Ask Electronics

Besides putting too many devices on a single wall socket, that draw too much power, what is supposed to happen?

Like say I chain ten dividers and put a single vacuum cleaner at the end. Is that more dangerous than plugging it directly into the wall?

I have a Mission MS 200 Subwoofer where the power supply has stopped working. I was quite happy with it, and would like to try to fix it, also I don't have the money for another. I have taken it apart and have narrowed the fault down to the PSU. I have visually inspected the solderings and components, and nothing obvious is wrong. I am not good enough to be able to reverse engineer the board, and was hoping there might be someone here with access to a schematic? Failing that, any pointers on where to maybe do some in-circuit measurements to narrow down which part(s) might be broken, would be very highly appreciated!

I'm trying to understand what's happening in this circuit:

I------------------T1 (+333V)
I                 I
I                 R1(10K)
(pos)             I
1000V             I------------gnd (0V)
(neg)             I
I                 R2(10K)
I                 I
I                 IT2(-333V)
I                 I
I                 R3(10K)
I                 I
I-----------------IT3 (-666.7V)

I am learning basic DC theory from reading and sometimes I come across something I'd like to ask a question about, so:

1. In the above circuit, without the ground, the voltage across all components would begin at 10V and finish at 0V. By adding a ground, I'm basically saying "here is 0V" and everything gets redefined in reference to that point and I end up with a 10 volt circuit with +3.33 as it's highest voltage and -6.667 as it's lowest.

2. The electrons could care less, they still flow from the anode to the cathode of the battery under normal conditions, going from the highest potential to the lowest.

3. This example was only used to demonstrate voltage dividers. It revolved around worker protection present in aluminum processing. Each machine is in series and mobile grounds are used nearest the machine a worker is using. I assume that this allows the worker to have the least exposure to electrical shock as they are also at ground potential?

I actually think working though these questions has cleared everything up, but please, comment on anything I got wrong.

Also, sorry about the crappy drawing, the autowrap in this editor really made things tough to format

Thanks!

I want to build a linux(yes i want linux specifically or a deritive of it) smartwatch as a prototype that lasts ~24 hours. Ive been looking for chips that are small and power effient enough but most of them cant run linux. If i have a 400mah battery that gives me a power budget of about 60mw... I know its possibly because there are wearos(basically android) watches that last 3-4 days. I dont know what kind of sorcery that is but that means it consumes about 15mw??? I really do feel like im miscalculating something but i checked multiple times. Do they hibernate linux/android and run it off of another chip. I also dont know how to excecute that properly and its kind of off topic of my question. So point is linux on a ~60mw budget in s smartwatch. I want to use a mip display as i really like the look and it uses little power but if ever want a heart rate sensor in it thats even more power consumpotion. Thanks in advance i guess if a saint answers this shitstorm of a question.

It happens rarely, but I will notice either my phone or the charger getting pretty toasty randomly. What could be causing this?

cross-posted from: https://sh.itjust.works/post/13637559

Hello everyone, I need some advice.

I am making custom PCBs for a project of mine. It's basically for a little remotely controlled robot using little DC motors. I chose the Seeed Studio XIAO ESP32C3 as the uC since it has inbuilt wifi/bt, 3.3V regulator that I can use to power the motors (can source up to 700mA) and lipo charging management (the robots will run on battery). As you can see from here, the microcontroller is surface mounted and the pads for the battery are on the bottom layer. Same story goes for the thermal pad of the microcontroller and the thermal pad of the motor driver (datasheet). I have worked with SMD components in the past and can solder them by hand, but I have never worked with SMD components that have thermal pads on the bottom layer. My question is: how to manage (route?) them? My PCB is 2-layer and I was planning on having both layers filled with a ground plane. Do I just connect thermal pads to the ground plane and call it a day? Wouldn't that make the components hard to solder with hot air? Do I make an isolated polygon that only acts as a thermal pad?

Speaking of soldering is even hot air the way to go in this case? My PCB has components on both sides, and I was planning on ordering stencils together with the boards and using solder paste, placing the components and then using hot air to solder the components in place. I thought a hot plate would be better but I don't have access to one and I don't know how that works with components on both sides.

I attached some photos of the PCB in Kicad, and here's the git repo. If it is of any help, I'm planning of having them manifactured by JLCPCB. It is also my first time using KiCad, so go easy on mtbox.moe/ztw2pb.png [2]: https://files.catbox.moe/hytn9j.png [3]: https://files.catbox.moe/l9nqcb.png

I work on equipment that runs off 3 phase 208V but it uses uses a transformer to drop it down to 120V for most of the controls. On this equipment I noticed that there are two fuses on the lines exclusively feeding the 208V side of the transformer and a fuse directly off of the hot side on the 120V side of the transformer.

Isn't the fuse on the 120V side of the transformer redundant? From my understanding, if there is a current spike on the 120V side of the transformer then that will cause a current spike on the 208V side of the transformer and immediately blow those fuses anyways. Is this just a certification thing where that redundancy is required? I'm in the US but this equipment does also get shipped to various overseas locations. Also, while it isn't standard, this equipment is capable of passing a TUV inspection if a customer requests it so I'm not sure if the potentially redundant fuse is just a TUV requirement.

