Fullscreen HTML5Med Res (??MB)HTML4

1997) to check that you have not soldered two pads together. We are not aware that the pinouts for the large 7-segment displays are any different to the ones we used in the prototype. These pinouts follow an industry standard. The exact frequency of operation for a crystal oscillator cannot reliably be tested with a probe and frequency meter. This is because the probe’s capacitance can load the crystal and slow down its frequency. Normally, if you want to reliably measure the frequency of a crystal oscillator, you must do it via a buffer stage. A suitable crystal can be obtained from Farnell Electronics, phone 1300 361 005. Their catalog number for the crystal is 569-914. Sync output for TV pattern generator I would like to know if the Colour TV Pattern Generator described in June & July 1997 has or can have a separate sync output as well as the composite video. I have an application that requires this. (D. P., -via email). • The composite sync signal is available at pin 16 of IC10. Since its amplitude is 5V peak-to-peak, you may need to attenuate it to the required level for your application. Notes & Errata Daytime Running Lights for Cars, August 1999: a modification to allow the circuit to be used with cars having headlight switching in the negative line is published in Circuit Notebook this month. PC Monitor Checker, August 1999: circuit modifications to give more ideal scan frequencies are published in Circuit Notebook this month. Mailbag: continued from page 44 charged at about 5A by two 42W Solarex panels. These are now nearing 30 years old but the batteries have been replaced. All lights in the home are fluoresents modified to run from 12VDC. My amateur station (VK4KAL) is operated from batteries, direct where possible or by DC/DC converters. A 1500W inverter is on standby, although rarely used. The 486 DX2/66 computer I am using is also running from 12V DC. We are now connected to the grid but only for the deep freezer and washing machine (not an automatic – these are water wasters in our dry area). The welder has to be AC-operated although the frame of our home was welded using battery power – 36VDC (we live in white ant country!). We use gas for cooking and our hot water is solar-heated. Where possible, every gadget we use is 12VDC operated. We don’t have blackouts, although recently the system in our area was out for three days due to 3km of mains being blown down in a freak storm; but our lights were on. For what it is worth, invest in a smallish Solarex panel and a 12V deep cycle battery. I run as a “emergency” an 18W panel charging a deep cycle marine battery to “fire up” an FT 747GX which draws 20A on transmit. This also lights my “shack” if ever needs be. A couple of amateurs living in Brisbane have similar small setups running 12V fluoros because of blackouts. Don’t use inverters unless absolutely necessary. They waste power while idling. I throw DC plugpacks in the rubbish bin. Why shouldn’t I, with 3kW of DC power at my disposal? We have the best of both worlds. A. Loveday, Rubyvale, Qld. DC concept is worthwhile I have just read your “Publisher’s Letter” for October 1999. I must say that you have touched on a point that I have been trying to make for quite some time, much to the amusement of my friends and colleagues. I believe that there is little to be gained by having domestic dwellings on the 240VAC mains. Apart from heating, all appliances could be powered by low voltage DC, be it 12, 24 or 32 volts. Heating, and by this I mean cooking, space heating and hot water systems, can be more efficiently be handled by gas. There are quite a few domestic appliances (eg, TVs, videos, etc) that are dual voltage and cooling is not a problem with 12VDC fans, made for large trucks, on the market. Refrigeration could also be run from 12VDC because of the relatively new 12V compressors available and of course, the large 12V absorption refrigerators have been around for a while. Air conditioning can again be via 12V compressor or evaporative, as can all manner of power tools. Even audio amplifiers can be low voltage powered; those massive “thumper” systems in cars are testimony to that. You did mention some of these in your article and my knee-jerk reaction was “now someone will listen to me!” I could go on and on about this subject but I had better stop now and say thank you for a timely article. The amusement mentioned above? I am a qualified electrician! Maybe a traitor to my trade? J. Smith, Middleton, SA. 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 Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. November 1999  93