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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP FOR SALE PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au SOLAR PANELS LOW COST: full range 5W to 250W, eg: 40W/12V Poly $69, 130W/12V $169, 190W/24V $165, 200W/12V $225, 250W/24V $225, 230W Poly $190. AGM Batteries: 7AH $19.50, 9AH $24.50, 20AH $52.50, 55AH $129, 105AH $199, 220AH $399. (03) 94705851 or (03) 9478 0080 chris<at>lowenergydevelopments.com.au www.lowenergydevelopments.com.au 544 High St, Preston 3072, Melbourne. PCBs & Micros: Silicon Chip Pub­ lications can supply PCBs and programmed micros for all recent (and some not so recent) projects. Order online or phone (02) 9939 3295. LEDs! Nichia, Cree and other brand name LEDs at excellent prices. LED drivers, including ultra-reliable linear driver options. Many other interesting and hard-to-find electronic items! www.ledsales.com.au Audio + Video: Professional quality Quest AV brand equipment is made and sold in Australia exclusively by Quest Electronics. Ph 0431 920 667. sales<at>questronix.com.au PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au KIT ASSEMBLY & REPAIR KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years experi- NIXIE CLOCK KITS SILICON CHIP July-Aug 2007 Full kits & spare tubes still available (For a limited time only) Phone 0403 055 374; Email glesstron<at>msn.com Television Replacements Your one-stop shop for all your electronic parts from aerials to zener diodes. 134a Ayr Street, Doncaster 3108 03 9850 4144 sales<at>tvr.com.au For Capacitors, Transistors & Integrated Circuits Call or email for details For our specials, like us on Facebook. ence and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $10 inspection fee plus charges for parts and labour as required. Labour fees $35 p/h. Pensioner discounts available on application. Contact Alan on 0425 122 415 or email bigalradioshack<at> gmail.com ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words plus 95 cents for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. and what’s more, it has a small drain and consequently the battery slowly discharges when the van is not in use. So it seemed reasonable to increase the output of this power supply and connect it in parallel with the solar panel input (120W) to the MPPT, using a Mosfet as a protection diode in the power supply’s output. I guessed at setting the power supply output to 17V since this is just below what the panel would produce when charging via the MPPT. It was not my intention to have both power supply and panel charging simultaneously although it will depend on the software as to siliconchip.com.au whether this will be OK. In fact, the input to the MPPT from the panels is 15.8V during bulkcharging and this seems to charge the battery more quickly than using the power supply. The results were interesting. Using the power supply, the MPPT Controller went into bulk charging mode as expected but the bulk charging LED flashed off briefly about every four seconds. In the description, it says that if the battery voltage is lower than 10.5V, the MPPT will charge in bursts with the LED flashing every four seconds before bulk charging begins. By this I presume that flashing means it is on briefly every four seconds but in this case, it is off briefly every four seconds. In fact, the battery voltage was around 12V so perhaps this is a coincidence. So is my arrangement to have the power supply charge the battery via the MPPT Controller reasonable? What could be the reason for the brief flash off every four seconds until bulk charging ends ? (D. W., via email). •  The MPPT Charger assumes that a solar panel is connected rather than a power supply. If using a power supply instead of a solar panel, it would be continued on page 112 March 2014  111 Advertising Index Ask SILICON CHIP . . . continued from page 111 best to use a current-limited supply set for around 6.6A and at 18V. That is because the MPPT charging works on the fact that the current will drop as the solar panel is loaded. The solar panel output follows the VI curve as shown in Fig.1 of the February 2011 issue. The flashing of the LED during bulk charging indicates the way the MPPT system works. This system periodically checks the panel to set the circuit up for maximum power transfer. The LED indicates when this is happening. Queries on the Jacob’s Ladder My son and I are looking at building the Jacob’s Ladder Mk3 (SILICON CHIP, February 2013) project together and among other things, learning how it works. I have a few questions as this is our first foray into high-voltage electronics. What is the minimum safe distance from the electrodes that one can safely enjoy the arc without a decent acrylic tube barrier? While the project recommends a car battery, after a scan over the circuit diagram, could the project be run from a 12V 5A (or better) DC power supply? And how long can the ladder be in operation before it overheats, if it overheats? (A. F., via email). •  The spark voltage will jump across a 30mm gap. If the gap is made too large, the spark will simply jump across the terminals of the coil itself. However, you should avoid putting your hands or any other body part within about 10cm of the spark wires, merely to avoid the possibility that you might inadvertently go too close and 112  Silicon Chip DOWNLOAD OUR CATALOG at www.iinet.net.au/~worcom WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305  Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au come into contact. If you do that, you won’t do it again! A power supply capable of more than 5A would be needed; preferably 8-10A. The unit should not overheat, even if it is used continuously. After all, this unit is merely a variant of our ignition system which is intended for continuous use in the engine bay of a vehicle. Super Jacob’s Ladder with two transformers I would like to connect the outputs of a 15kV neon transformer to the output of a 10kV oil fire transformer to produce a 25kV Jacob’s Ladder. Would this be OK or would I need high-voltage diodes to stop feed from one transformer getting into the other transformer? If so, what diodes would I need? At the moment I have two Jacob’s Ladders but would like to boost it up if possible. (A. F., via email). •  You can connect the two secondary windings of your transformers together to get a theoretical total of 25kV. However, you must do it so that the voltages add instead of subtract (there the result would be only 5kV). In effect, you have it connect the start of one secondary winding to the finish of the other. Since there is probably no easy way of identifying the starts and finishes, you would have to do it by trial and error. If you get it right, the total voltage will jump a Altronics.................................. 80-83 Core Electronics............................. 8 Emona Instruments...................... 38 Freetronics................................... 10 Gless Audio................................ 111 Hammond Manufacturing............. 77 Hare & Forbes............................. 2-3 Icom Australia................................ 7 Jaycar .............................. IFC,51-62 Keith Rippon .............................. 111 KitStop.......................................... 79 LD Electronics............................ 111 LED Sales.................................. 111 Low Energy Developments........ 111 Master Instruments........................ 5 Microchip Technology............... OBC Mikroelektronika......................... IBC Ocean Controls............................ 49 QualiEco Circuits Pty Ltd............. 50 Quest Electronics....................... 111 Radio, TV & Hobbies DVD............ 79 RF Modules................................ 112 Sesame Electronics................... 111 Silicon Chip Binders................... 102 Silicon Chip Bookshop................. 95 Silicon Chip Online Shop.... 104-105 Silicon Chip Subscriptions........... 25 Television Replacements........... 111 Tekmark Australia........................... 9 Tenrod Pty Ltd.............................. 17 Virtins Technology........................ 11 Wiltronics...................................... 41 Worldwide Elect. Components... 112 much bigger spark gap than it otherwise would. However, you should remember that the maximum output voltage you actually obtain will depend on the dimensions of the spark gap in the ladder and the insulation of all the wiring leading from the transformers to the Ladder itself. Even so, the resulting Jacob’s Ladder display will be limited by the less powerful transformer. In practice, the display might not be any better than that produced by the high-energy ignition coil we employed in the Jacob’s Ladder featured in the February 2013 issue. And since it is battery-powered, we think it would be safer than your SC transformer-powered version. siliconchip.com.au