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Q&A

General Q&A about the design and function of electronic systems, electric power systems and infrastructure, their theory, and tools specific to those fields. Read these guidelines before posting.

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66%
+2 −0
OPA2211 datasheet error

Looking at Texas Instruments opamp OPA2211it mentions GBW of 80MHz at a gain of 100, and 45MHz at gain of 1: Looking at the bandwidth graph from Figure 10 in datasheet: It looks like 80MHz is...

3 answers  ·  posted 9d ago by Elleanor Lopez‭  ·  last activity 7d ago by Elleanor Lopez‭

66%
+2 −0
How does JFET biasing work in a 2-terminal electret condenser microphone?

I’m trying to understand the biasing of a 2-terminal electret condenser microphone.  The inner workings of a 2-terminal electret microphone are always drawn without a resistor at the JFET source.  ...

2 answers  ·  posted 13d ago by misk94555‭  ·  last activity 12d ago by Andy aka‭

57%
+2 −1
Opto-coupler, slow turn off

I have an opto-coupler circuit where is very slow turn off. I can't figure out what is the cause of this problem. It's for UART isolation, with speed 9600 baud. Datasheet: EL357NC Do I have som...

2 answers  ·  posted 26d ago by Chupacabras‭  ·  last activity 25d ago by Chupacabras‭

57%
+2 −1
Why did the battery blow out?

I have a bed for which the headrest can be adjusted. There are 2 separate power inputs for each side like in the picture: In addition, there is a set of 9V batteries on each side, presumably for...

2 answers  ·  posted 1mo ago by Elleanor Lopez‭  ·  last activity 1mo ago by absurdus‭

50%
+1 −1
Is it possible to build a passive many hosts to a single disk SATA splitter?

I don't find any of such cables, and the discussions on the web revolve around SATA being point-to-point and not designed for networked or shared storage. However, if one'd build a cable that is j...

1 answer  ·  posted 2mo ago by mavavilj‭  ·  last activity 1mo ago by absurdus‭

66%
+2 −0
Which transistor type to use for charge shuttle, as part of an active charging circuit?

Hi All! I've been looking at how to perform active battery balancing, and I'm currently struggling to understand which type of transistor to use to act as the switch for the "balancing capacitor"....

2 answers  ·  posted 1mo ago by Boolean‭  ·  last activity 1mo ago by absurdus‭

50%
+1 −1
Analysis of LC circuit using intuition

This problem investigates the behavior of the voltage across the capacitor in response to a step input: - I am asked to find the voltage Vc(t) without the use of differential equations or simula...

2 answers  ·  posted 2mo ago by Carl‭  ·  last activity 1mo ago by Olin Lathrop‭

66%
+2 −0
Connector rated voltage vs IPC-2221B and IEC 62368

Rosenberger 23C25D-40ML5 specifies 500V RMS rating: Looking at the recommended landing pattern you can see that the distance between the signal landing pad and housing of the connector is 0....

1 answer  ·  posted 2mo ago by Elleanor Lopez‭  ·  last activity 2mo ago by Olin Lathrop‭

50%
+1 −1
Issue in Cable Sizing and control cable selection

Hi All, I have a query regarding the cable sizing and motor starting. I have a 200HP motor to feed Low voltage power @480V. The distance between the substation and the motor is 2000m. Voltage dro...

1 answer  ·  posted 2mo ago by AKKIIK‭  ·  last activity 2mo ago by Olin Lathrop‭

40%
+0 −1
What are closest free or low-cost alternatives to software like Ansys PCB modelling? [closed]

What are closest free or low-cost alternatives to software like Ansys PCB modelling? https://www.ansys.com/blog/optimize-your-pcb It's too costly for study purposes. To clarify: I am looking fo...

0 answers  ·  posted 2mo ago by mavavilj‭  ·  closed 2mo ago by Nick Alexeev‭

37%
+1 −3
Do hobbyist slabtop Wi-Fi modifications need to consult FCC regulations?

Do I need to consult FCC regulations in order to modify a laptop's internal WI-FI antennas to a new housing? This is quite common when modifying laptops to "slabtops". For example, one could 3D pr...

2 answers  ·  posted 3mo ago by mavavilj‭  ·  edited 2mo ago by mavavilj‭

60%
+1 −0
What is connector pitch and how to measure it?

When posting identification or general questions related to connectors, integrated circuits or other parts with pins/legs, engineers always speak about something called pitch. What is the meaning ...

