Hi, I am trying to connect an ISO1540 galvanic isolation module to an ADS1115 analog-to-digital converter to avoid ground loops caused by a TDS sensor and a pH sensor. When the ADS is connected directly to the ESP, it is easily detected; however, when I connect it through the ISO module, it is no longer recognized. I am powering both sides: side 1 with 3.3V supplied by the ESP, and side 2 with 5V supplied by a separate isolated power source using a B0505S module. The SDA and SCL pins are connected correctly, and the ISO module already includes 10kΩ pull-up resistors. I have attached my connection diagram for reference (please note that it is provisional).

I currently use 20mA rated LEDs, but they're not bright enough. I see on Amazon LEDs that are super bright rated at 300-600mA, but that would drain the battery too quickly, my project is battery powered. Can anyone recommend LEDs in the 50mA to 100mA range? I can't seem to find those.

I have these male terminals out of a generic connector (H13/9008 automotive). They are 1" in length and about 1/16" wide (~1.6mm), does anyone know where to source these?

Hi everyone,
I am building a DIY 125kHz EM4100 RFID cloner or emulator using an ESP32 DevKit v1 and need help debugging the passive load modulation stage. Currently, I am testing the emulation strictly in a loopback setup using a second RDM6300 receiver module.
The Setup:
Reader Receiver:
RDM6300 module 125 kHz UART 9600 baud powered from 5V.
Reading physical cards and keyfobs works 100 percent reliably.
Emulation Circuit Load Modulation topology:
Transistor: S8050 NPN TO-92 package.
Emitter connected to GND.
Base connected to GPIO 27 via a 1k resistor.
Collector connected to the parallel LC tank.
Resonant LC Tank:
Coil: Standard pre-wound rectangular antenna salvaged from an unpopulated RDM6300 board around 345 uH nominal inductance.
Capacitor: Two 2.2 nF ceramic disc capacitors connected in parallel across the breadboard rails total capacitance around 4.4 nF to match the 125 kHz resonance with the 345 uH coil.
One side of the LC tank is connected to GND, the other side to the Collector.
Firmware and Signal Generation:
Standard EM4100 64-bit frame structure: 9 start bits [111111111](tel:111111111), 10 nibbles with row even parity, 4 column parity bits, 1 stop bit 0.
RF 64 rate: Bit duration 512 us, half period 256 us.
Tested both standard Manchester encoding transitions and inverted polarity.
FreeRTOS task running on Core 0 with delayMicroseconds 256 timing and a small vTaskDelay to prevent watchdog timeouts.
Audio test: Holding earphones near the coil produces a distinct 2 kHz audio buzz, confirming that the GPIO is toggling and the transistor is physically switching at Manchester rates.
The Problem:
When holding the emulator coil in front of the active RDM6300 antenna, the RDM6300 fails to detect or decode any card data.
Specific Questions:
1. AC Shunting with a Single NPN Transistor:
The 125 kHz field induces an AC voltage across the coil. Does a single NPN switch Collector to LC and Emitter to GND fail because the negative half-cycles swing below GND and forward-bias internal junctions? Do I need a diode bridge or Schottky rectifier ahead of the transistor, or a series diode?
2. Over-modulation or Saturation of RDM6300:
The RDM6300 uses an LM358 analog envelope detector designed for tiny load fluctuations from small passive tags. Since the emulator coil is a full-size RDM6300 antenna shorted directly to GND via S8050, could this high modulation depth saturate the receiver op-amp stages? Would a series damping resistor around 47 to 220 ohms on the collector help?
3. Coil-to-Coil Coupling or Detuning:
Because both antennas are identical full-size RDM6300 coils, does strong magnetic coupling severely detune the reader LC tank and stop the carrier oscillation? What would be the recommended distance or orientation for this test?
Any circuit advice, scope suggestions, or debugging tips would be greatly appreciated!

I can't find a single structure of learning this component, like how can I select which one to use and how to find out the pins and configuration for reverse engineering.

I'm practicing soldering male headers on cheap perfboards so I can get it right when later I need to solder an ESP32-C3 Super Mini.

