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Notes & Errata


Crystal DAC, February 2012: (1) The original PCB has the trimpots rotating in the opposite direction to that stated in the article, ie, clockwise rotation decreases the quiescent current rather than increasing it. A modified PCB file has been uploaded to the website which fixes this problem. Constructors using the original PCB should rotate both trimpots fully clockwise before applying power for the first time. (06/12)

(2) The trimpots were specified as 500 ohms but should in fact be 5k ohms. This affects the circuit diagram, PCB overlay and parts list. Also, the labels for Q22 and Q23 are swapped on the overlay diagram (Fig.6, page 32). (07/12)

1.5kW Induction Motor Speed Controller, April-May 2012: (1) The PCB overlay diagram (May, p69) shows two 270-ohm resistors below IC3 which should have been labelled 100 Ohms (their value is wrong in the parts list too). Also, the circuit diagram (April, p22) shows the three pull-up resistors for the pins of CON5 (two 4.7k and one 1.5k) all connected to pin 1 of CON4. They are actually connected to the +3.3V rail. Finally, the Altronics catalog number for the 470uF 400V capacitors in the parts list is incorrect. It should be R5448. (06/12)

(2) A number of changes must be made to the original PCB to ensure reliable operation. These changes are described in the December 2012 issue. In addition, one of the holes is incorrectly positioned on the heatsink drilling diagram. A corrected drilling diagram is shown on page 83 of December 2012. (12/12)

PIC/AVR Programming Adaptor Board, May-June 2012: Since this circuit was designed, Microchip have released a number of new PICs, many of which can be programmed using this board. This includes the PIC16F150x series (four chips). These can be programmed in mode B, not mode C as is implied by Fig.5 on page 78 of the June 2012 issue. For other new PICs, check the data sheet and compare the programming pin location and supply voltage requirements to that of other micros listed in Fig.5. (11/12)

Crazy Cricket/Freaky Frog, June 2012: The Jaycar buzzer part number is incorrectly listed in the parts list. It should be AB-3440. (07/12)

Mix-It! 4-Channel Mixer, June 2012: Fig.8 on page 67 should show the top switch connecting to signal ground and the bottom switch going to pin 7 of IC1b (not the other way round). (08/12)

Wideband Oxygen Sensor Controller, June-August 2012: (1) he parts list in part 1 (June, p42) includes two 3.5mm stereo jack plugs. Delete these and substitute two PCB-mount 3.5mm stereo switched jack sockets. (07/12)

(2) On the PCB, the anode of ZD1 does not connect to the adjacent ground track as it should. The PDF file on the website has been corrected to fix this. If you bought a PCB from the first batch, bend the lead of ZD1 over and solder it to the negative (lower) pad of the adjacent 10uF capacitor or fit a wire link between these two pads. Ensure it cannot come in contact with any other nearby pads. (09/12)

Soft Starter For Power Tools, July 2012: The X2 capacitor specified in the parts list is a tight fit on the PCB. Element14 part code 1215460 is a better fit, as is the Altronics R3129. (08/12)

Using Two PC Power Supplies for 24V, Circuit Notebook, August 2012: Most PC power supplies have their output ground internally connected to earth. For this circuit to work, one supply must have floating outputs. The low-voltage ground is normally earthed through one or more solder pads under the screw heads holding the internal PCB to the earthed metal case. Typically, the supply will still operate if these earth connections are broken (eg, by using insulating washers under the screw heads). Do NOT disconnect the mains earth at the input socket as the metal housing must remain earthed, as should any EMI suppression components. Care must also be taken if a PC power supply is opened up as they contain large, high-voltage capacitors which can retain a lethal charge for some time and they often have exposed mains and high-voltage DC components. (09/12)

Barking Dog Blaster, September 2012: (1) The 10 ohms resistor shown on the overlay and PCB screen print to the right of the S2 start switch terminals should be a 100 ohms resistor to match the parts list and circuit. (12/12)

(2) The Fig.2 overlay diagram shows the LED package (LED1) with the incorrect orientation. The anode marking (A) is in the correct position but the LED flat side should be toward the lower edge of the PCB. (01/13)

Induction Motor Centrifugal Switch Over-ride, Circuit Notebook, September 2012: There is an error with this circuit. When changing motor speeds, the run LED (in the controller) flickers and in some cases retriggers the 555 (IC1). To fix this, the 10nF capacitor across the 10M ohms resistor should be changed to a 4.7uF electrolytic and connected via a 1N4148 series diode to pin 10 of the PIC (anode to pin 10). The positive side of the electrolytic goes to the cathode. Also when using this circuit, it is best not to set the motor speed below about 25% as the LED can go out completely and retrigger the 555. (10/12)

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