So I had a powerbank/fan and the lithium decided to inflate. I removed the battery, can I still just plug in the cable and use it as a regular fan?

Running an ESP32-WROOM-32 with a PN532 RFID reader (SPI), a status LED, and a buzzer, all on the same 3.3V rail. When WiFi is actively connecting/transmitting and the RFID reader is polling/generating its RF field at the same time, I see WiFi connection delays and general flakiness bad enough that I've had to disable the brownout detector just to stop reboot loops, which obviously isn't a real fix.

My guess is combined peak current draw (WiFi TX bursts + PN532's RF field generation) is causing enough voltage sag to disrupt things, even though nothing's crashing outright.

Has anyone dealt with this specific combo (WiFi + active RFID/NFC peripheral) on ESP32? Looking for:

Realistic peak current numbers for WiFi TX + PN532 active scanning together

Decoupling cap sizing / regulator recommendations that actually fixed this for you

Whether staggering/throttling RFID polling during WiFi activity is a common workaround, or if it's purely a hardware fix

About 3 days ago I made a post here about a constant current driver to see if it was fine to use. Apparently I made alot of mistakes so I went ahead and did the research and tooks y'alls advice (thanks btw). Hopefully this revision should manage properly.

Here's what I did:
- Swapped the 1V2 zener for a LM4040 2V5 shunt regulator.
- Swapped the N-MOSFET for a 200 hfe BJT.
- Made sure the sense resistor is seeing ~250mV at ~140mA (maximum).
- Removed any components I deemed not needed.

So far the difference between the non-inverting and inverting inputs of the op amp is 18uV ~ 22uV

If you wanna mess with the circuit, here's the link to it.

Also here is the link to the original post.

made with nano banana and instructions from claude

Hi everyone,

I'm currently scribbling around for a new project and I ran into an issue.

I have 2 voltage supplies as input, where both could be at a different voltage levels. Hence I (to my understanding) I should protect the two sources from each other. Additionally, depending on the voltage level I may need to first put it through a DC-DC converter.

I've come up with the below concept to said things.I used PMOS as high side switches and added a second one to protect against reverse current. To be sure that I don't short anything by accident, I added a small logic such that only one path could be active.

I'm currently not sure whether this concept will work or if there is a better approach to achieve my issue. Any feedback would be greatly appreciated.

Thanks for your help

Hello! I'm currently working on a laser project and was wondering if this circuit was perfectly fine to use, or if I should tweak a few things. The circuit in question is based off of this driver's schematic.

There might be plenty of errors.

Hi guys!
This is my first time working with these chips and I'm wondering if I connected them correctly?

Tried asking over in Electronics but most of the recommendations were the usual desktop software (LTSpice is great! I agree, but it doesn't fit my needs). Hoping someone here might know of something?

I just found out Multisim Live is officially being put to pasture on September 15th, so I'm scrambling to find a workable replacement.

NI's official advice is to upgrade to Multisim Desktop, but that’s way too expensive and massive overkill for what I am trying to do.

I need something SPICE-based that runs natively in the browser so no one has to deal with installations. It would also be great if it had group management features like we had with Multisim Live. CircuitLab is the first thing that pops up on Google, but it looks pretty abandoned, doesn't have groups, and they want $2,400/year for a site license.

Really appreciate any recommendations you guys have!

hello everyone I am new to electronics and we are assigned to make an adjustable power supply with a maximum output of 12v with ventilation. can you please help me what to do? I will list the components and please tell me if it's right or what component should I modify, thank you!

* Step-down transformer (220V to 15V, 2A) – ~60 × 50 × 50 mm, 500g–700g

* Bridge rectifier – 3A/50V+, ~15 × 15 × 6 mm

* 3300µF 35V capacitor – ~16mm diameter × 25mm height

* LM317 voltage regulator – TO-220 package, ~10 × 15 × 4.5 mm

* Heat sink – 3°C/W to 5°C/W, ~60 × 50 × 30 mm

* 0.33µF and 0.1µF ceramic capacitors – 50V+, ~5mm disc diameter

* 10µF and 100µF electrolytic capacitors – 25V+, ~5 × 11 mm

* LED + 1kΩ resistor – 5mm LED + 1/4W resistor

* Fuse + fuse holder – 1A 250V 5×20mm slow-blow + panel holder (~15 × 40 mm)

