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box sides. This gives the operator the ability to adjust the inertia and braking to suit his own requirements. Unfortunately, both units failed to operate. The test supply is from an old Triang Controller claiming to be 15VAC but on testing is 17VAC. The unit was connected to this supply but not connected to the track. Our know­ ledge of electronics then limits us from checking much further. I know that on the output side of the bridge rectifier the voltage is DC and the output is 1.414 times the input. This makes the feed to the circuit approx­imately 24VDC. This checks out as correct. Both our units have been assembled on Veroboard. These have been carefully checked numerous times to ensure that no error exists in the circuit. Our questions are as follows: (1). Could the input VAC be too high, thus damaging some of the components? (2). A silly thought, but was an error discovered after the article was published and rectified in a later issue of the magazine? (No insult intended!) (3). Nobody can tell us the handling capacity of the Veroboard strips; ie, can one strip carry 3A? (4). Is it acceptable to change the trimpots as mentioned above? (M. B., Logan City, Qld). • The most likely reason for the malfunction in your train controller circuits is mistakes in the Veroboard layouts. From bitter experience we know how easy it is to make mistakes. Your best approach is to obtain the PC board as it is much easier to assemble. You can purchase it from RCS Radio Pty Ltd, 41 Arlewis Street, Chester Hill, NSW 2162; phone (02) 9738 0330. The board is type number 02102931 and is $12.65 plus $3.30 for postage and packing. You can change the trimpots to pots, as you have done. Basic Stamp2 Xout function I have been doing some programming on the Basic Stamp2 module and am interested in using the Xout function. This provides remote control functions via the reticulated mains power lines within a building. Special 110V interface modules are available in USA for this purpose. Is this facility available for the Australian 240VAC power system? Are there approved “control via mains” systems in use here and if so, are the interface units available Coil failure in ignition system I have built the High Energy Ignition system as described in the June 1998 issue and the unit has worked well. But the other day my ignition coil failed and I think this caused the output transistor to fail as well. I checked for continuity from the transistor’s heatsink to case and there was a short (it was still connected up to my car, with power off when I checked it). I can find no reference to this transistor in either the Dick Smith Electronics or Jaycar catalog. Is there a higher-rated substitute I can put in? By the way, is there a simple go/nogo test for the output transistor? I think it was a Darlington type. (M. K., via email). • The coil probably failed because the transistor’s collector became short circuited to the case. This would have meant that the full battery voltage was connected across the coil which would burn it out fairly quickly. This short from the transistor to case for purchase? (K. M., via email). • We referred your question to Microzed Computes, the Austra­lian agents for The Basic Stamp2. Their answer is as follows: Our understanding is that X10 is being discouraged in Aus­tralia by power supply authorities because of developments in power line accessing of meter readings, using a protocol that would collide with X10. A more reliable option is CE BUS from Clipsal. This uses a separate 2-wire, low tension bidirectional bus. CE Bus has more features and should interface with the Stamp. would suggest that it is the insulating washer between the transistor and case or the bush which has failed. Check that there are no sharp edges around the mounting hole for the transistor as this will give a starting point for any arc-over between the transistor and case. Use either a new silicone washer or two mica washers. You can check the output transistor (it is a Darlington type, by the way) by using your multimeter to measure the resist­ance between base and emitter, between base and collector and collector to emitter. The 1999/2000 Dick Smith Electronics cata­log shows how it is done on page 236. Notes & Errata Opto-Electronic Ignition, October 2000: the circuit fea­tured in Circuit Notebook on page 58 shows a 470Ω resistor con­nected to the collector of Q2 via a .01µF capacitor. This resis­tor SC should be 470kΩ. 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 2000  93