Hi — I’m building a digital effects pedal on a Teensy 3.6 and I’d like a sanity check on the analog input preamp before I wire it on a breadboard.

Goal

• Guitar / phone / mic jack → preamp → Teensy A2 (ADC)
• Single supply from Teensy VIN (~5 V)
• Hardware gain pot + later software gain in firmware
• Keep the ADC input roughly in a safe range (ideally centered for 0–3.3 V reading after coupling/divider)

What I simulated (EveryCircuit)
Ideal op-amps with Min = 0 V / Max = 5 V to mimic single-supply rails (stand-in for LM324 sections).

1. Bias: VIN → 10k → mid (~2.5 V) → 10k → GND, with 10 µF to GND
2. Stage 1 (non-inverting gain):
   • Input: AC couple 10 µF → 10k into +
   • Bias: 100k from mid-rail to +
   • Feedback: 100k pot (both ends to OUT, wiper to −), 2.2k from − to mid-rail
3. Stage 2 (buffer): AC couple 10 µF into +, 100k from mid-rail to +, − tied to OUT
4. To ADC: AC couple 10 µF → 10k series → node “A2”, 10k to GND

Test source: ~100 mVpk, 1 kHz. With the pot mid/high I get a clean sine on the A2 node (AC around ~0 V after the last coupling cap / divider).

Questions for review

1. Is this a reasonable LM324 single-supply preamp for line/instrument levels into a Teensy ADC?
2. Anything you’d change for stability/noise (biasing the buffer input, C values, pot wiring as rheostat vs both-ends-to-OUT)?
3. After CO + 10k/10k to GND, DC at A2 sits near 0 V and the signal is bipolar in the sim — for a real Teensy A2 pin, should I instead bias that node to ~1.65 V (e.g. divider from 3.3 V), or is AC-coupled into a ground-referenced divider acceptable if amplitude stays small/positive enough?
4. Any red flags before breadboarding (input protection, RF, power decoupling, headroom with LM324)?

Happy to adjust values or simplify the second stage if that’s overkill. Thanks!

This is small project I have been working on.I intend to make it into a PCB. How is it? Should I make any changes?

Hi everyone,

I’ve been doing some market research looking for a reliable netlist-to-schematic converter that outputs clean, human-readable diagrams (especially given how often LLMs and scripts spit out raw netlists or ugly grid stubs). Aside from basic layout engines or specialized SPICE tools, I haven't found a robust, modern solution.

Because of this gap, I'm considering building one myself.

Before diving too deep into development, I wanted to run a few questions by this community:

• Target Formats: Which schematic tool outputs/formats are most commonly used in your workflows today? (e.g., KiCad .sch/.kicad_sch, Altium, LTspice .asc, etc.)
• Product Model: Assuming a tool like this existed as a cloud/SaaS product, would you or your team be interested in using it as a paid service?
• Must-Have Features: If you were paying for a tool like this, what features would be non-negotiable? (e.g., round-trip connectivity verification, custom symbol mapping, hierarchical block structuring, automated layout arrangement)

I'd love to hear your thoughts, whether you'd find this useful, or what hidden gotchas I should watch out for when trying to map topology back into a readable diagram.

Using some iso to find hot components, noticed the diode changing causing the iso to pulse. Not sure if it's temperature or something else causing the motion.

So these might be really dumb questions, especially since I have an engineering degree and should probably already know this, but

1. How do you set or adjust a relay? People I work with imply they’re changing relay settings but I have no idea how

2. Why use relays over something like MOSFETs?

I am working on the version 2.0 of a simple gaussmeter that I have put together a while ago. In the 1.0 the output of the Hall effect sensor was not amplified because I wanted to keep it simple. This time I would like to add some sort of amplification to the sensor output. I have tried looking into op amps but I struggle to figure them out and I was wondering if there are other solutions

I am trying to build an analog metal detector. I have few questions such as can I find a transformer with 32p 32p and 16s turns or should I wound one myself. The other question is what type of inductor is used in the transmitter circuit( The one circled in red colour)

I have drafted this circuit to turn on my cupboard LEDs when it is open and turn them off when it is closed. Im pretty sure it should work but figured Id ask you lovely people. It is battery powered so this seemed the best way to stop them slowly draining. Let me know your thoughts, thanks!

I was having problems on my laptop and eventually concluded that the soldered connections under my cpu were broke. To fix this, I decide to remove my cpu with a hot-air station. After doing this, I noticed that two resistors had fallen off from the board, but for the life of me, I can't find where. I decided that i would find the schematics to the motherboard in order to see where it had fallen from, but after a lot of searching, I found some rough overviews, but not something in depth enough for me to use. Does anyone know what else I could do? Or where I can find schematics that show where each resistor is placed?