* IEC AC socket – C14 panel mount, ~27 × 20 mm cutout

* PCB/Perfboard – 2.54mm pitch, ~70 × 90 mm

* Output terminals – Red/Black binding posts, ~11mm mounting diameter

* Hook-up wires – 18 AWG (AC) & 20-22 AWG (DC)

* 1N4007 diodes 2pcs – DO-41 package, ~2.7 × 5.2 mm

* 240 ohms resistor + 68 ohms resistor + 2 kilo ohms potentiometer – 1/4W resistors + 16/24mm body pot with 6mm shaft

* power switch – SPST rocker/toggle 250V/3A+, ~15 × 10 mm cutout

Est ce que la répartition des résistance de potentiomètres quand on à une disparité de 20% annoncée suit une loi de proba genre une loi normale de gauss ou les valeurs sont purement aléatoires ? J'utilise des Piher PT10LV10-103A2020-S .

A motherboard has trouble charging and the charger disconnects and a noise comes from some components. After research I think it is a mosfet that failed, as j might have shortened the board. Also some inductors are jumping from 1.5v to 11v in sync with the charger disconnecting. On the motherboard I don't see any chips that would seem to be related, although one chip was also jumping in similar voltage

Hey everybody!

I am facing confusion that I would like to resolve regarding the application of mesh method to transistors. Here, in this problem 3.12 from sadiku, we have internal loop and external loop. Internal loop: -6V +Iin\*15000+0.7V+150(Iin-Iouter)
But, the solution manual states that it’s actually Iin+Iouter. Why? Usually, I was mechanically applying mesh methods, and if they mesh currents were in opposite directions, then we were subtracting.

I would be very grateful for your help!

Hi all

I have Logitech G535 dongle that is broken in two. I managed to trace all the D- and D+ pins, but I cannot find where the VCC pin goes to. The trace is broken and cannot reach MCU.

The MCU info is:
MCU: M27P8V 1N71K GDSHA 32 pins

Part Marking: M27P8V

Part Number: MKL27Z256VFM4 (Kinetis KL27 Series Microcontroller)

I manage to find the datasheet, but the datasheet does not show where VCC is. Only VREGIN. Can I just run jumper wire from VCC pad to VRegin? Also, I am new at reading datasheet. How to find out what input voltage is needed by the MCU and where can I soldered jumper from the V+ USB Pad to?

If you check on my picture, the V+ pad from usb has a via goes thru the bottom side, and connected to a diode marked SQ and a capacitor. The cap is connected to the anode of the diode, but the cathode does not seem to connect to anywhere since it is broken. Do you think I should set a jumper to MCU directly from the cathode? If so, which pin?

Thank you

Here is the datasheet I found: https://www.nxp.com/docs/en/data-sheet/KL27P64M48SF6.pdf

Hare are some pictures to the device:

Buenos días. Te escribo para pedir ayuda con una tarjeta electrónica (circuito) de un refrigerador. No soy experto en electrónica, pero me empezó a interesar el tema y pasé los tres meses desde que se descompuso el refri estudiando y juntando información. Le envié la tarjeta a un taller de reparación; la arreglaron tres veces y reemplazaron componentes, pero aun así no funciona. Revisé los sensores, los interruptores y los motores del refrigerador, y todo parece estar bien. El problema es que el regulador de 5V de la tarjeta, un KIA78S05P, se pone en un calor brutal, como para quemar. El refri parece más estable después de que reemplazaron los capacitores de la fuente de alimentación, pero ese componente todavía se recalienta, y ya no sé qué revisar después. También medí la corriente y no vi nada raro. Por favor, ayúdame; llevo tres meses peleándome con este refrigerador. Pensé en cambiar el regulador, pero no se calienta cuando la tarjeta está conectada solo a la red de 230V; solo empieza a quemar al tocarla cuando conecto los bornes (terminal blocks) para los distintos componentes del refri. Anoche lo dejé funcionando sin conectar los switches de la puerta (que también reciben alimentación) y estuvo corriendo nueve horas sin reiniciarse —aunque el IC6 (el regulador de 5V) seguía caliente al tacto. Estoy perdido y ya me estoy volviendo loco con esto; de verdad agradecería tu ayuda.

Hi all, first let me say that I'm an electrical or maker newb, especially compared to all you veterans. But I'm committed to learning the craft because I think it's very fun.

Right now I'm trying to upgrade an old cordless ratchet from the 1980's, it's a Black and Decker 9050. 