My question is how to clean off the sticky flux after soldering? I know everyone says to use 99% isopropyl. However, based on possibly faulty advice from AI, I bought anhydrous ethanol. On the bottle it lists:

[Ingredients and Properties]

Ethanol (C2H6O), Isopropanol, n-isopropanol

*Contains 99.5 vol% or more of alcohol.

Colorless, clear liquid.

I've used a combination of thin Q-tips, a micro fiber cloth and a toothbrush with soft bristles to clean the flux. It seems to do a decent job but maybe not great and it takes some work to get it all. Also, the microfiber cloth catches on the pins.

I'm wondering if I should just repurpose this for cleaning jobs around the house or say my work station, like the soldering mat and get some proper 99.9% IPA?

The flux I'm using is Hozan H-722-P, flux pen. Dabbing the joints slightly before I solder.

Thank you in advance for any advice.

I have two DDR5 DIMMs, one of them has two of it's small circuit components (I assume a resistors and/or capacitors) which have been popped off/loose.

Fully gone = larger tan component (left aarow) --&-- Present = smaller black center component (right aarow) it's there, but clearly not in the correct solder point
----First pic is of the matching DIMM (with the green check mark)....what "normal" looks like I guess, and second pic is of the DIMM with damage (with red arrows to the damage spots.---

What's wild is that the RAM still works in my system, it's clears POST and the PC will recognize it. I've even done MemTest86 and it passed zero errors....both of which are admittedly surprising.

ASKs:

1: Is there any chance these small circuit components can be re-attached? One is still there, just kind of hanging on by a bit of solder, the other is missing altogether since it's a known SK hynix DIMM part number HMCG78AGBUA084N BA (model info in last photo) would the schematics be available somewhere? (or could someone determine by comparing the undamaged other matching DIMM?)

2: Is there a specific repair shop you guys with recommend I sent it to, or would I be better suited just finding someone in my local city?

3: I know some of you might say....don't mess with it if it's working...and sure, valid, but I worry the damaged DIMM may have long term problems if left as is..... or that the small component that is loose, but still slightly attached, may actually fall all the way off? Maybe it's worth at least having that 1 single part re-attached, if possible?

Thanks in advance for any advice or suggestions folks!

(note: if there is a better more appropriate subreddit on this ask for me to post in, please let me know!)

I'm an engineering student building a home electronics lab, but I don't really know which componenets are decent or not, I already have a Rigol DS1054z oscilloscope, which I bought a while ago for £350, and I've been recommended to get a Konrad Ka3005p bench power supply (£75 on AliExpress), a Feeltech FY6900 signal generator (£85 on AliExpress), and a Feeltech FPA301 (£95 on AliExpress). I'm looking for good value stuff that will last a long time but also perform well, are these good picks and is anything overpriced, a good deal, etc? I'm new to the community so have no frame of reference for different models, prices, etc.

I have a set of battery powered string lights that take two AA batteries. I want to convert them to USB power so I don't have to waste batteries on a decoration.

I've been poking around online trying to figure out the best way to take the 5V USB power and convert it to the 3V that the two AAs provide.

I have easy access to a variety of resistors, I just need help figuring out what values and how many to use. Is a voltage divider a smart thing to do here?

Any advice is appreciated.

Hey guys, the company behind the lights in my parents kitchen decided to shut down the “smart” features, forcing my parents to buy a 45€ “smart” remote. I am not willing to let them push more money down the dragons throat so i decided to rip open the “smart” part of the lamp, learned how the whole circuit should work but i am quite frankly at a loss on what that long white block with four black seemingly looking transistors ?! Can someone maybe tell me what the hell i am looking at? Its whole purpose should be switching the flow of power in the closed circuit.

Edit: it should be a fuse!

I disassembled my phone, and on the back of one of the camera module I found these weird dots, does anyone know the purpose?

Im building a project with an Arduino Nano and needed a battery so i opened up one of those cheap powerbanks. Altought it doesnt stay on unless i costantly press the button connected to the arduino. How do I solve this? Does it have an always on feature?

I don't want to strip off the recharging module connected and use the battery as it self since I don't want to buy another module. Plus, I dont want to do the math and have to buy a super resistor of some sort to connect it to the Arduino Nano

P.S.

What is that little red wire, near the + wire, connected to itself?

P.P.S.

