I’m trying to better understand how to read electrical schematics, and there is something that has always confused me. If electrons are negatively charged and therefore move from the negative terminal toward the positive terminal, why do we still use the convention that current flows from positive to negative?

I understand that this is the conventional direction of current, but doesn’t this convention make it more difficult to understand what is actually happening in a circuit, especially when looking at a schematic?

For example, when I look at an electrical circuit, I often have trouble following the path of the current and understanding how the different components behave. It sometimes seems strange to think that the current “reaches” one component before another, because in a schematic several components may appear to be connected at different points without there being an obvious sequence.

So I would like to understand three things

1. Why was the conventional current direction defined from + to −, even though electrons move from − to +?

2. What is the practical relationship between electron flow and conventional current?

3. Most importantly, how should I read an electrical schematic so that I can understand how current flows through the circuit and how the individual components interact?

I’m particularly interested in understanding the physical meaning behind the schematic, rather than simply memorizing the conventional direction of current.

I dropped my GPS RTK receiver and ripped off the antenna connector and its solder pads too. Is this salvageable? I did try to expose the trace and solder onto that but I’ve been unsuccessful

If a relay is switching a high-current load, its contacts can eventually weld together due to inrush current or a fault.

If that happens, the load may stay ON even when the controller says OFF.

How do commercial products handle this? Do they use two relays in series for redundancy, feedback, or some other fail-safe method?

Basically the title! No wires connect the switches to the board, but there are clearly magnets. Thanks!!

I tried to create sine waves using DDS and 8 bit R-2R DAC. The output waveform is like this instead of a sine wave is there anything I'm missing here?

Dear Redditors,

I have an electronics project with my laptop, that I could use advice on regarding use of buck converters.

For power, I will be tapping into the 11V 10A circuit for the secondary battery (that I don't use), which also has a fuse.

The project will involve adding some 5V usb ports, an LED that uses 3.7V and minimal amperage, and additional 3.3V power for a second port.

Looking around aliexpress, some buck converters have a variable output that is dialed in with a potentiometer. Others have fixed output voltage.

Is it better to use one or the other? Do the converters that say "5V" really put out 5V, or can you achieve this better with a variable output converter?

For amperage, is there a certain margin above the needed amperage that I should shoot for? One is that I question how well these converters can achieve the amperage they advertise. The other is that I want to minimize heat.

I had heard that a converter rated at 8A will stay cooler, last longer, and provide more stable power when powering a 5A device, than a converter rated only at 5A. They may though use more power, or there may be other disadvantages.

I appreciate the input!

I'm making a random number generator based on white noise sampling for a side project, and I'm looking for some feedback on what I've drawn up for noise amplification, filtering and sampling. The ADC will be sampling with a relatively low sampling rate (<100Sa/s). Large bit number integers (16 - 256 bit) will be compiled from multiple 8-bit samples. The parts selection is mostly what I already have on hand, LM2767 charge pump being the only thing I'd need to order. I haven't used charge pumps before, and the application notes in the datasheet are frustratingly vague in terms of capacitor selection, I'd love to hear some tips and pointers on that.

there is a photo as the where I think the traces go but what do I do after I glue the MOFSET back on

I soldered a piece of wire to an RF transmiter, due to skill issue, solder got to other pins, but I managed to pull it, rn there doesn't seem to be any solder iron connected to other bits other than the antenna, but the area around the antenna is sparkly.

(PCB also got quite hot when soldering)

Hi, absolute beginner here!

I need to make a simple circuit with 6 LEDs and a little push button for a free-time project and have trouble finding out what resistors I require - because the website I bought the LEDs from lists 2 different values for voltage on the product page.

"Forward voltage: 3V

13V"

I'm only assuming it's the min. - max. value? But I need a specific number to calculate the resistor value.

Thanks in advance.

I'm using an rc522 rfid module, I have the right rfid cards so that's not the problem

I used it with and esp32 so there shouldn't be any 3.3v signals problems

Here's the pinout I used to connect it to the esp32

GND: GND

RST: GPIO 27

SDA (SS): GPIO 5

SCK: GPIO 18

MISO: GPIO 19

MOSI: GPIO 23

I'm losing my mind over this, I switched to a breadboard as I try to find out what's wrong and it just doesn't work now at all.