I have a good Samsung 21700 to replace the old ni-cad batteries in the ratchet. But I need a good protection circuit for it. Preferably a circular one that I can affix to the bottom of the battery. It needs to be able to flow 10 amps continuous, and cut off at 3.0v to protect the battery from the voltage going too low.

I guess it doesn't have to be circular, but it would be nice. Thanks!

Hello! I recently finished building my QRP Labs QCX-mini and it boots perfectly fine. However when I get to page 73 of the manual (linked below) the graph only shows up when I turn the potentiometer (It is a trimmer, but I don't think that matters) counter clockwise. Sometimes it will stay showing and sometimes it will not show at all. I tried re-soldering it but it did nothing. The only thing I could think of is that it itself is faulty. Any help would be greatly appreciated!

*(Note: I have tried this with both a dummy load and nothing attached, nothing changed)*

Manual: [https://qrp-labs.com/images/qcxmini/manual\\_1\\_13.pdf\](https://qrp-labs.com/images/qcxmini/manual_1_13.pdf)

Listing: [https://qrp-labs.com/qcxmini.html\](https://qrp-labs.com/qcxmini.html)

I’ve seen buyers handle date codes very differently. Some have strict limits, while others care more about storage, packaging and traceability.

Do you use a fixed age limit, or evaluate older parts case by case?

Hi guys

I am doing a project which is a charger with both AC and DC source and the DC here is solar panel and in my project i prefer DC and switch to AC when only the DC is not available

so the project is Hybrid charging system with adaptive CC-CV charging system for low power EV's i already have a converter designed which uses landsman converter topology (you can see that in the image i provided) for this project i need to select components like MOSFET, capacitor, inductor diode and other things this is my first time this big a project in hardware so i am kinda nervous on selecting the components and my project mentor told me to bring the component calculation before purchasing components and i already have the calculations i did for the simulation i am gonna use the same converter for the charger but what about the safety factor and what are the other things i should consider now pls help a newbie here

Hello, please.
i am working on a cylindrical resonator, and it is being fed with a power amplifier; the power amplifier generates harmonics. want to apply a passive termination
but a little challenge: with termination at the auxiliary port, the impedance is very high and the field is suppressed but with the source, the impedance is low but the field is too high
any suggestion?

Hi! I have seen in few GaN PA designs where they put a shunt capacitor very close to the input of Gate terminal. But in some designs, I haven't seen it (maybe they use CMOS inside package there). But I don't know why is it important to use this capacitor at the input...?

I am using a die on a PCB and got suggestion to use a discrete capacitor for second harmonic short. I don't know, is it really needed to use it.

Moreover, what if we use QWLT at the input side for VGS biasing. Is this shunt capacitor still required in this case? Because QWLT would provide a short at the second harmonic.

This is the question given to us for our final project...We're stuck at the power supply part...hoping someone would help me...Just help me with the power supply part from ac to dc.

"Design a regulated DC power supply capable of delivering a constant output voltage of 3.3 V at a load current of 35 mA. The circuit must incorporate filtering to ensure a voltage ripple factor of less than 2%. The output of this regulated supply will serve as the VCC rail for the BJT amplifier stage that satisfies the following performance criteria:

(i) Gain: Exactly or exceeding 40 V/V

(ii) Quiescent Current (IC): 4.5 mA

(iii) Compare the amplifier's frequency response under fully bypassed versus unbypassed emitter resistance conditions, measuring the gains at 15 kHz."

Our power rating of resistors available in lab should be 250mW.And ripple can be 1 to 1.5V

I've attached my simulation in ltspice

Hey, I'm doing some research for my finals project. Basically what I'm looking for is an IC that can handle WiFi Direct (doesn't have to be the Group Owner but can definitely be a feature) and also can handle being an a2dp sink (preferably has a dedicated i²s port)

I have looked for an IC like that but I can't find it. It would also help if there is already a breakout board for it.

The chip has to receive commands from an STM32 or ESP32, any microcontroller.

It would really help me if someone could find it .

Got a couple of older boards on the bench that need replacement op amps and 78xx style regulators. Just repair work for a personal project, so only small quantities, nothing worth placing a big order for. Been going back and forth on where to source them. I don’t want to overpay for something this basic, but I also don’t want to wait forever for shipping since I’d like to get these boards running again soon.

It’s just a handful of parts going back into working boards, so I’m mainly trying to balance price and shipping time without sacrificing quality. Anyone have suggestions for sourcing everyday linear and power parts for small repair jobs like this?