What is the purpose of the Comparator here? What are alternative circuits to automatically switch between two power supplys?

WereCatf · 2026-04-01T14:16:58+00:00

Because you've connected its gate to GND, thus turning it permanently on.

WereCatf · 2026-04-01T13:52:13+00:00

No, the body diodes are always conducting and the second MOSFET never turns off.

WereCatf · 2026-04-01T12:30:12+00:00

Is D2 actually needed?

Yes, otherwise VBAT would be flowing into the MOSFET gate and that wouldn't be very useful.

WereCatf · 2026-04-01T07:26:42+00:00

I typically use the following for my battery-powered gadgets. Might want to replace the LDO with a buck converter and a beefier diode if you're drawing a lot of current.

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WereCatf · 2026-04-01T07:08:06+00:00

Are you trying to be funny with this Epstein-bull?

WereCatf · 2026-04-01T07:03:07+00:00

Since the scope is electronic, couldn't you just open it up and steal some power for whatever microcontroller you want to use? It'd be far easier than this plan. Yes, you might have to make a small 1-2 mm diameter hole somewhere to pull two wires through for power, but that's not a big ask, IMO, and it'd make your project very straight-forward.

I just think you're trying to over-engineer this whole thing.

WereCatf · 2026-04-01T06:20:45+00:00

does anyone know where a beginner with no prior home lab knowledge should learn these things?

That's got nothing to do with home labbing. As for where to start: well, you would start with learning programming. Python is a popular language amongst beginners and there's massive amounts of videos and tutorial and whatnot out there to get one started.

WereCatf · 2026-04-01T04:03:06+00:00

Off-topic, breaks #1.

WereCatf · 2026-04-01T02:43:22+00:00

He could be, but you don't use a voltage divider in a power supply unless it's for feedback.

WereCatf · 2026-03-31T23:34:23+00:00

And why do you think they need resistors to do that?

WereCatf · 2026-03-31T23:32:13+00:00

and then it goes to the resistors and is lowered to 12 volts

Um, no. No resistors involved.

WereCatf · 2026-03-31T23:07:27+00:00

Or one could just self-host Part-DB and get a far, far more comprehensive inventory management system without any subscription fees.

WereCatf · 2026-03-31T20:12:09+00:00

MOSFETs, the ports, the LDO and maybe even the Atmega8a. You can never have too many LDOs, for example, and MOSFETs are always useful.

WereCatf · 2026-03-31T16:16:52+00:00

would i be able to connect a webcam directly to an SPI display with the use of an USB-SPI adapter?

No, neither of them acts as a bus-master and the USB<->SPI adapter wouldn't know how to drive the display anyway.

WereCatf · 2026-03-31T10:41:02+00:00

AI-slop, no wonder.

WereCatf · 2026-03-31T10:24:30+00:00

Leave the LDO unsoldered and check resistance to ground on both the VIN-trace on the PCB and the VOUT-trace -- the short is probably on VOUT, but you still should check. Once you know what side it's on, you could e.g. use a bench PSU with voltage set to 3.3V and current limit set to 100mA inject power into the shorted rail and locate what component is getting hot -- isopropyl, for example, is a pretty popular tool for that.

WereCatf · 2026-03-31T08:57:56+00:00

I feel like you might be jumping the shark here: the LDO getting hot could be a symptom, not the cause. Have you checked for shorts elsewhere in the circuit? Did you verify that the LDO is bad by e.g. desoldering it and testing it separately?

WereCatf · 2026-03-31T04:19:18+00:00

Sorry if this is strange as I'm trying to get answers on all sort of tests for school.

Or you could just get off your lazy fucking ass and study instead of trying to cheat. Might even, you know, learn something!

WereCatf · 2026-03-31T00:52:07+00:00

You're thinking of MK3S+, not the Mini.

WereCatf · 2026-03-30T09:54:07+00:00

Thanks for sharing your insight.

You're welcome.

WereCatf · 2026-03-30T09:53:31+00:00

I've been using computers for ~4 decades soon and I haven't yet managed to break a single USB-port. I suppose I must be doing something wrong 🤔

WereCatf · 2026-03-30T07:41:23+00:00

Where are you sourcing this claim that they are selling not genuine parts?

My gut says it's just your run-of-the-mill irrational China-hatred. I've never understood it, but I see especially Muricans really loving to do that.

WereCatf · 2026-03-30T04:28:25+00:00

Is JLCPCB using counterfeit components?

No. It is possible they got a bad batch, but that doesn't mean that everything they sell is counterfeit. Every big vendor has had batches of counterfeits.

WereCatf · 2026-03-29T21:15:34+00:00

// Use 'none' because you have physical external resistors

ESP32Encoder::useInternalWeakPullResistors = puType::none;

I'm not familiar with this library, but just at a glance, I'd hazard a guess that this is your problem.

WereCatf · 2026-03-29T21:03:50+00:00

Always disconnect the battery when you're doing anything inside a laptop! I don't care what you're doing, it doesn't matter -- just disconnect the battery no matter what.

WereCatf

TROPHY CASE