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Advertising Index Altronics.................................27-30 Dave Thompson........................ 103 DigiKey Electronics....................... 3 Emona Instruments.................. IBC Hare & Forbes............................. 17 Jaycar............................. IFC, 49-56 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology......... 7, OBC Mouser Electronics....................... 4 SC Advanced Test Tweezers.... 100 SC Breadboard Power Supply.... 26 SC GPS Analog Clock............... 101 SC Pico W BackPack.................. 79 Silicon Chip Back Issues............. 8 Silicon Chip Shop.................42-43 Silicon Chip Subscriptions........ 48 The Loudspeaker Kit.com.......... 77 Tronixlabs.................................. 103 Wagner Electronics....................... 9 104 Silicon Chip The only thing that had changed since I first built the adaptor and when I found it not working last week was that the 9V battery had gone flat. (M. R., Middle Park, Vic) ● First, measure the voltage across the supply pins on IC3, pins 7 and 4. Probe the IC pins where they go into the package in case the socket or soldering is a problem. If the supply voltage is getting to the chip, but there is no output on pin 6, either the chip is faulty or input signals are not reaching it. If it has power and there is continuity between IC3’s pins 3/2 and the SENSE+/SENSE− terminals, then you will need to replace IC3. Using one charger for multiple batteries Have you ever published a circuit for a battery charger output switcher? I run a smart charger on my batteries in the shed: car, lawnmower, tractor, boat etc. All these batteries need to be maintained by switching the leads from one to the next. A circuit that switches a charger between all these batteries with a programmed timing cycle would make a good project. (Craig, via email) ● We haven’t published a sequencer timer like that. However, if you can accept that each battery is connected to the charger for the same period, you could use a circuit like the Circuit Notebook entry “One-in-five timer” (June 2009; siliconchip.au/ Article/1459). It comprises a 7555 timer and 4017 counter. The output drives a transistor that powers a relay. The relay could be used to switch the charger to the required battery. The transistor and relay circuitry can be duplicated and connected to the subsequent 4017 out- Errata & Sale Date for the Next Issue I have double-checked everything, put a new 9V battery in and rechecked the initial four setup adjustments. Adjusting VR1, VR6, VR2 and VR3 all produced responses as expected. I also rechecked the voltage null detailed in the “final setup” instructions, and the voltage responded as expected; it was easy to set it to zero. However, the final setup test using VR4 and a known 10W resistor was a complete failure. I got no voltage readout and could not obtain any voltage change by varying VR4 across its entire range. I attempted this setup for both a 4-terminal and 2-terminal test with the same result. I have triple-checked all my cables, the Milliohm Adaptor switch settings, DMM settings, the PCB itself for shorts or broken tracks and the orientation of all components on the PCB. Everything is spot on. I also tried three different DMMs with the same results. All parts of the circuit appear to be responding correctly except the output from IC3 (AD623AN). Is it possible the AD623AN has gone faulty? Or can you think of another reason I cannot get an output from the Milliohm Adaptor to my DMMs? put for more than one battery. You can use this circuit for up to 10 batteries. The reset section is set up to go back to the first output after a count of five, but you could change how it is connected to the 4017 to give a different number of steps. The 7555 timer frequency sets the period. Its output would probably need to be divided down by a frequency divider, such as a 4020, to get the desired battery charging period. Increasing mains timer duration I purchased and constructed the ‘Mains Timer for Fans and Lights” from an Altronics kit (K6047). This is a Silicon Chip project, but I don’t know when it was published. I am using it to switch off a water pump after a pre-set time. If I forgot and left the pump running, we could send huge volumes of precious rainwater into the paddock. Can C1 be replaced with a value larger than 330nF to increase the maximum time to more than one hour? I am considering finding a capacitor near 600nF or 700nF to increase the maximum time to around two hours. Thanks for the enjoyable, informative read every month. (D. R., Goughs Bay, Vic) ● You can find out when the design for a kit was published by searching for the kit code here: siliconchip.au/ Articles/ContentsSearch That project is from the August 2012 issue. Yes, you could increase C1 above 330nF to get a delay over one hour as it determines the oscillator frequency. Note that such long delays may not be too accurate; 680nF is a reasonable choice if you’re aiming for around two hours. SC Reciprocal Frequency Counter, July 2023: on the PCB, test point TP3 actually connects to pin 12 of IC1a (same as TP2), not pin 5 of IC2a as shown in the circuit diagram. If you need to monitor the COUNTEN signal, probe the Arduino Nano D3 pin. Wideband Fuel Mixture Display, April-June 2023: some PCBs supplied have diode D2 incorrectly labelled as D5. On those same boards, the 100nF capacitor just below IC3 lacks a proper pad to solder its lead to on the underside. It can be bent over and soldered to the pad for the nearby 100nF SMD capacitor on the underside. Also, in Fig.15 on p75 of the June 2023 issue, the mauve “A/F” wire going to the multimeter should connect to MV+, not MS+ as shown. Next Issue: the October 2023 issue is due on sale in newsagents by Thursday, September 28th. Expect postal delivery of subscription copies in Australia between September 26th and October 13th. Australia's electronics magazine siliconchip.com.au