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Advertising Index Altronics.................................49-56 Blackmagic Design....................... 7 Control Devices........................... 37 Dave Thompson........................ 111 DigiKey Electronics....................... 3 Electronex................................OBC Emona Instruments.................. IBC Hare & Forbes............................. 11 Icom Australia............................. 99 Jaycar....................IFC, 9, 22-23, 65 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology................ 43 Mouser Electronics....................... 4 OurPCB Australia.......................... 8 PCBWay....................................... 47 PMD Way................................... 111 Rohde & Schwarz........................ 45 Silicon Chip Shop................ 77, 81 Silicon Chip Subscriptions........ 95 The Loudspeaker Kit.com.......... 10 Wagner Electronics................... 103 Notes and Errata Pico/2/Computer, April 2025: boards with CH334F chips marked 13122E20 will not work unless resistors R54 and R55 are removed. Boards we sell with matching chips will come with those resistors removed so they function correctly. CH334F chips with batch code 1163FD43 are not affected and will work with the resistors in place. Surf Sound Simulator, November 2024: in the circuit diagram (Fig.2), the 56nF capacitor connected to pin 9 of IC2c should instead be connected from the anode of D5 to pin 9 of IC2c. The overlay diagram and PCB is correct. In the panel on p51, the two references to pin 8 of IC1d should say pin 14. Next Issue: the June 2025 issue is due on sale in newsagents by Thursday, May 29th. Expect postal delivery of subscription copies in Australia between May 26th and June 16th. 112 Silicon Chip IC1 is connected to the 0V supply via 100W when S1 is switched to the soft start position and that pin 4 is tied to the +5V supply rail via a 47kW resistance when S1 is open (soft start is off). Also check that pin 4 of IC1 is properly inserted into the socket and not bent under the package. LC Meter relays not switching I am testing the Digital Wide Range LC Meter (June 2018; siliconchip.au/ Article/11099) but I am encountering problems as the instrument does not indicate any values of either capacitors or inductances. I think the problem is the reed relays not switching. I have verified that the output voltage from the Arduino pins drops to 0.8V, but I cannot verify the reed contact closure. I have checked the coil current is 12mA, which seems normal. The firmware on the micro is OK. The problem could also be the comparator; I will check its output with an oscilloscope. (M. F., Scandicci, Italy) ● We don’t think the output voltage from the pins should drop that low; it should stay fairly close to 5V when the relays are being driven. We suspect your reed relays have an intrinsic diode that is shunting the current away from the coil. The circuit was designed to use relays without diodes, but similar relays are available with such diodes. If this is the case, you are not the first to have had this problem. A significant proportion of the problems reported with the LC Meter have been due to the incorrect relays being used, and changing to different relays fixed the problem. It would help if you could send some photos of your construction, including the part numbers on the relays. That will also allow us to see if there are any other potential problems. Universal Loudspeaker Protector resistor value I am currently building the Universal Loudspeaker Protector Mk3 (November 2015 issue; siliconchip. au/Article/9398). The parts list and the SMD parts set I bought from the Silicon Chip Online Shop (SC3217) includes a 5.6kW M3216/1206 SMD resistor. However, the circuit shows a 6.8kW resistor between pins 5 and 9 Australia's electronics magazine of the LM339, and the PCB mask also has 6.8kW. Is it OK to use the 5.6kW resistor instead? (J. B., Hataitai, New Zealand) ● According to the text in the righthand column on p67, 5.6kW is the correct value and gives fan-on/overheat thresholds of 65°C/75°C. Using a 6.8kW resistor gives slightly lower fan-on/ overheat thresholds of 60°C/70°C, but in that case, the 15kW resistor should be changed to 18kW. The value was changed to 6.8kW at the last minute and the 15kW resistor was changed correctly but we missed changing the 5.6kW resistor in a couple of places. WiFi Weather Logger Arduino compiler error While compiling the firmware for the WiFi Weather Logger (December 2024; siliconchip.au/Article/17315), I got some errors from the Arduino IDE. I fixed them by changing D8 to 15 and D4 to 2 on lines 10 and 15 of the code. Otherwise it worked ‘out of the box’. (R. L., Wareemba, NSW) ● We tried to replicate your error but were unable to, using the latest version (3.1.2) of the ESP8266 board profile, version 2.3.3 of the Arduino IDE and the “LOLIN(WEMOS) D1 R2 and Mini” board definition as per the article. If we change the board definition to something like the Generic ESP8266 Module, then we get these errors (amongst others): WIFI_WEATHER_LOGGER.ino:11:17: error: ‘D4’ was not declared in this scope WIFI_WEATHER_LOGGER.ino:10:19: error: ‘D8’ was not declared in this scope; did you mean ‘s8’? So we think you may be using the wrong board definition or the board definition is corrupted on your computer. You can find these pins definitions on Windows in “[user directory]\AppData\Local\Arduino15\ packages\esp8266\hardware\ esp8266\3.1.2\variants\d1_mini\ pins_arduino.h” and they are set as follows: static const uint8_t D4 = 2; static const uint8_t D8 = 15; If this file is missing/corrupted, that may be the cause of your errors. SC siliconchip.com.au