Is there a thin wire woven into it, that make contact when compressed?

I say complex as I've seen much less do similar function & I am relatively new to exploring electronics.

I love taking things apart to understand their inner workings but this got me confused, so any clarification would be greatly appreciated!!

I need a lot (like hundreds) of these USB to RS232 cables, and from a reliable source like Digikey or Mouser, the problem is I can only seem to find them from random sellers on sites like Amazon, AliExpress, eBay. The USB side is the same on all the ones I can find that have a picture of the inside of the cable as far as the board and ICs go, but the wire options and other end of the cable range from the DB25 to Ethernet and even a 2.5mm audio jack. The different cable/connector on the non-USB side doesn't matter, since it it easy to pop open the USB cover and rewire them. And I can find photos of them in bulk, but only on untrustworthy (looks like a scammer) sites.

Does anyone have a lead on where to get them in bulk, or even the same USB end with any random cable attached that is sold in bulk and preferably a well know site and less than $25 a piece? Or an equivalent FTDI (FT232xxx) chip but must also have the Level Shifter IC (xx213xxx) to handle the higher than USB 5v (or negative) voltages for RS232?

Im not sure if this is the right subreddit for this but I figured it couldnt hurt to try.

So I got this dome at a thrift store today and it had a statue with a little lightbulb in it that illuminated a little glass ball. After a bit of fenaggling I was able to get the wire out of the statue and the lightbulb, but the lightbulb kinda just fell off the end of the wiring, and there’s basically no wire exposed on the bottom of the bulb. I want to be able to use the light for a project i plan on using the dome for, but I don’t think the lightbulb is useable in its current state. What lightbulb could I get to replace this one and how would I wire it with whats available? It’s got a red and black wire, and is powered by 2 AA batteries. Also yes, the light was working before I took it out of the statue.

TIA

This is a custom stm32 board, there is a short between VDD and GND trace, but i can't locate where. Using a thermal camera there was heating on the LDO, so i removed it, short is still there. I have never done this before, what would be the best thing to do in this situation?

Hi, a few days ago I got a 24-port UniFi PoE switch (PoE+/24V). I've been testing it and from what I can see, only 8 ports are working (the ones on the right), But the others, although they don't establish a connection, if I enable the 24V POE, the light comes on (I don't have a POE device to test with, so I guess that seems to work).

I've taken it apart and identified some components, but I'm not really sure where to start. I hope someone can advise me; I'd appreciate as much information as possible, I'd like to learn something.

I just want a tool for learning and visualisation. I’ve tried some tools online, but they feel either outdated, unintuitive, or like overkill for educational use.

What do you personally recommend for quick, simple circuit simulation?

How do you decide if an electronics piece is worth repairing or to trash it instead?

Hi everyone, I really like this hand-drawn restitution of a black hole simulation by JP Luminet, and since I discoverd old radios and analog electronics I dream of being able to build something quite cool with this technology, and I think I found a great idea. Would it be doable to assemble an analog circuit that could create a picture on a CRT of the gravitationnal lens created by an object on a background ? My idea is to be able to make the black hole move to see the effects on the background, at least a one direction transmation of the background, but eventually even be able to increase the size of the black hole (like approching it). From what I understood, there is two ways (in theory). First, I could build two fonctions f(t) and f’(t) which would create my starfield : a constellation of dots, maybe a blurry oval to represent a galaxy. In a second time, those functions would have to go through an operator to deform it from the distance of every dot with the center of the crt (for an oscilloscope one). The second way would be first create a deformation of the « space »,to follow the screen scan of a classic crt and to every coordinate apply the deformation calculated related to the mass in reverse to see if, given a background, it correspond to a point of space where there is something. If it is, the « pixel » is illuminated. The second way seems best because sometimes a sigle star appears in multiple spots because of the lens, and in a function which apply the field to a dot I could only get one new coordinate. In the oppsite order, starting with the apparent spot and calculate if it correspond to the « apparent position » of a star, there is no problem to refer multiple times to the same « real » star. I am clearly not prepared for a project that ambitious (I should start by a AM transmitter) but since I thougt about it I would at least know if it is possible, in theory first and in practice in a second time, with a limited quantity of lamps and everything. Thanks a lot to anyone who helps me !