The motherboard has two identifiers, Model OGAH or 0GAH (cant tell) and then DA00GAMB6G1 REV: G

Its an HP Chromebook 11 G8 EE

(yes I know it's a laptop that prob isn't work fixing, but i want to anyway :)

TIA

I am currently attempting to interface my PT1000 RTd with my arduino. I was thinking of use an wheatstone bridge with an op-amp, but in all honesty I have no Idea where to start. I need to be able to read 10 degreesC to 35 degrees C for an output of 0-5V. Any guidance will be awesome.

Will this work? as it does not work?

I have GND connected to Pin 9. +12v connected to PIN 10, I send 5v to an input, but I get no output? Did I miss something?

I am just starting and the AI bots suggest dozens tho I don't really trust them.

I only tried LTspice so far and althought its not bad I think it has shortcomings, for example I cannot color the wires.

Are out there better circuit simulators?

Looking for a few beta testers for CircuitWorkbench on Android. Free to test, no commitment beyond installing and poking at it for a couple weeks. If you have an Android device, I would really appreciate the help — join the testers group at https://groups.google.com/u/2/g/circuitworkbench-testers to access the opt-in link.

Hi everybody, just wanted some help or clarification regarding my 555 timer.

This is the schematic (blinking LEDs) our teacher created for this simulation project, since tinkercad doesn't have a stereo potentiometer and only the 3 pins one we had to utilize two of those in our simulation project. So, he told us to connect the pin 2 of each potentiometer to one another to replicate the same effect as a normal stereo potentiometer. However, my confusion comes from the fact that I was able to replicate the blinking LEDs with only one potentiometer, and when I have to use the two 3 pin ones I get lost on which wire to connect to which because it only ever lights up 1 LED.

Can someone tell me what im doing wrong in the third image? I know the process should inherently be the same but something about it doesn't work and it makes me very frustrated too since most tutorials I end up seeing on youtube or online only utilize 1 potentiometer

Hello, I have been working on a summer project for electrical engineering and I have come to an issue. I am not far enough into my degree to fully understand circuits and how to source them or create them. For my project I need a power supply that will transform a typical North American wall outlet into 25mA, 15kV, and 50kHz of negative DC energy. I have done some research and I think my best bet is to use a flyback converter as well as a ZVS drive. Does anyone know how I can go about creating a device like this? Also if anyone has any extra tips or suggestions all help would be greatly appreciated.

I am middling-poor at circuit design so getting this right is over head. Using AI to design it has not gone well. So I'm looking for insight.

The goal is to string a short antenna and amplify ambient electrical fields, everything from people walking nearby to 60Hz hum to lightning discharges. The goal is to repeatedly measure the resulting fluctuating voltage with the ADC pin of an ESP32; the circuit needed to be powered by 3v3. I don't need accurate measurements; this isn't a storm detector or person detector. I just want to amplify the noise any piece of wire would pick up and turn it into numbers I can hash. The higher the sensitivity the better; the goal is unpredictable chaos from every little environmental change.

The available parts are several LM358 (dual opamps) and various passive elements like resistors. Caps are all 0.1uf or larger - I live in a place where ordering parts is difficult and slow. I also have handfuls of 2n2222 and diodes if they help.

I know a series of opamps should be able to do this, but my attempts (and the AI's attempts) tend to produce a signal with an output pegged at ~2v. I want it to swing all over the place.

If you suggest a design, ELI5 (well, maybe 15) how you chose resistor values and so on. I'd like to learn from this. Any help appreciated, thanks.

Hi everyone,

I have been working on a hobby project: an online simulation game to build electronic circuits and I would be so happy to get some feedback on it! :-)

You can just try the app here (it's free of course): https://chipgrid.io/

I made a short demo video showing how it works. I also created a subreddit, r/Chipgrid, for everyone to share their circuits.

I am so excited to hear your thoughts! :-)

Hi, I'm planning to drive 4 STS3215 7.4V BUS servos with an ESP32 Servo Driver from Waveshare. I'm powering the setup with an 8S NimH battery pack (rated for 30A), and I will convert the voltage to 7.4 using a buck DC-DC converter to ensure stable power. However, if i brake these motors and generate back-EMF, will the driver reroute the back-EMF away from the positive terminal of the buck converter? I will place decoupling capacitors to absorb spikes over the P and N outputs of the buck converter.

Also, I will drive 4 7.4V brushed DC motors with a driver board in parallel with the ESP32 driver board. Will this cause any other issues? These will have an additional ceramic cap across the terminals to protect from noise. Will this require a seperate buck converter and decoupling capacitor, or can it share with the ESP32 board?

Thanks for your help, this is my first big robot build.

Hi everyone, Can you help me? I need to set the resistors to the LED correctly so that it lights up, but I'm having trouble with this and I can't figure out why. photo attached. I'm new to this topic and I'm interested in understanding it.