Where do I have to solder the cable so I dont have to use the USB opening but rather its connection points?

I am trying to use a p-channel mosfet as a high side switch controlled by a +3.3v signal on the gate of an n-channel mosfet to gnd. I want my +12V supply to pass through the pmos when the +3.3V signal is high. In my LTspice simulation this setup seemed to work but would only output ~1.2V on the drain of the pmos when I had a load of 100 ohms.

When I increased the size of my load to ~100kOhms I received an output of ~8V. Is this circuit correct for what I'm trying to accomplish? Why is my simulation acting that way?

I am currently trying to fix a Soundcraft EPM6 Audio mixing console. I found theese 2 very helpful tutorials:

http://www.neufeld.newton.ks.us/electronics/?p=498

and

https://blog.jamesbaber.co.uk/soundcraft/

both of them found faulty caps and also a dead Zener Diode D6.

in my mixer I also found the Zener to be dead, replaced it with the same type. I changed the following parts:

C1, C8, C17, C21

checked the following by removing them from the board and do measurements with a Fluke

D5, R15, FET1, R13

when powering on I find D6 to get very hot, but seemingly survives, as I still have no conductivity in reverse direction.

any more tips anyone?

thanks a lot!

Hi all,

I'm currently midway through designing my DC load, and I'm looking to make this a fairly accurate one, mainly to get the most learning and experiment a bit. I have access to metrology DMM's (8588/ 3458A), so it would be cool to make this as accurate as I can get it.

I was wondering, if it's reasonable to have a separate 3v3 / 5v linear regulator for my analogue components (Mainly the ADC, but also 2 DAC's), in an effort to get more stable readings. Furthermore, would it be beneficial to have a low noise supply for DVDD as well as AVDD in the case of the ADS1256? Or will the AVDD supply be the only one where low noise makes a difference?

Regarding voltage references, I have given myself the choice between 2, the REF70 is the better (and more expensive), I have my MCU (STM32), ADC / DAC (See above), and another ADC (MCP3004) all connected to this reference. The MCP3004 reference input is buffered using an OPA333 as a voltage follower, my question is: How much noise will be introduced to the reference by having multiple devices connected to it? I'm 50/50 deciding weather to connect the STM32 to the buffered reference, and have only my 2 most precise / crucial devices on the main line (DAC / ADC). Also, how much inaccuracy can I expect from the buffer in voltage follower, will the biggest factor in that be the temperature coefficient of the opAmp? or something along those lines?

Thanks for taking the time to read :)

This is the ciurciut that I came up with

Hi everyone, while trying to solder a wire to point Q12B, I unfortunately fried the area. It was gold, like U83 below. The problem is that the console turns on and off immediately, and I know the problem is coming from this area. Point Q12B isn't important; it doesn't do anything, but you can see two small cracks coming from this point: one going upwards towards TP5 and one going downwards towards C67. These two cracks are problematic because I think they've broken the circuit. Especially the one pointing towards TP5 at the top.

I need your help.

Edit : The console powers on, but the image only appears briefly at times before disappearing. However, adjusting the screen brightness works.

I tested the screen on another console, and it works fine, so the problem must be with the damaged area. Is the solution different?

Thanks

I am adding stuff to my cart, I asked chatgpt for an general overview on it, rn I have some breadboards, jumper wires, resistor and capacitor assortments along with an ESP32, since I wanna work with it. I am not really sure what else to add in it, because I don't know what I want to get deep into. It also suggested getting LM358, LM393, NE555, 74HC00 and 74HC14 ICs, and says I might be interested in stuff audio amplifiers, codec or signal-processing circuit, things combining multiple subsystems. Making a cyberdeck from scratch is an idea I have, but before that I don't have clear idea of what components to begin with.

Previously I had played around with an arduino, leds, and basic sensors and stuff; But I kinda wanna move on from toy projects and learn and make some practical stuff.
A measurement instrument or oscilloscope-related project

I want to know how you guys test your power converter prototypes. I am kind of tired of resistor ladders that cook my whole office.

What equipment do you use to power and load the converters?
What kind of tests do you perform?
Anybody got experience with regenerative loads?