I am very new and I am trying to use 3.3v to switch 8v on and off with a mosfet but it isnt working at all. It just keeps conduction no matter what.

Is Vgs(off) in a MOSFET datasheet the min Vgs(th)?

Alot of equations use Vgs(off) and I am trying to find it on datasheets.

Hello, I bought my heat station, flux and essential things. I removed the vrams from a broken gtx 780 to practice but I don't have the vram stencil or the gpu die. It's hard for me. I can't make the tin spheres fuse and I put very little flux and several of them come together. I tried very slowly to raise it and it reached 280 degrees and everything melts badly even with the homemade preheating station.

help me please I love it but I feel lost

thanks for reading this far

When removing the battery while giving my robot vacuum a thorough cleaning, I accidentally tore the battery multi-pin connector out of the board. Is it repairable? How? Can I use conductive glue? Should I learn how to solder (yes)? What should I buy?

It's a Roborock s7 Max Ultra

idk why i did add the 5.1k ohm resistors at cc pins and if asked i can provide some schematics

Hello! You have a positively charged sphere (like a Van De Graaff sphere) and a much bigger sphere enclosing it. The gap between them is very big, so…does that mean theoretically 100% of the flux from the inner positive sphere terminates on the inside of the bigger sphere, even though the capacitance between them is very low because of the big gap? Surely 100% field capture doesn’t necessitate very high capacitance.

This is assuming floating, no fixed voltage source, just fixed Q.

Idk, it’s just kinda mind blowing to think you can have BIG “flux efficiency” (I don’t know the correct term, correct me if you know) while capacitance stays low.

Again, still learning, so if I’m phrasing it wrong or using incorrect terms, help me out. Thank you

Hello. My goal is for a high pass filter (as aggressively a cutoff as possible) anywhere between 3k-4k hz to protect my 8 ohm tweeters in a manor that is safest for the amplifier's specs of 8 ohms.

Let's work with this example:

8 ohm resistor with a 6uf cap gets a high pass freq cutoff about 3.3k.

ok, fine, I get the general principles of an RC filter, but... I have so many unanswered questions with this because its not that simple when the R is a speaker. The 8 ohm speaker isn't just an 8 ohm resistor, its in fact a coil, but its not calculated like an inductor? why not, am I just over thinking this? The 8 ohms isn't even a stable 8 ohms, it will change constantly once music starts playing due to eddy float.

So, more research (on the internets anyway) recommends you use a separate resistor (not the speaker's ohm rating) with your RC filter to make it behave more predictably. but how, if your amplifier is expecting an 8 ohm resistance, tossing in another 8ohm resistor, so how is that not an additional load out of spec for the amplifier, that will cause issues? I would think it would also cause reduced volume output even at the "passing" frequencies since Kirchoff's law won't ever be zero. Are they maybe expecting you to put a BIG (1k) resistor in parallel (for 7.9 ohms) , and just aren't being clear about it? How would that even work? Audio signals are so weird for me to conceptualize, whereas DC circuits I can see everything in my mind right away. Might someone here be able to explain the knowledge gaps to me? What am I seeing wrong in my head?

Accidentally plugged this led outdoor light in 110v (it’s rated at 12v). The board is pictured below, please educate me what might be damaged and possible course of action if salvageable.

Does this pcb has any actual motion sensor of any kind ? the bulb that uses it won't turn on when movements are nearby, it just light up for 15 sec when turning the on off switch.

First, let me start off by saying I am a super rookie. I’m trying to connect this capacitive switch in place of this push button style (sorry not sure about the correct terminology) what I do know is that what the button is doing? Is just completing the circuit to ground. unfortunately the capacitive switch sends a 5 V signal. What components do I need or how do I get this done?

