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Notes & Errata Spark Energy Meter, February & March 2015: the main circuit diagram shows D13 as a BAT46; this should be a 1N4004 silicon diode. The parts list should therefore be adjusted: 9 BAT46 diodes (not 10) and a 1N4004 added as D13. On the main component overlay (March), ZD31 is shown as 16V whereas it should be a 12V zener to agree with the circuit diagram and the parts list. On the Calibrator, if there is insufficient range adjustment for VR2 to set 250Hz, Ask SILICON CHIP . . . continued from page 103 you will get a nasty electric shock. If you are sure the construction is correct, then you can try using a 3A slow-blow fuse or 5A standard fuse instead of the 3A fuse. The initial surge current when power is applied can cause a fuse to blow. Hot snubber in speed controller I have built the Full-Wave Motor Speed controller from the May 2009 issue and 470Ω 1W resistor in series with the 47nF capacitor across the IGBT gets very hot. All voltages appear normal. Can you explain or suggest any reason? (D. M., via email). •  The resistor dissipates power as it charges and discharges the 47nF capacitor in the snubber network and so it runs hot. This is normal. You can change this resistor to a 5W type or use a smaller value capacitor such as 22nF 250VAC (X2 rated), if R1 can be changed to a lower (eg, 180kΩ) or higher (eg, 270kΩ) value, as required. CLASSiC DAC (February-May 2013): Fig.11 on page 39 of the April 2013 issue showed a 10Ω resistor to the left of Q11 which should be 2.2Ω. Also, the capacitors immediately below Q11 should be 220µF and 1µF. These are all shown correctly on the circuit diagram. The overlay dia­gram in the online edition is also correct. you are concerned about the resistor temperature. Ultrasonic transducer is unlikely to be faulty I have just completed building the Ultrasonic Anti-Fouling kit and on switching the unit on it blows fuse F1. Disconnecting and checking the transducer with an ohm meter, I get no reading across the red and black wires. Have I been sent a faulty transducer? What is my recourse in this situation? (R. G., via email). •  The ultrasonic transducer should read as an open-circuit when using a multimeter, as this is a piezo electric transducer that is essentially a capacitor when DC voltage is applied. So it is unlikely that the transducer is faulty. There can be several reasons why the fuse blows. Firstly, with the fuse and IC out of circuit, trimpot VR1 should be adjusted so there is 5V between TP0 and TP1. If this is not able to be adjusted correctly, check components for correct Advertising Index Altronics.........................loose insert Emona Instruments........................ 7 Hare & Forbes.......................... OBC Icom Australia.............................. 41 Jaycar .............................. IFC,49-56 KCS Trade Pty Ltd........................ 25 Keith Rippon .............................. 103 LD Electronics............................ 103 LEDsales.................................... 103 Master Instruments.................... 103 Mastercut Technologies.................. 9 Microchip Technology..................... 3 Mikroelektronika......................... IBC National Instruments...................... 9 Ocean Controls.............................. 8 Qualieco....................................... 59 Questronix.................................. 103 Radio, TV & Hobbies DVD............ 91 Sesame Electronics................... 103 Shapely Design.............................. 5 Silicon Chip Binders................ 76,97 Silicon Chip Online Shop............. 37 Silicon Chip Subscriptions........... 77 Silvertone Electronics.................. 10 Tronixlabs................................... 103 Wiltronics...................................... 11 Worldwide Elect. Components... 103 X-ON Electronic Services.......... 103 orientation and position. Make sure the wire link (Link 1) is in place or alternatively a 0Ω resistor in the Link 1 position. Check for solder bridges that shouldn’t be there and unsoldered joints. Before inserting the fuse and IC2, check that the 2200µF electrolytic capacitor is orientated correctly (plus SC side toward the fuse). 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 Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. 104  Silicon Chip siliconchip.com.au