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Boosting the 5A speed control I recently completed the AC Motor Speed Controller from the October 2002 issue. However, I need to use it with an 1850W router. Can the circuit be modified to handle this amount of power? (A. H., via email). • The two main factors setting the maximum current are the current ratings for diode D3 and the speed switch. As far as the switch is concerned, you could either leave it out altogether or substitute a bigger the substitute microphone? I have found a software-based pink noise generator at: http://www. nch.com.au Can this be used in place of the pink noise kit? Also I’m not clear on the calibration procedure. It says to connect the pink noise source to the mic input (I assume with the mic disconnected?). Should this be the line level output from the pink noise source or the speaker level output; ie, should I use the line level output from the sound card or the wires that connect to the internal PC speaker? As the software will only go to -30dB, can I use 700mV as the set point; ie, a 300mV change between 0dB and -30dB? (V. S., via email). • The Jaycar Cat. AM-4011 microphone would be suitable. No resistor changes are necessary. The pink noise generator signal from the computer sound card would be suitable. However, the 60dB attenuator circuit as used in the SILICON CHIP Pink Noise genera­tor (January 1997 issue) would need to be used to calibrate the sound level meter. switch, such as the 10A 240VAC DPDT toggle switch from Jaycar (Cat ST-0575). To get a higher rated diode, you will need to go to a TO-220 package type such as the MUR1560 rated at 15A, 600V (Jaycar Cat ZR-1030). Make sure these components fit comfortably inside the case. Note, however, that these modifications will not let you run appliances with 10A ratings on their nameplates. To do that, you would need to use a larger diecast case or otherwise improve the heatsinking of the Triac. This resistive divider can be added to the output of the sound card. Does auto lock-up confuse Gear Indicator? I am interested in the Gear Indicator project featured in the January 2003 issue. I have a VR Commodore with a 4-speed auto and lock-up converter. What do you set the number of gears to? Four or five? As far as I’m aware, the converter locks up in third under certain conditions, as well as locking up in fourth. This being the case, what would the display indicate, because if you set it for five gears - ie, four plus one for lock-up - and the trans­mission locked up in third, would it confuse the display by showing the wrong gear? (P. B., via email). • The Gear Indicator should indicate the correct gear irres­pective of lockup in the torque converter. This is because the unit is calibrated when driving on a flat road at a steady speed and so the torque converter should have minimum slippage anyway. However, calibration in fourth gear may need to be done with the converter locked. If the unit is calibrated in fourth gear when there is slight acceleration and hence slippage in the torque converter, it may be possible to calibrate this as gear 4, with gear 5 when the converter is locked. That’s if that is what you want. Alternatively, you may be able to calibrate for lock-up in gear 3 (call it gear 4), if gear 3 is calibrated with the con­verter slipping. Then you could use the gear 5 and 6 numbers for fourth gear and fourth gear with lock-up. If we were doing it though, we would set it up just to indicate four gears and not worry about the lock-up condition. Notes & Errata PortaPAL PA Amplifier, February & March 2003: the main PC board (code 01103031) has an error which needs to be corrected. The link near pin 1 of IC5 connects on one side to ground but the other side is disconnected. It should go to the emitter of Q1 via the adjacent track. The end of the 18kΩ resistor adjacent to the open circuit link should be connected instead to the adjacent track which goes to pin 7 of IC5. A revised PC board pattern has been placed on our website and forwarded to kit suppliers. Solar Panel Regulator, March 2002: the PC board component overlay on page 85 shows diodes D1 & D2 mounted with metal sides down. They should be mounted metal side up, the same as the Mosfets. Speed Controller For Universal Motors, October 2002: the PC board diagram on page 17 shows a 5404 fitted as D3. This should be a 6A diode such SC as R250H or PX6007. 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. 92  Silicon Chip www.siliconchip.com.au