1 answer  ·  posted 2mo ago by Lundin‭  ·  last activity 2mo ago by Lundin‭

62%
+3 −1
Having a hard time understanding discrete audio amplifier output stage error corrector circuit

I'm trying to implement a circuit I read about in a book recently, but having a hard time deriving the relationships for the required impedances for error corrector balance. Here is the circuit: ...

0 answers  ·  posted 3mo ago by drinkingcube‭  ·  edited 3mo ago by Nick Alexeev‭

71%
+3 −0
Circuit for earth conductor presence detection

Reading a Tesla Wall Adapter installation manual , their brand of an AC EV charger, chapter about “Ground Assurance” and here is the quote from there: Although the equipment can work with L1 and...

2 answers  ·  posted 4mo ago by 2kind‭  ·  last activity 3mo ago by TonyStewart‭

66%
+2 −0
Are LDOs more efficient than switching regulators in very low currents?

I'm looking for a power supply to power up the VCORE of an mcu. The chip is an STM32 microcontroller (LQFP) and the maximum current it will draw is no more than 150mA. The input will be 3V-5V max...

3 answers  ·  posted 4mo ago by DeadMouse‭  ·  last activity 3mo ago by TonyStewart‭

60%
+1 −0
Purpose of resistance between SENSE/FORCE line of power supply

I am reading through a multi-channel power supply manual and at some point it discusses the ability to chain channels in parallel to increase current output. In the schematic, there is one resisto...

3 answers  ·  posted 3mo ago by dekker‭  ·  last activity 3mo ago by TonyStewart‭

60%
+1 −0
Synchronous FIFO design code review

As a personal project, I have designed a synchronous FIFO in Verilog HDL. But while testing with a testbench, I observed that the FIFO values are flushed out after one clock cycle when read-enable ...

0 answers  ·  posted 3mo ago by aditya98‭

66%
+2 −0
CAN bus open circuit detection

I have a PIC18 and I'm trying to detect whether it is connected on the CAN bus or not. When the PIC is not connected on the bus, and I load the transmit buffers, after setting the TXREQ flag. The ...

1 answer  ·  posted 4mo ago by DeadMouse‭  ·  last activity 4mo ago by Olin Lathrop‭

71%
+3 −0
STM32. What should be done in firmware for VBUS detection through a GPIO pin?

I've got a is self-powered USB device, which means that I have to do VBUS detection. The device is built around STM32G474. Unlike some other STM32s, the STM32G4 don't have a dedicated pin for VBUS...

2 answers  ·  posted 5mo ago by Nick Alexeev‭  ·  last activity 4mo ago by Nick Alexeev‭

66%
+2 −0
How to operate a chip very close to its absolute maximum voltage?

I want to operate a BLE chip at very close to its absolute maximum voltage. The chip is nRF52810 This is intended for a battery powered device and I want to use a 3.6V non-rechargable battery dir...

2 answers  ·  posted 4mo ago by DeadMouse‭  ·  last activity 4mo ago by Lundin‭

62%
+3 −1
Using only ceramic capacitors on an input of an SMPS - unclear advice from manufacturer

I was reading through the datasheet of a boost converter, TPS61023 from TI. In the "Input Capacitor Selection section", they give the following advice: 8.2.2.5 Input Capacitor Selection Multil...

2 answers  ·  posted 5mo ago by Mu3‭  ·  last activity 5mo ago by Nick Alexeev‭

60%
+1 −0
Missing voltage rating

I am looking at this RF connector. I see that insulation resistance and breakdown voltage are specified, but no voltage rating: I have two questions, one functional and one safety. Functionally...

2 answers  ·  posted 5mo ago by Elleanor Lopez‭  ·  last activity 5mo ago by Olin Lathrop‭

50%
+0 −0
ESD Table Earth Bonding Points - Why?

We have ESD tables in the laboratory with Earth Bonding Points: These are directly connected to PE (I measured). It is my understanding that equipment has to be connected to PE directly and ESD m...

1 answer  ·  posted 5mo ago by Elleanor Lopez‭  ·  last activity 5mo ago by Olin Lathrop‭

75%
+4 −0
Power Line Filter. Location of Cy and common mode choke.

A circuit under question: Why are CY capacitors on the source side, and not on the load side? Henry Ott describes this with: Because filter attenuation is a function of impedance mismatch, t...

3 answers  ·  posted 6mo ago by 2kind‭  ·  edited 5mo ago by Nick Alexeev‭

75%
+4 −0
Standardized way of measuring AC line frequency

In a general sinewave as below, is there a "right" way/"standardized" way to measure line frequency - and how do energy meters calculate that? measuring pulse width of half-period, ie. time elap...

