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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.

Filters (None)
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Power Line Filter - Loaction of Cy and CMC

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, th...

3 answers  ·  posted 19d ago by 2kind‭  ·  edited 7d ago by Lundin‭

71%
+3 −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 20d ago by 2kind‭  ·  last activity 8d 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 9d ago by yefj‭  ·  closed as duplicate 9d ago by Olin Lathrop‭

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+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 9d ago by yefj‭  ·  closed 9d ago by Olin Lathrop‭

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+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 12d ago by kadamrohan16‭  ·  last activity 11d 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 12d ago by yefj‭  ·  closed 12d 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 15d ago by Elleanor Lopez‭  ·  last activity 14d ago by Olin Lathrop‭

71%
+3 −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 25d ago by misk94555‭  ·  edited 18d 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 6mo ago by Kalel‭  ·  last activity 18d 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 28d ago by newbie‭  ·  last activity 28d 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 28d ago by newbie‭  ·  last activity 28d 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 1mo ago by losdox‭  ·  edited 1mo 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 1mo ago by mohammadsdtmnd‭  ·  edited 1mo ago by mohammadsdtmnd‭

42%
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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 2mo ago by Conrado‭  ·  edited 2mo ago by Nick Alexeev‭

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+0 −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 2mo ago by misk94555‭  ·  edited 2mo ago by misk94555‭

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+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 2mo ago by aditya98‭  ·  last activity 2mo 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 2mo ago by Elleanor Lopez‭  ·  last activity 2mo ago by Olin Lathrop‭

60%
+1 −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 2mo ago by Mu3‭  ·  last activity 2mo ago by Olin Lathrop‭

66%
+4 −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 2mo ago by Pete W‭  ·  edited 2mo ago by Pete W‭

83%
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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 3mo ago by misk94555‭  ·  last activity 2mo ago by Conrado‭

PCB
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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 2mo ago by Lundin‭  ·  last activity 2mo 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 2mo ago by DeadMouse‭  ·  last activity 2mo 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 2mo ago by kadamrohan16‭  ·  last activity 2mo 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 3mo ago by Chupacabras‭  ·  last activity 3mo 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 3mo ago by mohammadsdtmnd‭  ·  closed 3mo ago by Olin Lathrop‭

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+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 3mo ago by Monica Cellio‭  ·  last activity 3mo 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 4mo ago by dekker‭  ·  last activity 3mo ago by TonyStewart‭

66%
+2 −0
What type of button is this on a remote control

The remote control of my TV has two kinds of buttons. There are "normal" ones for the digits etc. which work by bringing a conductive material on the underside of the button in contact with the boa...

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

75%
+4 −0
High voltage transformer design

Suppose I have a planar PCB transformer. The primary and secondary coils are printed on different PCBs. The core is inserted through these PCBs to link the two coils. The primary is at a low voltag...

2 answers  ·  posted 4mo ago by jonathan_the_seagull‭  ·  last activity 4mo ago by Andy aka‭

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+4 −0
Level shifting of a 3 state logic pin

I want to design a simple battery charger using MCP73831/2. This chip has a 3-State state pin according to the table below: I have a 3.3V MCU and I want to connect this pin to a GPIO. The MCU is...

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

75%
+4 −0
Most reliable galvanic isolation technology for extreme EMI environments?

I'm working on another project with extreme EMC requirements as per various notorious military EMC standards. Civilian product but for military use, and as such subject to the toughest levels of co...

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

50%
+2 −2
Weird grounding on a vintage hifi sideboard

I got a vintage ('64) hifi sideboard for Christmas! It's super awesome. However, I don't understand the grounding. It has two female inputs on the backside that are labeled as "Grounding". There w...

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

75%
+4 −0
Speed of EM waves from the point of view of an electrical engineer

An important formula in physics is one that relates the speed of an EM wave (c for instance) with the magnetic permeability and electric permittivity of the medium. In short: - $$c = \dfrac{1}{\sq...

1 answer  ·  posted 5mo ago by Andy aka‭  ·  edited 5mo ago by Andy aka‭

71%
+3 −0
Transformer design for a Series Resonant Converter

I am determining the Area-Product of the core required for a transformer to be used within a series resonant converter. The specifications are as follows: Switching frequency = 400 kHz Primary ...

1 answer  ·  posted 5mo ago by jonathan_the_seagull‭  ·  last activity 5mo ago by Andy aka‭

60%
+1 −0
CAN BUS monitoring with a LED

Hi, how can I use can bus monitoring through a simple led without disturbing the can line , I started with a diagram found on this forum, I need your help to correct where necessary, I want to use...

3 answers  ·  posted 5mo ago by Marian_20099‭  ·  last activity 5mo ago by Lundin‭

57%
+2 −1
Can I make an AC inductor (reactor) rated 75mH 40A from a 3-phase induction motor?

For my test bench I need an inductor (aka "reactor") that meets the requirements below. I have tried to purchase it outright as a made-up item, or the parts to make it (core and windings), but have...

