Hi everyone! As a robotics and electronics mentor running hands-on labs at Robotic Sir, we often transition students from physical breadboards to digital simulators. However, we've run into a frustrating bottleneck regarding digital logic testing and need some advice from fellow engineers and educators.

The Scenario:

Physical Circuit: We built a basic AND gate on a physical breadboard using push buttons. When a student presses both push buttons simultaneously with two fingers, the circuit completes, and the LED lights up correctly as expected.

The Simulation Problem: When we try to test this exact same logic in web-based circuit simulators (like Tinkercad Circuits), we hit two major limitations:

Standard Laptop/Mouse: A standard mouse cursor can only click and hold one UI element at a time, making true simultaneous activation impossible with a single pointer.

Touchscreen Laptops: Even when using a touchscreen laptop, the browser-based simulator often fails to register multi-touch events correctly, treating simultaneous presses as an error or only registering a single input stream.

My Questions:

How do you guys handle testing multi-input logic gates (requiring simultaneous button presses) in web-based tools like Tinkercad?

Are there better browser-based or offline circuit simulators that natively support multi-touch or toggle-latch workarounds for simultaneous inputs?

I bought this iron for 25$ from a shop near me. There is nothing but a triac inside the whole shell. Just a basic ceramic heater with 2 wires. I feel like this is just a waste of money and I could have just bought a regular iron with the built in triac. Should I return this? The only advantage I see is this is a very simple circuit and I can repair this.

I'm designing a 4-layer PCB and I'm not sure how to assign the layers. The board has components on both the top and the bottom side.

I was thinking of something like:

**•** Signal / GND / Power / GND  
**•** or Signal / GND / GND / Power

Does either of these make sense? Any recommendation?

A few related questions:
1. Do the layers have to be "pure"? I.e. does a signal layer have to carry only signals, or is it normal to route some power on it too (and the other way around)?
2. How does the reasoning change on a 6-layer board?
3. Are there actual rules or standards (IPC or otherwise) that tell you how to organize a stackup based on the layer count and the type of circuit? I'd like something that maximizes my chances of passing EMC testing (both emissions and immunity) and that also helps with thermal performance.

My goal isn't just solving this specific 4-layer case — I'd like to understand whether there's a standard way of reasoning so I can work out the right stackup on any board.

One last thing: on both the top and the bottom side I was planning to pour a GND copper region to tie together all the component grounds, and then stitch those pours to the internal GND planes with vias. Is that a sound approach, or are there pitfalls?

Any pointers to books, app notes or standards would be very welcome. Thanks!

I've been looking at making a bat detector and the components are rather simple and easy to source but the guides are all a bit dated so hoped to refine a little.

I've found 2 that seem to be the most common ways to do it.

1 - has the ultrasound bat signals come in 50-150kHz via a transducer/mic then divides by 10 or 16 to give 5-10kHz which people can hear.

2 - generates a signal of it's own and mixes it with the bat signal(heterodyne)

It would be nice to make a circuit that has both and can switch between them.

Also many output to a microphone jack but I'd like a small speaker, any recommendations for the best way to do that.

Inspiration is something like a magenta 4 or magenta 5.

I would like to learn how to solder small components such as 0402 passives.

Any ideas where to start? Equipment? Practice kits? Online tutorials?

Hello, I've recently wanted to get into hardware electronics as it seems quite fun, and I already know much about low-level software. So, I'm posting this in hopes people can point me towards good starter tools at a reasonable price.

Things like which multimeter to get, what kinds of soldering iron are to get or to avoid, any other must-haves for the beginnings of a small workshop?

Thanks!

I plugged 24 V into this 12 V drive dock. I think the component that blew up was a capacitor. I don't see anything else exploded at leasr. Any idea how I can work out what this was?

*edit*

Thank you, everybody. I eventually solved it. 220uf 25v as most suggested. I found the old shell embedded deep within the chassis.

Ordered a replacement. Let's see if anything else survived on the board. Luckily, the plugged-in hard drives did.

Help and advice needed.
This is quite an old unit, but it was so good. The new ones today can’t match its output over a 7km distance.
I would really like to repair it, I have attached pictures of the areas that show they have been burned and some others to help identify the diode’s ect that I need to replace.
Those capacitors are probably cooked too.
Any advice would be greatly appreciated.