Working on a joystick. Seems like any protocol I use to read from peripherals is going to be bottlenecked by having just one input. My microcontroller might have multiple ADCs, but there's just one processor stepping through them. Same for spi, or i2c, or uart. There's really only ever one sensor reporting back its data at a time.

I know this might not matter for measurement resolution. Especially if you're polling at like 115k serial or something, but...

That's 8 bits per axis, and three axis. Now that's at least 34 bits. To sample each axis we're down to only 4.5k samples per second. Plus whatever other cycles the controller has to handle... even if I spent half that time doing microcontrolle cycles at like 2k we're probably still well with the best star craft apms or whatever. I'd still like to find some way to really over engineer this thing.

I read a little about tdm, but that's out of my league and I don't know if you could even have 3 simultaneously signals that way

I'm thinking a microcontroller for each axis, and a usb port for each of them. So it appears like 3 different controllers to the computer. The user would just have to map the axis from the 3 controllers into 1 in their game software. I assume the steam remapping could do this.

Is it just going to get smashed back into one thread in the computer's usb hub anyway?

Any other suggestions?

I've recently bought a used computer, and it has a few problems. I'm looking for a guide to help me identify which parts are causing the problem.

I've tried to watch and read a few guides on how to build a pc, but they haven't given me any information on how to identify broken parts.

I'm interesting in a guide, but I'll also post my specific problems, if any of you know how I might fix them ^^

the problems I'm experiencing are the following:

the screen will sometimes glitch out with black areas when watching movies, but only when in fullscreen. The problem usually disappears for some time when exiting and re-entering fullscreen mode.

The computer won't run certain drivers and sometimes when powering off, the computer will use a long time closing certain applications, but will fail in the end and I have to power it off manually. Also, it will sometimes reset my settings. Back to factory wallpaper and factory everything. it remembers my users and my applications.

I've grouped them into two paragraphs, because I have an idea, that the graphical problem might be caused a bad GPU.

I have no idea, what's causing the stuff in the second paragraph 😅

also, I hope this is the right community for this question - I couldn't find any communities specifically for computers.

any help is welcomed ^^

//EDIT:

Thanks for the help :))

I removed the gpu and now only use the integrated graphics in the cpu, and the visual glitches are gone :))

I've run some tests on the computer (from the boot screen), and it seems the memory is fine. The only driver I know to be a problem is the driver for my WiFi usb. I'll try to work on that, or maybe I'll buy a WiFi card and pray that works better ^^

thanks for the help :))

//EDIT2:

All my problems are fixed now ^^

the wallpaper change was because I am a doofus and forgot that I had made a new user on the computer, which of course had the default wallpaper 😅

the driver problem was only with my WiFi adapter, and I fixed that by removing the current driver (rtl8812ub) and installing another driver (rtl8811au), which fixed the problem :))

thanks for the help :))

Hello altogether, I guess everybody has some USB-C cables lying around, but wonder if it's 3A, 5A, 3.0, TB... Anybody able to recomment a device able to determine that? Maybe also something that can be combined with a load tester.

I got these TP4056 modules from an AliExpress vendor and fail to understand how the protection circuit works or if it's just typical Ali shovelware. It could be my limited understanding of electronics.

The protection circuit appears to be just for show. To the right there's a DW01S chip that prevents over charging and discharging in combination with the 8205 dual channel MOSFET.

It looks like the drain of this MOSFET isn't connected anywhere. I've tried following the traces using a multimeter and no other pin shows continuity with the drain. Source1 is connected to Battery - and Source2 is connected to Terminal -.

I suppose the Drain starts participating in the circuit when one mosfet activates.

What was the idea behind this? That the 8205 acts as an AND gate by having them both in series?

I'm trying to make an 18650 testing circuit that uses these modules to charge and discharge a battery and wanted to use the protection circuit mosfet as a trigger for discharging.

It's an SPST-NO micro switch. Don't waste time searching for it. I already wasted mine. Just let me know what it is if you know it off the top of your head. 😊

Since MOSFETs have a gate capacitance you'd want to limit the inrush of current from the output of a microcontroller to prevent it from getting damaged prematurely. That's what gate resistors are usually good for.

Another thing is that most MOSFETs don't fully activate with a gate voltage below 10V (n type) so usually a microcontroller pin isn't good enough for switching large loads.

I have a 24V system and have made a voltage divider using two 10k resistors to step down 24V to 12V as gate driving voltage which is pulled down with a weaker MOSFET. The power MOSFET essentially ends up with a 10k gate resistor this way meaning it will take a bit longer to fully saturate.

Is too high harmful? In this situation the load is a heater that activates when the room temperature drops below 18C and deactivates when it gets above 22C so fast switching is not an issue.

I recently came to the realization that I've been kinda punishing myself with cheap no-name solder that is really difficult to work with.