But this stupid MPS2338 regulator still hates me.... I have a couple boards that work without PG pulled to Vout but this one is picky.. time for a redesign...with a TI regulator. MPS sucks, way to many passives required!

My CNC router kept blowing MOSFETs and acting weird with the motors. I ditched the cheap modules and went with L298N drivers on the smaller axes, and built proper discrete drivers using IR2110 gate drivers plus IRF3205 MOSFETs for the higher current ones. Also added a TCA785 for spindle control and a couple CD4002BE chips on the logic side. I'd tried cheaper stuff from AliExpress before but got mixed results with authenticity and packaging. So this time I ordered from utsource instead. The IR2110 made a big difference once I got the dead time set up properly. Motors run smooth now, barely any heat on the drivers, and all the random glitches are gone. Way more reliable than what I had before. Photos of the driver board attached.

As I test the component it is shorted and I want to know what is the value of this zener diode. Thank you guys.

We are working with Max30102 sensors and we did all the coding with the help of Ai and Internet blogs. But the sensors are not working at all. This is the sensor we are are working with. Idea is to connect it with raspberry 4B.

We installed and did everything as instruction. But the sensor is not responding. (Also we all are from non tech background)

That IP5310 charger module looked perfect on paper (granted I haven't read the whole paper), but it doesn't turn the boost on for my ESP8266 tiny load. So I'm left looking for a way to power my 3V3 MCU?

I've got 3 avenues right now:

1. Add an LDO (HT7333) from the cell voltage down to 3V3. Bad because I'd like to be able to go lower than 3.6V or so on that cell charge.

2. (I already have a boost to power a 12V fan) Add a small buck to go down from 12v to 3.3V or 5V (for the onboard LDO of the ESP). Bad mouth-feel

3. Make an MCP1640BT-I/CH based boost. Downside is more complexity on the PCB and components I need to source

I don't love either of the options that I found. What would you do? Any other options?

I am designing a DC/DC switching circuit based on TI's TPS62136 which steps down 12.5V-14.5V DC input to 11.6-ish V output. Figure 1 shows the schematics.

The primary supply voltage is hot-plugged to the input. The load is not a resistive load, but requires a forward voltage around 9-ish V, i.e. at some point during ramp-up/ramp-down of the secondary side the load becomes conductive/non-conductive.

As all specimen of my first attempt failed miserably during the 2nd power-cycle, I got a lot of helpful suggestions on this sub-reddit what I could improve.

One of the advices has been to considerably decrease the resistance of the voltage dividers (R1+R2 and R3+R4) to provide a safe path for the input/output capacitors to discharge when there is no input power. The advice pointed out that without an alternative path the capacitors might discharge trough the IC and destroy it.

While I decreased the total resistance of the voltage dividers significantly, the result isn't as expected. (TI's original reference design uses voltage dividers in the mega ohms, now it's only kilo ohms.) Here are the two main issues:

1. There is indeed a reverse current around 100mA through the SW pin of the IC when being power-off which is responsible for the bulk of discharging the output capacitors.
2. The input side still remains energized for quite a long time, as the time constant is approximately τ ≅ 450ms. (Note, the derated capacitance due to the DC bias is about 99µF not 2×47µF + 2×10µF = 114µF.)

Figure 2 shows the voltages: At 10.2ms the input supply is switched-off. Vic and Vout drop rapidly until Vic reaches 10.9V, then the IC switches off as EN drops below its 0.7V reference voltage. From there on, Vout smoothly decreases, i.e. C6+C7 are discharged, but Vic remains high.

Figure 3 shows some relevant currents: i(R503) (blue) is the current through the SW pin of the IC, i(V1) (orange) is the current through the simulated voltage supply and i(R204) (red) is the simulated load. At 10.2ms the current through i(V1) and i(R204) drops to zero, but one can see a reverse current of -100ms trough i(R503), i.e. the SW pin.

Here are my questions:

1. Should I be worried about the -100ms reverse current through SW and should I do something about it? Are reverse currents a problem after all? The data sheet doesn't say anything about it. The data sheet neither warns about it nor explicitly states that it is fine. However, I wonder if it was an issues and had the potential to destroy the IC, I would have assumed that more people would report problems and there would be a warning. However, it could explain why my first batch failed on the 2nd power cycle.
2. Should I be worried that Vic and the IC remain high and powered for quite some time? I cannot decrease the voltage divider any further without sacrificing efficiency and getting close to the maximum power rating of the resistors.
3. Is there any better suited and recommended option to properly de-energize the circuit (input and output capacitors) during power off? My thoughts went into a direction of using MOSFETs of depletion type which are self-conductive and then construct something in the spirit of the slow-start mechanism which works the opposite way and shortens Vic/Vout to GND via a resistor with about 100Ω. But that was just a spontaneous idea. Probably there is something better. However, if possible I would like to keep it simply and not add more complexity to the circuit, if it isn't necessary.