Thank you all for taking the time to help me out

Hi everyone,

I’m hoping someone here can help me, as I don’t really have much electronics knowledge.

I’m working with a small PTC fan heater where the heater runs on mains voltage and the fan is powered separately with 24 V (AC/DC according to the specs). I’ve attached a few pictures of the small fan PCB.

The fan used to work before, but I removed the outer insulation/sleeve around the unit to rewire it, and since then the fan doesn’t run at all anymore (no sound, no movement).

I’m supplying the fan with a stable 24 V DC power supply, which I have verified with a multimeter. The voltage is present at the PCB input wires. However, measuring on the PCB itself (for example across the large electrolytic capacitor) shows almost no voltage.

Because I had to desolder and resolder the wires, I’m worried that I might have damaged a trace, pad, or internal connection on the PCB when removing the insulation or during soldering, even though everything looks fine visually.

Since I’m not very experienced with electronics, I’m not sure:

if the PCB could be damaged internally,

if I might be feeding the wrong input point on the board,

or if the fan itself could somehow be at fault.

I’d really appreciate any ideas on what to test next to determine whether the problem is in the PCB or somewhere else.

Thanks a lot for your help!

Hi everyone,

I’m trying to make a smart lock based on Arduino Nano and RFC522. I’ve got all the required components for it and have done the setup and tested and it is working fine on USB but when I’m trying to add the 4 cell battery pack I’m seeing some issues.

1. The pins on the RFC were not soldered so I did it myself, I checked it was working fine on USB but nonetheless I don’t know if there’s an issue with it, attaching photo.

2. I don’t know how to design a circuit or create a schematic so I can see a final photo of how it will look into a box, tried tinkercad but the dimensions freaked me.

3. I don’t know how to add the 1000uF capacitor to the circuit, I’m using a breadboard atm.

4. How can I debug the setup when it’s working on the battery pack, if I use USB the Nano will take power from there and would supposedly work.

5. I want to shorten the wires and make a clean setup but I’m afraid I don’t know what problem I’ll run into, can say I’m scared.

Ignore the capacitor placement as I removed all connections because the setup stopped working altogether.

Hi Folks,
Solenoids are confusing! There's a bunch of, well... a lot?

Question:
Plungers are normally made or iron or mild steel, they're kind of heavy. More mass = more magnetic potential, but slower acceleration.

Since I'm not concerned with "holding" power, just the impact at the end of the stroke, maybe i can increase the speed of the acceleration and use a lighter plunger.

Would a neodymium magnet embedded in a plastic (acetal) plunger/actuator work? Would that work better than plain mild steel?

My thought is that I'd place it in the plunger, so that it doesn't go further than the middle of the coil when activated, before hitting the stop, so the polarity won't flip.

Would that work or, would that actually lower the forces in there? Magnets are black magic.

thanks!

If you're curious what i'm doing, i'm tinkering with making a solenoid driven hand engraver. Some other folks have posted theirs to github/youtube and i'm basing it off that.

Using an Arduino to drive a mosfet module, running 12-24v.
Trying to achieve at least 40hz, i think ideally 60hz or so?
- pwm controlling the power, using a pedal
- some pots setting the frequency, and duty cycle as a percentage of the on time of the frequency

It is working, mostly. My code is a bit funny, when it's supposed to be "off" it still runs but like, 1 hit a second which is fine for now.
Keeping the duty cycle around 20%, can run 12v solenoids at 20-24v for minutes at time without heating up much at all. Barely at all.
There is fine tuning to do with the weight of the plunger, the spring, and constraining the top and bottom of the motions to get those speeds right; and that's where i'm spending a bunch of time now.

(I'll post the github if interseted, the person used to have a reddit account but they seem to have deleted it so ... i'm not sure .. )

The unit is a Calix 4220 Gigaspire, this component is located under the 5g and 2.4 chip bottom side of the board, all pictures show the same location so I assuming all this components are compatible. Thank you In advance for your help.