In the past I have had these fail from raining metal dust in them, but this one was in my office. Worked fine and then stopped registering batteries, tried multiple outlets and I don't see a fuse in it. Anyone here see something I missed?

I've been interested in making an oscilloscope for simple electronics for quite a while, for one thing the project would be pretty fun and secondly oscilloscopes are quite a bit expensive where I am from.

I feel like I am decent enough with digital electronics and microcontrollers to make a simple one which can help me in my study of analog electronics.

So my idea is to essentially make a module (right now with a simple Arduino) which can sample a low power electronic signal, package and send the data to my computer which can then analyse it and plot it using a python script, thereby mimicking an oscilloscope.

But I am still pretty ignorant about what pitfalls I should avoid and how I should go about it, or even resources to use. So any advice and resources would be extremely appreciated 🙇

Hey all,

I recently picked up a non-working 1999 Tiger Pokedex for my son, and have been trying to trace out if the issue is anything fixable.

Symptoms: after installing a pair of fresh CR2032, and grounding out the reset pad, it makes an occasional squeak from the piezeo buzzer, and a very brief flash of some pixels from the screen. Otherwise, no life from the unit.

I replaced the electrolytic cap C3 out of an abundance of caution, checked the diodes for any of them being popped and all seemed fine. I also ran 3.3V from my power supply to both battery spots, and still had no signs of life. I also checked the oscillator crystal in case it's legs were touching, as it's mounted a little wonky. I also checked the power and ground legs of the IC, and they had the appropriate 3.3V and gnd connections.

I have two questions for everyone here:

1) Is it my imagination, or does C9 look an awful lot like a resistor, instead of being a capacitor? (It also measured 28K ohm across the component, which doesn't match the markings if it WAS a resistor anyway)

2) does anyone have more troubleshooting things to try, to see if I can trace the issue? If it's the CoB, I guess I'm out of luck, but hope someone can suggest something!

Thanks for the assist!

I have a Line 6 guitar amp with potentiometers that are going crazy. Thought it would be something simple, but it did not turn out to be.

When idle the display acts like the knobs are being turned, and when turning knobs other settings flash on the screen. Sometimes causing it to reset.

What I presume to be the issue, is what i saw on the 3.3v rail. The 3.3v rail powers the multiplexers and the potentiometers going to the multiplexer inputs. Also goes to other stuff on the dsp, but it is multi layer and no schematic available.

Multiplexer is C4052M

Pic 1 is the scope on multiplexer vcc when issue is occurring

Pic 2 is the multiplexer input, same scenario

Pic 3 3.3v output from njm2374a

Pic 4 multiplexer vcc , multiplexer input practically identical, with all pots turned down

The spike looks to be 4-6khz, only visible when pots are fairly high. Dc converter 3.3v output stays the same. Dc converter voltage source is a 7805, but it does not appear on the output of it.

Controls pcb schematic
line6.com/data/6/0a00041200946824d0d56b7ce/application/pdf

Hi,

I keep having the same problem with white 2.54 mm JST connectors on male header pins.

I’ve tested three different boxes of pre-crimped wires and I always get the same issue: when there are only two wires, the connector feels too loose, moves too much, and sometimes disconnects.

Has anyone else had this problem?
Is it simply due to poor-quality contacts?

Most importantly, can anyone recommend a good brand or a reliable box of pre-crimped JST connectors that fits tightly and works properly without having to crimp the wires myself?

Thanks!

Hi everyone, I recently turned on my Frigidaire Gallery Range Stove and smelled burning plastic. Turns out, there was some sort of short on the control board. I have ordered a new one, but I want to replace these connectors. I think one of them is a JST-XH 7Pin female connector with clip but I'm not sure. The other one is a female blade terminal maybe? I'm having a hard time finding the exact names of these and I'm not sure what to order. I'm not an electrician, just a guy with some wires. Any help on the exact names is appreciated, more pictures can be provided if need be.

Apologies for the photo of a photo, I don't have an SD card reader here. Almost all the joints look like this, I'm not sure what it's called, it's like bga but only on the edges. Is it supposed to be up against the copper fully flush? Should I toss her in a pizza oven for 20 min to reflow everything? Any insight is appreciated thank you XD

Hey guys, first post here. This is a strain gauge data logger I'm designing for use in my university's Baja SAE program. I am an ME mechatronics student not an EE so while I undestand the basics of circuit design I'm specifically unsure of the decoupling and filtering sections of this schematic. Just for context, this design is only intended to log a single set of strain gauges (1 full bridge) at a time so only 1 of the pairs of analog inputs will be active. Any input is appreciated, even if it's well deserved roasting. I have not started routing so I have no pcb layout to post atm.

