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VXO7805 on the power board and the linear 7805 on the ESP32/display board are bridged via the 20-pin ribbon cable on pins 18 & 22. This seems a bit odd and perhaps an oversight. If these hadn’t been bridged, the over-voltage would have been limited to just the power boards. I’ve cut the link between pins 18 & 20 on the ESP display board now. I have also compiled the source myself on the more recent Arduino IDE 2.3.9 under Linux. This required a few fixes that I have made and published as a pull request to Richard’s GitHub Advertising Index Altronics.................................47-50 Blackmagic Design....................... 7 Dave Thompson........................ 103 DigiKey Electronics..................OBC Emona Instruments.................. IBC Hare & Forbes............................... 9 Jaycar.................. IFC, 14-15, 28-29 Keith Rippon Kit Assembly....... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology.................. 5 Mouser Electronics....................... 3 PCBWay....................................... 11 PMD Way................................... 103 Practical Electronics PDFs......... 69 SC Micromite Explore-40......... 103 SC Ideal Bridge Rectifiers........... 73 SC RP2350B Computer.............. 95 Silicon Chip Binders.................. 38 Silicon Chip PDFs on USB......... 58 Silicon Chip Shop.................96-97 Silicon Chip Songbird................ 80 Silicon Chip Subscriptions........ 39 The Loudspeaker Kit.com............ 8 Wide Technical.......................... 103 Wagner Electronics..................... 87 Next issue on-sale date Next Issue: the September 2026 issue is due on sale in newsagents by Monday, August 24th. Expect postal delivery of subscription copies in Australia between August 24th and September 11th. 104 Silicon Chip repo. These fixes include removing Richard’s home WiFi credentials from the WiFi secrets header file. I hope this is useful to others. I note, and have commented in Richard’s bug report, that there is a design bug with Kelvin mode that can cause damage to the INA232. I’d like to know more about this and whether I can help resolve the issue. (R. E., Dover Gardens, SA) ● Richard Palmer responds: there are two problems with the PCB layout that were noted in Silicon Chip’s Notes & Errata in the December 2022 issue: a via that is too close to a track and the voltage regulator pin reversal. From your letter, you have discovered the second problem the hard way. I have added an illustrated version of the errata to the GitHub repository for this project (https://github.com/ palmerr23/ESP32-DCLOAD/tree/ main/errata). Regarding Kelvin sensing, when the negative Kelvin sensing terminal is connected to the DUT, any resistance in the negative current lead will induce a negative voltage at the Kelvin terminal, which is connected directly to the ADC’s negative input. It is not a problem if the main +/− terminals are used to measure voltage as well as current. In that case, the ADC’s negative input will be connected to local ground via the 390W resistor. The updated document in the repository explains the concern in more detail and provides a solution, as well as a few minor circuit and software improvements suggested by two readers. 2007 issues (siliconchip.au/Series/56) and have a question regarding the operation of the software “ignprgm.asm”. I intend to use a MAP sensor for load determination and would like to understand how you normalise or average the MAP sensor voltage. The MAP sensor response will be relatively fast and will contain considerable peaks and troughs, particularly at idle. Lowering the ADC gain would probably not give me the resolution I would need for an engine with low vacuum (aggressive cam). I have gone through the source code and can find the ADC but cannot find where the MAP sensor voltage is ‘treated’, if indeed it is. I prefer not to use a TPS signal for load, and external hardware filtering (R/C) will introduce delays. Any insights you have would be appreciated. (G. M., Vermont, Vic) ● The load value as measured from the MAP sensor isn’t averaged. Due to the quick response required, the load is read in real time without adding any delay by software averaging or hardware averaging. The air pressure measured by the MAP sensor at that time is the one used to adjust timing. There isn’t any way to introduce averaging without affecting response time. The beginning of the code for the MAP sensor read is at line 1693: MEAS_LOAD ; measure LOAD input ; set A/D to channel 2 movlb D’1’ movlw B’00001001 movwf ADCON0 call ACQUIRE_AD movf A_DRESH,w movwf LOAD_D_A Alternative LCD for 8-digit Frequency Meter Modifying Flexitimer I want to build the Compact 8-digit for 0-60 minutes Frequency Meter from August 2016 (siliconchip.au/Article/10037) but Jaycar has discontinued supply of the LCD screen. Their replacement is completely different in all respects. Where can I get a compatible device? (J. A., Townsville, Qld) ● The Altronics Z7013 screen specified as the alternative in the parts list is still available. MAP sensing for programmable ignition I am building your Programmable Ignition System from the March-May Australia's electronics magazine Can the Jaycar Flexitimer kit (KA1732), based on the article from Electronics Australia, March 1991, be modified to produce a timer adjustable from 0 to 60 minutes? (R. M., Melville, WA) ● The Flexitimer circuit can produce a timeout of one hour using the Q13 output with RV2 set at mid-travel, but a timeout close to zero is not possible with this timer unless you choose a lower counter output from the 4020 counter IC, and even then, it will not be that close to zero. A digital timer would be a better choice for such a SC requirement. siliconchip.com.au