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4mA current flowing back from the battery to the controller. Is that normal? Have you ever published an MPPT solar charger that would suit a 32V 200Ah battery being charged from three standard 20V solar panels? (R. W., Loxton, SA) • The amount of current drawn by a charger from the battery depends upon the circuit design. It is normal for there to be some current drawn by the controller (whether it is an MPPT charger or not). After all, the charge controller circuit needs power to operate, and that can only come from the battery when there is no solar power available. The 4mA drain is not huge compared to the overall battery capacity – it would take nearly 290 days to fully discharge your battery at that rate. However, the less the charger draws from the battery, the better. Unfortunately, we have not published an MPPT solar charger to suit a 32V lead-acid battery. That is a somewhat unusual voltage; 12V, 24V, 36V and 48V are more common. It’s close enough to 36V that a charger designed for a 36V lead-acid battery might work; as long as it’s adjusted. Modifying the 40A DC Motor Speed Controller I have a customer who is using a number of your March-April 2008 40A DC Motor Speed Controllers (siliconchip.com.au/Series/48) to vary the speed of trolling motors on their boat. They want to speed up the soft-start ramp or remove it. Currently, the soft start runs for about 10 seconds, but they need it to be under three seconds. I’ve had a brief look at the assembly code for it, but my knowledge of assembly is so rusty it would take months to dissect it. I did have a go at assembling the source code which is available for download from your website, but I got several errors regarding missing functions named float_ascii2 and float_ascii4. They don’t appear to be part of the standard library. I also found that I had to add these two lines at the top of the main .asm file, which got rid of several other errors: #define P16_MAP1 0 #define P16_MAP2 1 I know that you have since released a more modern speed controller which has the soft-start control they’re after, but they’ve already built these kits and have been using them for a little while. We didn’t make a kit of the updated one so it would still be a fair amount of running around for them to switch. (Tom Skevington, Kits Manager, Altronic Distributors) • The float_ascii2 and float_ascii4 functions were in another file which was not included in the ZIP download for that project. That has now been corrected. Thanks for the tip about the two added defines which are needed. The software has two variables in which values are stored to increase or decrease the PWM duty cycle, named pdeltah and pdeltal. These are loaded with +1 on lines 819-821 of the main ASM file to decrease the speed, or -1 on lines 824-827 to increase the speed. Since this gives a soft start time of around 10 seconds, changing the increments to +4 and -4 should give a ramp time of around 2.5 seconds. To achieve this, change line 819 to: movlw 0x04 movlw 0xFC and change line 824 to: This will also make the motor speed ramp more quickly in response to the rotation of the speed control pot, or changes in load (ie, feedback). SC Advertising Index Altronics...............................81-84 Ampec Technologies............. OBC Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.................. 5 Ocean Controls......................... 11 Premier Batteries........................ 8 RayMing PCB & Assembly........ 10 Rohde & Schwarz........................ 7 SC Vintage Radio DVD.............. 34 Silicon Chip Christmas Kits...... 52 Silicon Chip Online Shop....98-99 Silicon Chip PDFs on USB....... 25 Silicon Chip Subscriptions....... 35 The Loudspeaker Kit.com........... 9 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 63 Notes & Errata Digital Lighting Controller pt2, November 2020: on p101, the parts list correctly includes a 27W 1W resistor for the Micromite master unit but incorrectly lists it as 25W 1W for the CP2102 Adaptor module (it should also be 27W 1W). Tiny LED Christmas Ornaments, November 2020: the parts list incorrectly lists the Bauble PCB dimensions as 91 x 98mm when they should instead be 52.5 x 45.5mm. Also, the Cane PCB is incorrectly listed as 84 x 44mm when it should be 84 x 60mm. Two new 7-band Audio Equalisers, April 2020: in the first batch of stereo equaliser PCBs sold (code 01104202), the connection between the 220pF capacitor and 51kW resistor in the lower right-hand corner of the board went to the top of the resistor instead of the bottom (which was floating). This can be fixed by cutting the track between the two components and running a short wire from the bottom of the resistor to the nearest pad of the capacitor. PCBs sold from November onwards do not have this problem. The January 2021 issue is due on sale in newsagents by Thursday, December 31st. Expect postal delivery of subscription copies in Australia between December 27th and January 15th. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au