2 answers  ·  posted 7mo ago by Fabio Barone‭  ·  last activity 5mo ago by TonyStewart‭

50%
+0 −0
Converting 5V to ±12V

I would like to convert 5V rail I have on PCB to ±12V. Existing solution is using boost converter 5V to 12V, and a buck for 5V to -12V. This feels bulky for what it's needed - here are the requirem...

2 answers  ·  posted 6mo ago by 2kind‭  ·  last activity 6mo ago by H_H‭

77%
+5 −0
Ceramic capacitor "memory" effect?

I have run into an interesting phenomenon related to ceramic capacitors. This question is part of the effort to understand the issue, and eventually work around it. But first, some background of ...

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

60%
+1 −0
Noise from oscillator on top layer to clock on bottom layer with VCC & GND layers between

What effect does an oscillator potentially have on a SPI clk signal if the oscillator is on the top layer, with GND and VCC layer in between on a four layer board. I know running it on the same lay...

2 answers  ·  posted 6mo ago by Hawk2020‭  ·  last activity 6mo ago by Nick Alexeev‭

71%
+3 −0
What fabrication process is being used for jellybean parts

I want to know why the top-of-the-line CPUs and GPUs from Intel, NVIDIA, and AMD are all bragging about the fabrication process (7nm and 5nm) and trying to be consistently smaller. At the same tim...

3 answers  ·  posted 6mo ago by dekker‭  ·  last activity 6mo ago by TonyStewart‭

62%
+3 −1
When and where to use vias in an IC design layout

I am learning IC design layouts using Cadence Virtuoso and now I got stuck with the concept of using vias. The question is when and where to use it? I am attaching the schematic of my inverter tuto...

1 answer  ·  posted 7mo ago by aditya98‭  ·  last activity 7mo ago by ErnestoG‭

60%
+1 −0
IEPE Sensor Internal Circuit

Based on reading the All About Circuits article on IEPE sensors there are two general types of circuits integrated into this class of sensors: voltage amplifier and charge amplifier. This question...

0 answers  ·  posted 7mo ago by DavidE‭

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+4 −0
Driving LED with NPN transistor from I/O pin

I'm trying to understand a circuit for driving a LED found on a board I purchased. Below is the circuit driven by an I/O pin (HS2) of a small 3.3V processor. The HS2 pin is driven by the I/O wi...

4 answers  ·  posted 4y ago by eric‭  ·  last activity 8mo ago by TonyStewart‭

60%
+1 −0
derating MLCC ripple current for transient current spikes

This graph - MLCC temperature rise vs ripple current RMS & frequency If I had a 10 us current spike every 100 000 us (akin to a half-sine wave and then the rest of 9999 sine waves missing), ...

2 answers  ·  posted 8mo ago by kellogs‭  ·  last activity 8mo ago by TonyStewart‭

66%
+2 −0
Will shorting a lithium ion battery cause an explosion?

I've seen batteries get shorted a few times. They heat up, and obviously the battery is not useful after, but I've never seen them explode or catch fire. I've read reports of some batteries catchin...

3 answers  ·  posted 8mo ago by matthewsnyder‭  ·  last activity 8mo ago by TonyStewart‭

75%
+4 −0
What are some best practices for library management?

Most CAD packages use a "symbol" and "footprint" library approach when it comes to designing schematics and PCBs. Some (like recent versions of Altium) have "component" libraries where symbols and ...

3 answers  ·  posted 8mo ago by Mu3‭  ·  last activity 8mo ago by H_H‭

72%
+6 −1
How to protect RF switches from ESD?

Assume that I have some generic antenna connector, followed by a pi-filter/50ohm impedance matching components, then a DC blocking cap (as per the RF switch recommendations) and then a RF switch fo...

4 answers  ·  posted 2y ago by Lundin‭  ·  last activity 8mo ago by Nick Alexeev‭

RF
71%
+3 −0
Burned Source Driver - Noise Spikes from Relay Coil

I am trying to figure out what is causing an Allegro A2982 source driver to burn up. The source driver (A2982) is connected to the coil of a Panasonic TXS2-9V relay. The source driver and coil ar...

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

77%
+5 −0
Soft-start circuit behaviour

Let's take a soft-start circuit that looks like this: To my understanding, the function can be described as follows: C1 charges to open the gate. Value of C1 will dictate the soft-start delay...

1 answer  ·  posted 9mo ago by Mu3‭  ·  last activity 8mo ago by Olin Lathrop‭

50%
+1 −1
Confusion about channel capacity definition and units

Why can the channel capacity C of the additive white gaussion noise (AWGN) channel be denoted in different ways and how do they relate to each other? Examples: C = (1/2) * log2(1 + SNR) [bit?] ...

0 answers  ·  posted 9mo ago by daniel_s‭  ·  reopened 8mo ago by Olin Lathrop‭