3 answers  ·  posted 6mo ago by 2kind‭  ·  last activity 6mo ago by Pete W‭

40%
+0 −1
discharge slope logic (fixed sloppinees question) [duplicate]

Hello, I want to understand the math of the phenomena of capacitor as temporarary means of increasing the current supply. First I have created a current limited voltage source which give me 45V a...

0 answers  ·  posted 6mo ago by yefj‭  ·  closed as duplicate 6mo ago by Olin Lathrop‭

40%
+0 −1
capacitor to overcome voltage source limitation [closed]

Hello,i need to drive 5 mosfets as shown below. Each mosfet draws 15A when the pulse opens the mosfet. My power supply is gives the 48V but only 3.3A,If I understand correctly I need to put very...

0 answers  ·  posted 6mo ago by yefj‭  ·  closed 6mo ago by Olin Lathrop‭

60%
+1 −0
Calculating base voltage of NPN transistor

I'm having trouble using the nodal equations to determine the base voltage Vb1 in the circuit below. I've attempted to write seven equations below, but not able to fit them in entirely. (12-Vx)...

2 answers  ·  posted 6mo ago by kadamrohan16‭  ·  last activity 6mo ago by LvW‭

50%
+0 −0
delay line realistic pulse voltage source of 74ABT04 [closed]

Hello,I want to simulate a delayed pulse going from 74ABT04 to the load which is UCC5304 where load with 400K i think. but my pulse source 74ABT04 is not an idial voltage source as shown in the s...

0 answers  ·  posted 6mo ago by yefj‭  ·  closed 6mo ago by Olin Lathrop‭

60%
+1 −0
Understanding inductive ringing

For my own understanding I tried modelling switching off an inductive load without a freewheeling diode to observe ringing. This is the model I used: 1.) Are the two main components of the reson...

2 answers  ·  posted 6mo ago by Elleanor Lopez‭  ·  last activity 6mo ago by Olin Lathrop‭

75%
+4 −0
What happens when a microSD card is hot-unplugged?

Consider a device with a microSD card. The microcontroller writes to the SD card periodically. The operators have an ability to remove the microSD card at any time (they will be removing it every...

1 answer  ·  posted 6mo ago by misk94555‭  ·  edited 6mo ago by misk94555‭

33%
+0 −2
Beginners Guide To Power Circuit [closed]

I'm Interested In Power Circuit. What Courses/Guidelines To I Need To Properly and Effectively Under Power Circuits??

0 answers  ·  posted 12mo ago by Kalel‭  ·  last activity 6mo ago by Nick Alexeev‭

42%
+1 −2
Flash light frequency and rise time calculation

I was analyzing the design a hazard warning light.The spec of the light turn on off is given below. The flashing-light frequency shall be 90+/-30 times per minute. May I know in this case the...

1 answer  ·  posted 7mo ago by newbie‭  ·  last activity 7mo ago by Olin Lathrop‭

40%
+0 −1
How do we calculate signal rise time from frequency

May I know how to calculate a signals rise time from it's frequency. I found this article for the same. The formula given is Tr = 1/f*π. May I know is this applicable for PWM also.

1 answer  ·  posted 7mo ago by newbie‭  ·  last activity 7mo ago by Olin Lathrop‭

66%
+2 −0
Control logic for mosfet in piezoelectric energy harvesting circuit

I'm working on an energy harvesting circuit known as an in-house harvesting circuit (cc-ih) and would appreciate some guidance on implementing it in Simscape within Simulink. Circuit Description: ...

2 answers  ·  posted 7mo ago by losdox‭  ·  edited 7mo ago by Nick Alexeev‭

33%
+0 −2
LNA layout consideration 1-1000MHz

Mini-circuits LNA PHA-LN13+ has suggested: Eval board Layout Eval Gerber The image took from the Gerber file (3rd ref.) (Though all 3-reference mentioned containing it): There I have som...

0 answers  ·  posted 7mo ago by mohammadsdtmnd‭  ·  edited 7mo ago by mohammadsdtmnd‭

50%
+2 −2
What are these mystery components (one of wire coil, another labeled "100-10L A9")?

I have here an acre-counter or crop counter device like the lykketronic shown below, using two AA batteries. It arrived without working. Upon opening its case, I found that the PCB is missing tw...

2 answers  ·  posted 7mo ago by Conrado‭  ·  edited 7mo ago by Nick Alexeev‭

66%
+2 −0
LED driver with feedback through light. Which feedback topology is better?