My esp32 bare is fine but when I put in the breadboard or the perfboard I made it keeps constantly resetting when I look at serial Monitor.

Rfid module wokred kind if on the perfboard, it would constantly break

on the breadboard it didn't work at all

People in the live sound engineering community say trying to add distortion to a microphone makes it so much more prone to feedback. But why is this the case?

Here's what I understand so far (correct me on anything if I'm wrong):

Feedback occurs when the gain around the loop is greater than 1 because then any sound that goes around becomes bigger with each round trip. There's also criteria on the phase shift being 0º round trip, though I'm pretty sure but I think all that does is select which frequencies get amplified vs attenuated (which is why feedback tends to become a pure tone). Since the speaker system has huge headroom, the self-amplifying sound can reach deafening levels well before the PA system saturates.

Eliminating feedback boils down to getting the loop gain to be below 1. You can do this is by messing with the environment so this gain falls below 1 (e.g. move the mics away from the speakers, turn the speakers so they are pointed away from mics, adjust the levels of the speakers, etc).

Assuming my understanding correct, I'm confused on why adding distortion would make this process worse.

Distortion involves clipping the top/bottom of a waveform (in the extreme case, sine waves become square waves). The easiest way to do this is by increasing the gain of a signal so that it hits the rails of the circuit, e.g. V+ and V- of an op amp. If you do that, the gain of this op amp could combine with the gain of the rest of the system and tip the full loop gain to be over 1, which would then cause feedback.

But suppose you apply a gain of G to a microphone signal to get it to clip, and then you apply a gain of 1/G so that you have a net gain of 1. Then, since the gain of the rest of the loop was below 1 (because you set the environment up that way), it will remain so even after the signal has been clipped.

Is there a flaw in this technique that makes it not work?

Hello, everyone! I assembled a D2-5 line-following car, but it keeps moving straight even when there is no black line. Both motors remain on, and the car does not respond. I tested the R14 photoresistor with a multimeter, and its resistance changes depending on the light, so I believe the sensor is working. Does anyone know what could be causing this problem? I am still a beginner in electronics, so I would appreciate simple explanations. I can send photos of the board and the solder joints if necessary.

Building a DIY VR glove with force feedback. Looking for small servos that can report finger position and also push back with controlled force. Is something like the Feetech SCS0009/STS3032 the best option, or is there something better? Using an ESP32-S3.

I'm actively working to become an electronic lab technician. I've been a hobbyist since starting my lighting technician career. I'm currently investing in some gear for PCB repair (motherboards and laptop repair). if I were to start getting into this hobby a year or two ago the prices would be for hobbyist but now the cost of everything has doubled from DMM and sbc's that you kinda have to take it seriously. I would love to get a eevblog BC 235 or UNI-T but I'm curious what handled DMM are you using? If you have data logging and stuff like that is that kinda like the car in the garage you never drive? thank you hope that makes sense.

I wanted to solder them better and did this.

Can I fix this thing somehow or is it damaged for good?

All of those points should be individual.
Sorry for bad english.

Hi! I’m creating a new post since this subreddit doesnt allow for reposts.

My Vox AC30C2 tube amp shorted out and exploded some pcb insulation off between the flat metal connector (J29), which runs about 300V in normal operation, and the adjacent tracer, wich is very low voltage and leads to the blue R81 resistor.

What would be the best course of action for the arching gap? Should drill it or fill with some insulation material etc?

Also feel free to express emotions regarding the high iq pcb design of putting those two circuits so close together.

I'm trying to understand how a transmitter and receiver can stay synchronized.

My first thought was to use accurate time on both sides and generate a known pseudo-random sequence or code based on the time. But if the receiver's clock is slightly wrong, the synchronization could eventually fail.

So instead, can the received signal itself be used as the reference?

For example, could the transmitter send a known preamble, sync pattern, pilot signal, or pseudo-random sequence, and the receiver detect/correlate it to determine exactly where it is in the sequence?

What are the common techniques used in real communication systems for this? And when would you use signal-based synchronization instead of time-based synchronization?

I believe I have solved the problem but the answer listed seems to be much more compact and I’m not sure how to get from my answer to the one listed in the book. If someone could check my answer and let me know how the one in the book was derived that would be greatly appreciated!
If there is a better community to post this in please let me know!