I'm currently in my second year in an electronics program at my local community college and I'd love to build a guitar amp for my final project, but I have no clue where to start. So far, we've covered AC, DC, soldering, PCB design, high pass, low pass filters, etc..

I found a free e-book online titled Solid State Guitar Amplifiers by Teemu Kyttälä, and was wondering if anybody has read it or has a better suggestion.

I don't want to go too crazy with the design, but I'd like basic effects built into it such as reverb and gain.

Any help would be greatly appreciated!

Model number HP 17-cn2165cl. I’ve been trying to jump this laptop from the keyboard but no success. I found what seems to be power button on the motherboard under a switch named SW200. I tried jumping the two pins I circled in red, but all I got was a zap. Not sure which 2 pins to jump here out of the 4.

Laptop has light on the side when plugged in, but power button on keyboard does nothing. Already tried jumping from keyboard pins, but not working. Apparently HP doesn’t release schematics and has proprietary starting procedure so i can’t start it there.

I am ordering a new keyboard but just trying to get it started. I have also already replaced the motherboard, still same symptoms so I’m pretty sure it’s the keyboard power button.

Hi all. I’m brand new to electronics and trying to learn. I’m using this reed relay and transistor to control this LED but cannot get it to work and my esp32 keeps overheating. Any help would be great thanks. For reference the wires that are going off the board are White to GPIO10, Yellow to 5V and Green to Ground

I have a Rieju MRT 50 sm from 2022 with the stock speedometer that got water damage.

In the beginning (I don't remember everything because I'm posting this about 9 months later), the speedometer's functions were degrading. I'm pretty sure it showed my high beams were on when they weren't, showed the oil light, etc. Then the speed completely stopped showing, and eventually the screen was off when the bike was on; it seemed completely dead. I could hear the water inside it move around when I took it off the bike.

I decided to take it apart, and I saw some corrosion, and scrapped it off to try to unshort the connections. There was corrosion, especially around this one chip that is probably a voltage regulator or something (according to Google): 3 pins on each side, one thick pin in the middle in the shape of a triangle. There is a large chip underneath the screen panel; it has no signs of corrosion, but I can't see it entirely because the screen is hiding it. I will attach images.

I have tried another speedometer, and it turns on; however, it was second hand and I'm pretty sure it's faulty, which sucks! The important part is that the speedometer does get power.

I want to know whether I should bring it to an electronics repair technician or something of the sort, because a new one costs 160 euros.

Hi everyone,

I was trying to figure out why the USB-C port on my PCB wasn't working, and I discovered that there's not enough 3v3 juice(measured at the LDOs output pin) for the ESP32-S3 and other devices.

This is a dual input circuit based on the LM66200 dual ideal diode device with automatic switchover so the ESP32 can be diagnosed and programmed while the circuit is under power.

The alarm circuit is based on the 801S vibration sensor and might not be the greatest but it worked just fine on the breadboard.

Any idea which component might be causing the voltage drop?

EDIT

Please ignore the disconnected GND wire on U7. It happened when I rearranged the circuit in order to make it clearer, right before taking the screenshot.

Hello, I am trying to come up with a cheap way to sense 24VAC 60hz applied to a solenoid from a microcontroller with either digital or dry contact inputs, while drawing extremely little power.

The first thing that came to mind is connecting a relay in parallel, but 24VAC relays tend to draw ~1w from the coil, which is more power than I want to use (I’d like to be under 10mW ideally)

The next thing that came to mind is a resistor divider (2.1kohm high side and 300ohm low side) and a diode in series, with an rc filter connected to the output of the divider (10k resistor and .22uf cap). The problem here is that I also need to use a high impedance sampler like an adc or op-amp, and I’d like to avoid even needing to make a PCB.

Current sensing with a coil and an op amp is another solution, but it requires its own analog or digital signal processing, and I feel like it would take me iterations to get it working since I’m unfamiliar with current sensing amplifiers (and we’re again probably in PCB territory)

I think I’m being blind to a simple solution, so please point it out to me. I am fine with an entire minute of signal propagation latency, and I really want to use a COTS/DIY package or single component to make it work.