I’d like to create a stable IR LED light source. I’ve read that LED efficiency changes with temperature. I’ve seen two designs which used feedback through light to correct the LED temperature dri...

1 answer  ·  posted 8mo ago by misk94555‭  ·  edited 7mo ago by misk94555‭

40%
+0 −1
Determining the output swing, output common-mode range and input common-mode range in a differential amplifer

I am currently learning amplifier design, after constructing the unity gain amplifier(which is a differential-input single-ended-output amplifier) in the unity-gain feedback configuration I have pe...

1 answer  ·  posted 7mo ago by aditya98‭  ·  last activity 7mo ago by Olin Lathrop‭

71%
+3 −0
Step voltage 750kV lines

Some gentlemen decided to throw a hook with wire over 750kV lines in Belarus. They survived, however, I find in interesting to find out why. Assuming the connection to Earth was solid, there would...

1 answer  ·  posted 8mo ago by Elleanor Lopez‭  ·  last activity 8mo ago by Olin Lathrop‭

66%
+2 −0
Regulated charge pump design

I am working with an IC that uses a partially intergrated regulated charge pump. The circuit looks like this: It behaves like a voltage doubler. However, when looking at other regulated charge p...

1 answer  ·  posted 8mo ago by Mu3‭  ·  last activity 8mo ago by Olin Lathrop‭

70%
+5 −1
Humidity specs - is there typical reasoning for lower limit greater than 0?

Question about relative humidity specification for electronics. Industrial automation, indoors, cabinet or instrument enclosure. The failure mechanisms at the upper limit are fairly intuitive. I'm...

0 answers  ·  posted 8mo ago by Pete W‭  ·  edited 8mo ago by Pete W‭

84%
+9 −0
PCB as a wall of an underwater enclosure

Can a circuit board be waterproof enough to form a wall of a waterproof enclosure? Regular PCBs made of FR-4 with solder mask is what I have in mind. But I'm not barring less common PCB materials...

2 answers  ·  posted 9mo ago by misk94555‭  ·  last activity 8mo ago by Conrado‭

PCB
77%
+5 −0
MAX485 transceivers breaking, Pi filter generating spikes?

Problem description & speculation about causes I've having a problem with MAX485 transceivers breaking intermittently, passing our production tests but later failing. The error phenomenon is w...

2 answers  ·  posted 8mo ago by Lundin‭  ·  last activity 8mo ago by Andy aka‭

71%
+3 −0
1-wire interface overvoltage protection

I'm designing a robust 1-wire output for an IoT board. The interface should be able to withstand high voltage. Mainly the same voltage level as the board power supply. That's 12V to 36V DC. The p...

1 answer  ·  posted 8mo ago by DeadMouse‭  ·  last activity 8mo ago by Olin Lathrop‭

60%
+1 −0
MOSFET drain current ringing in saturation region

I benchtested below 0.7A constant current source circuit and observed few cycles of oscillation on drain current. With the help of bode plot analysis , I have managed to reduce the oscillations on ...

2 answers  ·  posted 8mo ago by kadamrohan16‭  ·  last activity 8mo ago by Olin Lathrop‭

66%
+2 −0
Matched transistors

There are circuits that require matched transistors. Whether BJTs or FETs. Like current mirrors, logarithmic amplifiers, etc.. There are some examples: https://www.youtube.com/watch?v=DUlugLSroN8...

1 answer  ·  posted 8mo ago by Chupacabras‭  ·  last activity 8mo ago by Andy aka‭

33%
+0 −2
Implementing local ground theory on PCB power distribution [closed]

I've tryed to implement a local ground concept told by Olin Latrop here : He have told: (What I've perceived)You should not connect every gnd point instantly to gnd plane, since it can inject HF ...

0 answers  ·  posted 9mo ago by mohammadsdtmnd‭  ·  closed 9mo ago by Olin Lathrop‭

66%
+2 −0
Why would a standby UPS fail to power devices when there's no power outage?

I have an ordinary consumer-grade standby UPS with, I believe, ample power for the devices connected to it.[1] It's five years old. For the second time in about a month, I've found my computer po...

4 answers  ·  posted 9mo ago by Monica Cellio‭  ·  last activity 9mo ago by Canina‭

60%
+4 −2
estimation of pogo pin resistance

Is there a scientific way to estimate the resistance of a pogo pin? If it was a solid cylinder or wire one could calculate the resistance: R = ρ × L / A But a pogo pin is hollow inside, the sp...

2 answers  ·  posted 10mo ago by dekker‭  ·  last activity 9mo ago by TonyStewart‭