For those it concerns: Open Course Ware (the place I am getting the questions from) is a free online course for learning, not obtaining a degree. It’s not a class in the traditional sense as the lectures are simply videos recorded in 2007 and free text books. I have no peers or instructors to ask for help when I can’t solve a problem. I’m not looking for answers to homework but rather aid in learning and mentorship.

so i made a setup with light turning on/off from my website with pico W + relay modules. i connect the light on the NO. it works fine on the wokwi simulator it worked fine for first few minutes as well. but then the light of some relay modues keep being on regardless of the signal being sent from pico. even if i turn off power for pico the lights keep being on on other relays except one. one moule works fine tho.

i've tried on 2 channel and 4 channel relay and on both case one relay keeps working fine an other doesn't. the other light in relay keeps being on. I need some help.

So I picked up a Samsung FlexDuo Range Oven combo. Was told it was a heating Element Issue. Repaired and cleaned connectors, although one seems to have higher resistance than Samsungs desired range.

During testing, interactive display felt loosely responsive. I had to really focus on press location, to make sure I gently pressed in the right spot, but I am not familiar with the interactive display or this oven in particular so I don't know if I could not press some keys because of the order of operations ignoring it or if they just weren't working. Eventually it all started to cut out.

The testing of the oven, separate from range controls, started with bake feature. I got up to 455 F. Tried to crank it up higher but that was the limit. Thermostat was interactive but made audible clicking sound once clicking of the best coil inside thermostat (I believe) measured and returned to heating, or maybe it was open / control gateways, but there was an audible click. That seemed louder than I think it probably should have. But it seemed regulated. I turned on convection bake option once I gave up on gaining past 455 F temperature. Original owner said normal bake option of the oven was defective, it was taking forever to reach only 300 f but not above. The connectors to the element had over heating damage and warped. Or overheated because poor application. Howver the blade end / element end did not appear to have even gotten hot at all beyond some gentle cleaning with brass brush.

Internet says the ribbon cable is a common failure point on this. I noticed glass was not seated well into frame so gently cleaned with alcohol and it's still not seated great. Glass looks wavy but could possibly not be the actual problem. I am going to dry out with heat gun and get back at it.

I'm not sure if you guys could point out likely failure locations or anything that looks suspicious, but ut would help a lot. I'm just a hobbyist. I didn't see any failure or over heating indicators on this or the main power supply board or other components.

One thing I noticed when 455 on convection was fan running at beginning but turned off and on and neither fan in within the oven related to convection were spinning. I let it cool and set desired temp and they still did not spin.

I've heard cleaning grease off thermostat is an effective treatment but haven't gotten that far. They did mention installing a new thermostat control did not work. All screws there were loose when I checked to see if everything was snug. Is it important that CN1 1 3-PIN on user interface board doesn't

Control board DG94-00702A

This may be a stretch without an obvious / simple visible error, but I wager others have been here before and might have some tips.

I've been trying to build this crossfader circuit, which has a zero-crossing detection bit that should cut the audio cleanly and without a "click." The intended use case is a sharp cut for "scratch" DJs, just one turntable or audio source on one side of the crossfader as I understand. The author's site just started having technical issues (and I have emailed them), but the web archive has a snapshot here with the schematic and some details.

I started this with tidier wiring intentions, I swear. ;) Having a proper full-size breadboard would save some wiring, in retrospect.

The circuit is somewhat working. I suspect some signal is bleeding into the audio output and it's got a nasty audible click when audio goes in/out. I realized the schematic didn't specify VCC/VSS for the TL074, 4013 and 4066 ICs, and I checked for additional floating pins. Voltage wasn't specified, but it looks like 9-12V is within spec for the ICs?

I had some 50nF ceramic on the signal input, seemed like an aggressive high-pass filter on the sound. Not sure if I chose incorrectly, or what.

I am not an electronics engineer by trade, but I have an appreciation. This has all been an experiment, for fun.

I need to get a couple mA of current at 5vdc from a 48v phantom powered mic input. I was planning to use a couple diodes to combine the DC power from pins 2 and 3 and send that into a LDO. Is it this simple? Is a cap needed to block dc from the audio output from the device?

I can't find a schematic, every schematic I find is for making a 48v phantom supply. I am trying to do the opposite.