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skin if touched and while the coil is not as hot, it is still quite warm. I realise that the average DC current will be greater now (about twice) and that the unit is current limited. I am still concerned about the long term effects of the high temperatures, particularly on the resistor. Any comments? (B. S., Canberra, ACT). • Any high power wirewound resistor will run at very high surface temperatures when running at more than 50% of its rated power. You could always reduce the current limit figure somewhat and also ensure that airflow around the coil and ballast resis­tor is as unrestricted as possible. Connecting the theremin to a guitar amplifier I just purchased a Theremin kit (described in the August 2000 issue) and was wondering if I could replace the line out from an AV type plug to one that could plug into a guitar amp? (L. J., via email). • Yes, you can connect the There­min to a guitar amplifier but you will need to reduce the signal level. Connect a 10kΩ resistor in series with the 10µF output capacitor and replace the existing 10kΩ resistor at the output with a value of 1kΩ. This will reduce the Theremin’s output from a nominal 500mV to 50mV. Running two tubes with the fluoro inverter I intend to purchase a kit for the high efficiency fluores­cent inverter from Altronics but I have a question about it. Will this kit run two 20W tubes in parallel? (J. H., via email). • In existing form, the inverter will not drive two tubes in parallel because once the first tube ignites, there will be insufficient voltage to ignite the second. The only way to do it would be to have a common 340V supply and then build separate driver circuits (involving transformer T2 and Mos­ fets Q3 & Q4) for each tube. The easiest way to do that would probably be to purchase an extra PC board (from RCS Radio) and use the driver end of the second board to power the second tube. BOOK REVIEWS – continued from page 89 headings. In the introductory section there are chapters on robot basics, tools and supplies, buying parts, common electronic components, electronic construction techniques and fundamentals of programming. Section 2 has chapters on building robot platforms out of plastic, metal and wood, LEGO-based robots and LEGO Mindstorms RCX. Section 3 is entitled “Power, Motors and Locomotion” and has chapters on batteries, DC motors, steppers and servos. Section 4 has practical robot pro- jects including a 6-legged walking robot and a few robot arms. Incidentally, how the book comes to be subtitled with “99 inexpensive robotics pro­ jects” is a mystery; there are only a few complete robots described. Section 5 is entitled “Computers and Electronic Control” and has chapters on interfacing computer and Microcontrollers, using the Basic STAMP, the BasicX and OOPic microcontrollers and remote control systems. Finally, Section 6 is on “Sensors and Navigation” and has chapters on Notes & Errata LP Doctor, January 2001: the specified fuse is wrong. It should be 150mA slow-blow. PIC Programmer and Checker­board, March 2001: the text on page 69 (third column) refers to jumper J2 and switches SW3 and SW4. These should be JP2, S11 and S12, respectively. The circuit diagram and overlay are correct. On the PC board, there is insufficient space to fit the 2200µF 25V filter capacitor but a value of 1000µF 25VW will be adequate. Also the 10kΩ pullup resistor for RA4 on the LCD adapter is not low enough to give reliable operation. Use a value of 4.7kΩ instead. Bass Blazer, February 2001: some filter PC boards (code 01102011) may not have a connection between pin 4 of IC6 and V+. This connection provides power to IC6. If your PC board has this error, use a short length of fine insulated hook-up wire to connect IC6 pin 4 to the cathode end of D9. The relevant PC artwork on our website has been corrected. sense of touch, collision avoidance and detection, fire detection, sound input and output, tilt and gravity sensors. In summary, this is a pretty useful book although, as mentioned above, you need to have reasonable electronics and related mechanical skills to get the best out of it. It also has a good list of web sites for further research. Our copy came direct from the publisher. (L.D.S.) Note: the above books are available through major retailers such as Jaycar, Dick Smith Electronics, Altronics and from the Technical Bookshop, Melbourne and other major book retailers. 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. April 2001  93