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Advertising Index Agilent Technology....................... 15 Altronics.................................. 88-91 Bitscope....................................... 77 Dyne Industries.............................. 9 Electronex...................................... 7 Element14.................................... 14 Embedded Logic Solutions.......... 12 Emona Instruments...................... 65 Front Panel Express..................... 11 Geoff Coppa............................... 111 Grantronics................................. 111 Ask SILICON CHIP DOWNLOAD OUR CATALOG at . . . continued from p110 www.iinet.net.au/~worcom the performance at high frequencies is limited by the PCB layout which, while excellent, doesn’t give total cancellation of electromagnetic radiation. So it would require an extensive redesign and a lot of experimentation to make it much better (if we even could). Having said all that, we don’t think it would hurt to add a 10pF capacitor across the compensation network. Reverse switch for 5-inch locomotive I am going to use the 12V 10A Speed Controller (SILICON CHIP, June 1997) in a 5-inch gauge electric locomotive and was wondering if it was possible to incorporate a reverse switch in the Using Two PC Power Supplies for 24V (Circuit Notebook, August 2012): most PC power supplies have their output ground internally connected to earth. For this circuit to work, one sup112  Silicon Chip High Profile Communications..... 111 WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au Instant PCBs.............................. 111 circuit? My concern is with diode D2 and capacitor C3 across the motor terminals. Would I put the reversing switch before or after the diode and capacitor? I intend to use a double pole/ double throw switch for the reverse. (J. A., via email). • Place the reversing switch between the controller and the motor. The diode should be on the controller side, while the capacitor should be directly across the motor. Make sure the motor is stopped before changing the reverse SC switch position. LED Sales.................................. 111 Notes & Errata Wideband Oxygen Controller Mk2 (June-August 2012): on the PCB, the anode of ZD1 does not connect to the adjacent ground track as it should. The PDF file on the website has been corrected to fix this. If you bought a PCB from the first batch, bend the lead of ZD1 over and solder it to the negative (lower) pad of the adjacent 10uF capacitor or fit a wire link between these two pads. Ensure it can not come in contact with any other nearby pads. Hare & Forbes.......................... OBC ply must have floating outputs. The low-voltage ground is normally earthed through one or more solder pads under the screw heads holding the internal PCB to the earthed metal case. Typically, the supply will still operate if these earth connections are broken (eg, by using insulating washers under the screw heads). Do NOT disconnect the mains earth at the input socket as the metal housing must remain earthed, as should any EMI suppression components. Care must also be taken if a PC power supply is opened up as they contain large, high-voltage capacitors which can retain a lethal charge for some time and they often have exposed mains and high-voltage DC components. Jaycar .............................. IFC,53-60 Keith Rippon............................... 111 Kitstop........................................ 109 LHP.NET.AU............................... IBC Low Energy Developments........ 111 Matrix Multimedia......................... 10 Microchip Technology................... 39 Mikroelektronika........................... 69 Mouser Electronics......................... 5 Oatley Electronics........................ 97 Ocean Controls.......................... 101 ozQRP........................................ 111 Quest Electronics....................... 111 Radio, TV & Hobbies DVD..... 87,109 Red Button Technologies............. 21 RF Modules................................ 112 Rohde & Schwarz........................ 13 Sesame Electronics................... 111 Silicon Chip Binders.............. 51,111 Silicon Chip Bookshop............... 103 Silicon Chip Order Form............. 105 Silicon Chip Partshop................. 104 Silicon Chip Subscriptions........... 81 Siomar Battery Engineering.... 3,111 Soltronico..................................... 11 Splat Controls............................. 111 Tekmark Australia......................... 14 Trio Smartcal................................ 13 Truscotts Electronic World.......... 111 Wiltronics........................................ 8 Worldwide Elect. Components... 112 siliconchip.com.au