I reluctantly bought this (rather expensive) lead free solder for around $25 and the difference really took me by surprise - it melts and flows so easily!

Kinda got me wondering what everyone else has been using for solder, or what's worked well for you so far at least?

I'm an EE by trade focusing on embedded devices, but most of my work is in relatively low-power STM32 applications. When I stopped following developments in hobby kits, it was mostly Arduino Unos slowly driving I2C OLED displays.

Now suddenly, there are embedded Raspberry Pis and ESP32s doing realtime facial recognition and video feeds.

Is there a good place to look to catch up on what's now possible with these embedded devices?

Also, while I enjoy the ease of the hobby kits, I'm also interested in more mass-production-focused solutions.

Trying to repair a Hyperkin Duke Xbox controller where the left trigger doesn't respond. Found that the resistance of this potentiometer doesn't change when it's moved, so I'm looking to replace it. I'm a novice with this stuff though and I'm having trouble identifying it. Any help is appreciated.

Hi everyone!

I'm trying to control a "dumb" led light strip segment with an ESP-01S. This is fairly low current, the strip will pull 150mA-200mA max (depends on... artistic? needs).

I have two NPN transistors (2N2222), one to control the 12V supply to the white "channel" and the other the red+blue (don't need the green).

I had to pull-down the gates as I had some flickering, and it works perfectly if I manually connect the GPIOs after the ESP-01S boots.

The ESP will boot if I have the RX pin (GPIO03) pulled down on boot, but not if I pull down any of the others.

I'm not smart enough to come up with a way to have that extra pin I need to be high only during boot, while the gate it's attached to needs to be pulled down...

Any thought, other than getting something with more IO pins?

I'm learning about electronic components. I believe this is the part which has broken and made this heating pad unsafe to use. Well, unusable, not just unsafe lol.

I'm planning to make a modular synth from scratch, but I need to start with the PSU. Do you see any issues with this schematic?

The main difference between this design and traditional linear PSUs is the replacement of the transformer/rectifier/filter circuit by Mean Well IRM AC/DC converters. The linear regulation circuit is basically the reference design for the 78xx/79xx.

Do you think there would be an issue once scaled? The AC/DC converters have a lot of headroom, as I plan to make up to 3 regulation circuits like so:

(the regulated outputs will actually never go nowhere near 1A per rail)

cross-posted from: https://lemmy.world/post/9052986

I've got an antique lamp that needs a new switch knob, but then scope-creep happened and now I want to "smartify" it. I started off thinking that, since it has a metal body, I'd install a capacitive touch switch, but now it's escalated to wanting to put an ESP8266 or ESP32 in it to handle the capacitive sensing, Home Assistant connectivity/control, and maybe even switching to some kind of low-voltage RGBW LED instead of a 120VAC Edison-base bulb (especially since I suspect I'd need some kind of antenna sticking out the top, since the metal lamp body would presumably otherwise block the ESP32's signal).

The lamp, BTW:

(Apparently it's a Genie lamp by Laurel Lamp Company, in case anybody cares. Also, the lamp shown is the same model, but it's not my picture.)

I'm aware that the "easy" way would probably be to just screw a smart light bulb into the socket and wiring I already have, but (a) I'm picky about both avoiding "clouds" and using FOSS firmware, and I don't feel like sorting through the junk on Amazon to figure out which ones can be flashed with ESPHome, and more practically (b) that wouldn't let me turn it on and off just by touching the lamp body, which is what sent me down this rabbit-hole in the first place.

Anyway, I know this sort of thing can be done, but I'm not completely sure how. I know I could figure it out myself eventually, but I figured it couldn't hurt to ask for advice in case somebody happens to be able to rattle off part numbers for the whole BOM off the top of their head, or knows exactly the right ESPHome howto to point me towards, or something like that. Any advice is welcome!

(In case it's relevant: my level of experience is that I programmed an Arduino to run neopixels (WS2812 RGB addressable LEDs) once, I've flashed ESPHome on some Sonoff S31 smart switches, and I'm a software engineer by trade but have never worked on anything IoT related professionally.)

I want to replace one half of this with longer wire, but I am not confident about the name of the connector used.

Image of JST-XH included to convey size. Ruler is metric.

So, there are these great 32700 LiFePO4 batteries that showed up in my local industrial market. For like USD 2$!

However, there are no LiFePO4 chargers available. The vendors assure me I can "totally use" a 4.2V Li-ion charger, but I don't believe them (although the cells test as being in good shape).

I whipped up a 5V system with a buck converter managed by an MCU. It turns off the buck converter that charges the battery, measures the battery voltage, and if it's under 3.6V it enables the buck converter. Repeats every few 100s of milliseconds.

Did I overengineer this? Could I have just used a linear voltage regulator that outputs 3.6V (or a Zener), and a current-limited 5v power supply?

Charge speed is not really important in my application. Anything under 4 hours is great. Frankly, I'm just trying to phase out the less safe kinds of lithium cell in my lab.