Some thoughts and observations after a first run\n<\/p>\n\n\n\n
First and foremost, I poorly dimensioned the ESC since the afroESC 30A is rated LiPo 4s (14.4V), while the panel VOC<\/sub>\n is about 22.5V and the maximum power voltage under good lighting \ncondition is about 18.6V. I was hoping the voltage would drop rapidly \nwhen drawing power, but this is not so the case, so I’m gonna switch to \nthe spider 30A (rated 6s). Rightly or wrongly, I’m not expecting any \n“burn” problem because, unlike a battery, a solar panel is a current \nlimiting (theoretically a constant current) device, so the current won’t\n go beyond 11A with 2 panels, whatever happened.\n<\/p>\n\n\n\n I’ve\n been using the Attopilot 90A, because it’s rated 50V, while my \nunderstanding is that the 45A version is only rated 13.6V. The 90A \noutputs 36mV\/A, that is one unit read on the ADC (10 bits for 3.3V) is \nabout 100mA, not precise enough. Furthermore, the signal on the “I” pin \n(current reading) appears very unstable when the motor is rotating (this\n of course is the motor, not the Attopilot), and it seems to me the \nresponse is non linear with low amps (< 300mA), so this doesn’t \nreally fit my needs. I’m considering switching to an ACS712 based \nbreakout board for the current measurement “to see”. In that case, I’ll \nhave to do the voltage measurement, but this is just a voltage divider, I\n can do this by myself.\n<\/p>\n\n\n\n At first, current reading wasn’t working the way I expected. \nAfter some measurements, I got a 20mV voltage between the ground pin of \nthe Attopilot logic circuit and the power ground. WTF ??? Most likely \nthe current from the Attopilot “I” pin flowed back to the switching \nregulator ground to a certain point. Might be because the wires between \nthe Attopilot and the switching regulator input are quite long thick AWG\n 14 (they should sustain at least 12A…), making place for some \nparasitic capacitance (otherwise the two points would be \nshort-circuited, leaving no way for a voltage difference). Anyway, I \nadded a wire between the 2 “grounds” and everything went into order. \nClassic multiple power paths problem.\n<\/p>\n\n\n\nMeasuring power<\/h1>\n\n\n\n