Yes, it is direct to 100Ah batteries. On Fri, Mar 1, 2019 at 5:04 PM Ken Hohhof <af...@kwisp.com> wrote:
> On quick inspection, I’m a little uncomfortable with IC2 comparing USB > voltage to the 3.3V output, it seems kind of like the decision on how to > generate the 3.3V depends on the existence of the 3.3V, so maybe an > unintended feedback going on. As long as USB voltage is present, it should > power the regulators via Schottky diode D1. But without USB voltage, > couldn’t both inputs to the comparator be approx. zero? So does it turn Q1 > on or not? Or do you get an unstable situation? Seems like once Q1 turns > on there should be 3.3V present and things should be OK, but still feeling > uncomfortable about the situation. Maybe like Chuck said, manually drive > the gate of Q1 and see if things work as planned. > > > > I also have to ask, is this actually connected to 12V direct from a car > battery? With a bazillion amps available? If so, I’d kind of like to see > some resistance between Q1 and C6 to limit the current. Not saying this is > the cause of your problem. > > > > > > *From:* AF <af-boun...@af.afmug.com> *On Behalf Of * > can...@believewireless.net > *Sent:* Friday, March 1, 2019 1:13 PM > *To:* AnimalFarm Microwave Users Group <af@af.afmug.com> > *Subject:* Re: [AFMUG] OT: EE Consultant > > > > Schematics attached. The main issue I'm having is when powered via USB, > everything works fine. When powered via a 12V car battery, the > > chips seem to not have enough power. There are two comparator circuits, > one to monitor USB/Batt and report how the unit is being powered. > > The 2nd actually provides the power. One chip will occasionally draw > ~150-400ma of power causing the board to lock up. Chips are powered > > via Vin. > > > > What I don't understand is why everything works perfectly on USB but has > issues when powered via 12V. > > > > On Tue, Feb 26, 2019 at 11:53 AM <ch...@wbmfg.com> wrote: > > Circle of stability, miller capacitance all good stuff. > > > > *From:* Mark Radabaugh > > *Sent:* Tuesday, February 26, 2019 9:48 AM > > *To:* AnimalFarm Microwave Users Group > > *Subject:* Re: [AFMUG] OT: EE Consultant > > > > Oh sure, now you probably want me to believe transistors have states other > than off and on. > > > > Mark > > > > On Feb 26, 2019, at 11:20 AM, Ken Hohhof <af...@kwisp.com> wrote: > > > > > And good luck finding an analog circuit guy anymore ;-) > > > > That’s what I was. Not much demand, that’s why I’ve been doing other > things for over 20 years. Actually made the switch to engineering > management in the 80’s but still did some design work for another 10 years > because all the engineers wanted to do digital and processor designs. I > still have the books, the brain is rusty though. > > > > I tried to convince the new engineers that high speed digital design meant > knowing analog, RF and microstrip techniques, but they weren’t buying it. > Getting their products through regulatory emissions testing did give them a > bit of religion. > > > > I still remember laying out PCBs using red and blue tape. > > > > *From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Mark Radabaugh > *Sent:* Tuesday, February 26, 2019 9:09 AM > *To:* AnimalFarm Microwave Users Group <af@af.afmug.com> > *Subject:* Re: [AFMUG] OT: EE Consultant > > > > Yep - I’m qualified to answer some things and would be totally lost on > others. EE has become a huge field with many many disciplines. > > > > And good luck finding an analog circuit guy anymore ;-) > > > > Mark > > > > On Feb 26, 2019, at 9:56 AM, Ken Hohhof <af...@kwisp.com> wrote: > > > > Analog? Digital? Even with those there tend to be specialties like > emissions, safety, PLD/ASIC design, microprocessor/microcontroller, RF, > etc. Or do you need a generalist? > > > > *From:* AF <af-boun...@af.afmug.com> *On Behalf Of * > can...@believewireless.net > *Sent:* Tuesday, February 26, 2019 8:33 AM > *To:* AnimalFarm Microwave Users Group <af@af.afmug.com> > *Subject:* [AFMUG] OT: EE Consultant > > > > Having an issue with a circuit design, anyone know a good electrical > engineer they can > > recommend? > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > ------------------------------ > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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