r/AskElectronics

Please help me. This RF counter is my moat favorite tool 😞😞

I bought a cheap soldering iron, and after about 10 seconds of plugging it in, it started producing fumes and the tip turned yellow. When I tested it, it didn’t melt the solder at all.

I looked it up and saw that some fumes can be normal the first time due to factory coating burning off. So I unplugged it, then plugged it back in again and waited about 2 minutes.

But it started producing fumes again, and the color got really dark (brown) but this time it could barely melt the solder(still really weak). Is this normal? Am I just stupid?

I lost a similar charger to this (pic from google), and I don’t know what this is called, nor do I know what are the alternatives that I can use in place of this…

I teared down the Xiaomi light bar connector because I wanted to repurpose the light for ambient background lighting. But the cables would dangle out ugly, so I'm thinking about buying something else to make it clean. Any ideas?

the idea is smpc keeps the load ON and charges the lithium-ion(edited: cuz forgot to mention what battery) battery simultaneously, when smpc is OFF battery drives the load so that the load never turns OFF.

is there any drawbacks in this circuit, does the current from smpc heat the battery more???

I wanted to learn more about circuit boards but youtube tutorials or lessons are too complicated and I literally can’t keep up with the terminologies and just the overall lesson. I thought that maybe seeing one myself can help me grasp the concept of how it works and why it works so in a whim, I took apart my old phone. I’m not sure if this is even usable haha. Help would be much appreciated. Is this even a circuit board?? Im losing my mind

From a Waveshare 1.8" touchscreen knob.

These switches are triggered both forward and backward when the knob is spun. the silver body is 5mm across. Upon searching I always end up with either a rotary encoder or a 3-way rocker switch.

Thanks for your time!

Hello everyone, i will start designing an audio amplifier pcb that uses the mh-m18 bluetooth module and tpa3116d amplifier. It will be powered by a 24v external supply (smps probably wall adapter). Searching online led me to the 2 examples below. Which one is optimal to eliminate high frequency noise from getting to the amplifier

I have harvested this track pad from a gaming laptop(asus tuf f15) and I want to use this as a external track pad but when I see the conversion guide on YouTube they find the test pads and soldering it to a Arduino to convert ps2 to usb but the problem for me is that I can't find the data sheet or the pinout for this trackpad can you guys please help me make this into a usb trackpad

The writing on the chip

Elan

33221B-3B00

2109 BG21251

During installation of a TMR stick I accidentally damaged C25. Testing the controller the stick registers as being stuck at the top, horizontal movement works fine, just vertical movement isn’t working. How should I go about this? I am not very skilled in micro soldering so my confidence is low to solder a new one on.

These are on a DCDC converter board

the clock runs fine for a moment, but then suddenly stops and freezes. i've opened it up and all the wiring seems to be in order. it seems to be an old DIY project. anyone got tips?

Hi all, I’ve got a PCB with an existing transformer designed for only 100V input and would like to replace it with a part designed for 230V operation.

The issue is, it obviously needs to fit the existing PCB layout and size. Specs of the transformer should be: 230V in/~14V out/ ~2.0 VA

Physical dimensions are around 35x30mm

Pins on the primary side are 2 for the input 15mm apart and 3/4 on the secondary side 5mm apart each.

Both arrays have a pitch of 22.5mm apart.

Now this is incredibly specific, and so far I can’t seem to come up with anything that would fit. How would I go about finding a matching transformer?

Spent the past couple of weeks rebuilding the schematic of a 0-10V / 0-1.5A lab bench supply. Input is USB-PD 15V, with a buck pre-regulator (undecided model yet) tracking Vout + 1.6V headroom feeding a linear post-regulator with a PNP pass element (MJD32CT4) and NPN driver (BCP56).

The control architecture uses a diode-OR (BAT54) minimum selector for seamless CC/CV transitions, with separate Type II compensators for each loop. The error amplifier is a discrete differential pair (BCM847BS matched NPN) with a negative rail, and a slow OPAx322 outer integrator for DC accuracy - a 2DOF approach to avoid integrator windup injecting into the tail of the diff amplifier.

Done a Bode plot stability analysis on both loops, across the whole range.

CV loop: 70 kHz crossover, 71° phase margin

CC loop: 59 kHz crossover, 48° phase margin

Both loops swept across operating points (0-10V, 0-1.5A). Known degradation at near-zero setpoints. Is that fine? Unsure of that too.

Finally, I've attached the injection points for the cc and CV loops. I'm unsure if they're correct for this setup. During each test I've detached the bat54 anode of the other loop to prevent it from fighting the other loop.

Happy to get some feedback.

Image labels:

1 - Simulation schematic

2 - CV plot

3 - CV injection point

4 - CC plot

5 - CC injection point

how does it work?

the core is in 2 parts.

how dangerous is it?

what can I use the transformer for? bcuz no intention of repairing this.