronics.............. 95 QuickBrake, January 2016: The voltage applied to the reset pin of 7555 timer IC3 once the timing capacitor has charged may not reach a sufficient level to release the reset. To solve this, change the 220kΩ resistor between pin 4 of IC3 and the 5V supply to 82kΩ. In addition, trimpot VR1 is shown incorrectly orientated in the circuit diagram (Fig.1). Clockwise rotation reduces the resistance and thus reduces sensitivity, as stated in the text. Jaycar .............................. IFC,45-52 Box [DSE codes “GH5930” & “GH5944” – I have one of each and my Dad has two of the earlier model (the GH5930)]. According to the manuals, it would appear that both of these units may be able to handle a USB drive of “up to” 500GB (the GH5944 up to 2TB) with a supplementary power supply and, if necessary, reformatted to FAT32. Would you agree with this proposition? (P. M., via email). • Yes, the USB power injector should be suitable for the external hard drive. Power capability is dependent on the 5V supply so it needs to be rated for SC the hard drive’s current drain. Altronics..................................... IBC Digi-Key Electronics....................... 3 DSCAPE...................................... 95 Emona Instruments...................... 25 Front Panel Express..................... 11 Hammond Manufacturing............. 10 Hare & Forbes.......................... OBC Icom Australia................................ 9 Keith Rippon Kt Assembly ........... 95 LD Electronics.............................. 95 LEDsales...................................... 95 Master Instruments...................... 95 Microchip Technology................... 21 Ocean Controls.............................. 6 PCBCART...................................... 5 Sesame Electronics..................... 95 SC Radio & Hobbies DVD............ 70 Silicon Chip Binders..................... 66 Silicon Chip Online Shop........ 88-89 Silicon Chip Subscriptions........... 87 Silicon Chip Wallchart.................. 93 Silvertone Electronics.................. 13 Tronixlabs.................................. 7,95 Next Issue The April 2016 issue of SILICON CHIP is due on sale in newsagents by Thursday 24th March. Expect postal delivery of subscription copies in Australia between March 24th and April 8th. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. 96  Silicon Chip siliconchip.com.au