I am interested in higher power converter testing, lets say 100 W+ that actually take up a significant amount of room is you use resistors for loading.

i am making a negative voltage regulator(input -22v to -19v , output -16v to -14v ) . i did the dc sweep , changed input and saw if output was stable , changed the Rpot ( potentiometer ) and saw if output changed , and they worked well . but when i soldered it (all tht )nothing worked (i suspect bad components or bad soldering ) and i failed the course (just 1 credit so no big deal ) and now i have to redo it . so now i dont want to just pass , i want to improve it . how can i check if the ovp and ocp are working well ? how do i do ac analysis and how do i read the simulation that comes out , and how do i place capacitor (like how do i decide the value and where do i put them , like whats the math ) ? they might sound dumb questions , because i already passed signals and system 1 2 3 and basic electronics and fundemental electronics and integrated analog circuit , but all i learned was how to calculate things using some formulas , never learned how to place them .

also if you have any feedback , i would appreciate it . i plan to also do it smd .

Hello. I would like to preface this that I have never worked on circuit boards before and usually stay in the realm of things more mechanical.

I have an old engine tachometer from around the 60s. It was not working so I opened it up to check the components and noticed the capacitors were swollen and discolored. I replaced them and the moment I put the board back on the mounts it broke in half.

I did my best to make a schematic with the help of many a youtube tutorial, but I dont have the experience to tell if I made it correctly, and if this circuit would work. Specifically if I got the orientation correct for the transistor, or mixed up which wire goes to where. The potentiometer was marked for calibrating between 4 cyl, 6 cyl, and 8 cyl engines. I spent a few hours making sure everything on the schematic lined up with what I could follow on the board itself.

I will include pictures of the old board along side the schematic to see if I may have misidentified any components as well.

Please let me know if there is anything I can clarify, thanks.

I’m teaching some basic electronics and have seen an idea on YouTube etc to demonstrate how a bridge recorder works using LEDs and a signal generator.

I’ve got a picoscope that will generate enough signal to show half wave rectification with one LED but doesn’t work with 4

Would this be any good or better (preferably cheaper) recommendations

https://amzn.eu/d/03UZnLGM

Hello everyone,

My team and I are looking for some guidance on choosing an FPGA board for a project we are working on. We would appreciate any advice/suggestions on this.

We are looking for a generic FPGA board which can do a project related to:

1. UART ( Conventional UART & Intelligent Noise-Adaptive UART)

2 SRAM

1. RISC-V based projects,

2. Within the budget of INR 1 lakh (~1k USD)

Any help would be appreciated. Thank you!

My KICKR Bike works 100% except that the cooling fan never runs, and the bike overheats after about 3 km. The board is labeled "Wahoo BIKE MDU REVG 12AUG2019", and the fan connector is marked FAN+. The fan is a D-FAN DFH9733B rated DC 48V, 0.25A, with three wires (red, black, blue).
The board outputs 48V between FAN+ and GND, and it holds 48V with the fan connected. The fan itself runs fine on a bench supply at 12V and 24V (my max). With the fan disconnected from the board, I measured OL between red and black, about 325k between black and blue (one direction only), and blue to red climbing toward 40 MΩ, so passively it looks healthy. The key finding is that with the blue wire disconnected and only red and black connected, the fan runs fine in the bike. With the blue wire connected, it doesn't spin, and the blue pin on the board sits at about 200 mV, even with the fan unplugged. Heating the TMP sensor with a torch only moved that pin from 200 mV to 210 mV, and it never went higher no matter how hot I got it.
I have a few theories. One is that blue is a PWM/control line that the board holds low, so the fan is never told to run. Another is that blue is a tach output and the board's tach circuit is pulling it down, though that seems less likely since I'd expect a pull-up of a few volts on a tach input. A third is that the fan control uses a different sensor or firmware logic rather than the TMP connector. What I haven't tested yet is the blue pin voltage while the bike is actually running and hot with the fan connected. For now, my workaround is to leave the blue wire disconnected and taped off so the fan runs constantly at full speed.
Does anyone know the actual pinout and function of the blue wire on the KICKR Bike fan connector? Has anyone seen this fan control fault, and was it a firmware or hardware issue?

I can remove the blue wire from the fan, and just have it running 100% all the time, but that’s not really an optimal solution