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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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60%
+1 −0
Cutoff frequency of single phase transmission line

Signals with frequency above the cutoff frequency of a transmission line cannot be transmitted through the transmission line. But how can I calculate the cutoff frequency of a single phase transm...

0 answers  ·  posted 2y ago by MissMulan‭  ·  reopened 2y ago by Olin Lathrop‭

33%
+0 −2
Re model of transistor is the same in 2 different configuration

I was studying the Re model of a transistor: But the Re model for 2 different configurations (common emitter and common base )turns out to be the same! I don't know why I am really confused.How...

2 answers  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by LvW‭

66%
+4 −1
PCB ground planes with isolated voltage

I have designed a PCB that I need to work in which a microcontroller drives a 24 V brushed motor. The input power to the board is 24 V, this is then lowered to 5 V by a step down converter, and thi...

3 answers  ·  posted 2y ago by Alinik‭  ·  last activity 2y ago by KalleMP‭

77%
+5 −0
Unexpected impedance spike when paralleling capacitors

I was watching a video from EEVBLOG about bypass capacitors, and he presented a theory that randomly connecting different values of capacitors in parallel can create unexpected impedance spikes: ...

3 answers  ·  posted 2y ago by Elleanor Lopez‭  ·  last activity 2y ago by Andy aka‭

50%
+3 −3
What reactance actually is?

I saw that equation of reactance is written like this $$I=\frac{V}{|R+X_L j|}$$ $$I=\frac{V}{|R-X_c j|}$$ When there's capacitor and inductor in a single circuit then it is written like : $$I=\...

4 answers  ·  posted 2y ago by deleted user  ·  last activity 2y ago by Andy aka‭

80%
+6 −0
DAC controlled high side current source.

I'm designing a high side current source that can be controlled with a Digital-to-analog and can source up to 100mA with voltage supply up to 36V. By high side I mean one side of load will be alwa...

1 answer  ·  posted 2y ago by DeadMouse‭  ·  last activity 2y ago by Olin Lathrop‭

66%
+4 −1
How to choose the right value for input voltage ripple of an SMPS?

Which important system design parameters need to be locked in order to estimate the maximum allowable level of the input voltage ripple of an SMPS? I have encountered ballpark figures of <1%, &...

1 answer  ·  posted 2y ago by 2kind‭  ·  last activity 2y ago by Olin Lathrop‭

77%
+5 −0
Press fit PCB receptacle for plated holes (Marked for non-plated holes)

I saw that this PCB socket: Is marked as pressfit for non-plated holes. However, can it be used with plated holes as well, or will it damage the plating inside?

1 answer  ·  posted 2y ago by Wilkins Ticklebum‭  ·  last activity 2y ago by Olin Lathrop‭

PCB
50%
+2 −2
Inductance vs frequency

Suppose we have a sine signal applied to a inductive load. Is the inductance of the load changed if the frequency of the signal is changed?

3 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 2y ago by coquelicot‭

83%
+8 −0
How long does it take for energy to propagate in a circuit?

The premise In a recent video by the pop-sci channel Veritasium, the concept of the flow of electricity and energy transmission in a circuit was discussed. In that video a thought experiment is pr...

5 answers  ·  posted 3y ago by Mu3‭  ·  last activity 2y ago by coquelicot‭

77%
+5 −0
Why are there more N type than P type MOSFETs?

I was looking at different transistors, especially MOSFETS and I saw that N type MOSFETs seem to be way more popular to be used in circuit design. Is there a reason for that, or am I mistaken?

2 answers  ·  posted 2y ago by crusadEEr‭  ·  last activity 2y ago by Olin Lathrop‭

33%
+0 −2
What happened to my headphones? [closed]

I recently started working at a construction office in another country. I usually listen to music when working, and I saw a headphone jack in the wall, so I thought it is radio or something, I plug...

0 answers  ·  posted 2y ago by Headphone Jackson‭  ·  closed 2y ago by Olin Lathrop‭

57%
+2 −1
Choosing Y value in photoresistor graph

I have designed a graph of the current in a photoresistor related to the brightness of light which hits the photoresistor. Our professor told us that it is more correct to draw the Current/Brigh...

1 answer  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by Olin Lathrop‭

80%
+6 −0
Standardized schematic/layout file formats for PCB CAD tools?

As we know there exists numerous different kinds of PCB CAD software. The big ones seem to be Eagle, KiCAD, Altium, OrCAD, Solidworks, DesignSpark and probably a few more. When it comes to mechani...

1 answer  ·  posted 2y ago by Lundin‭  ·  last activity 2y ago by Olin Lathrop‭

80%
+6 −0
Location of AGC in a superheterodyne RX chain

RF novice here. If using a superheterodyne receiver for the purpose of FM/FSK modulated signals, I'm wondering if the location of an optional automatic gain control (AGC) circuit is always placed o...

0 answers  ·  posted 2y ago by Lundin‭

80%
+6 −0
How do I design a flyback converter? What are the basics I should know?

I need to design a simple flyback converter like this: - I want to control duty cycle from another circuit such as an MCU but, I'm unsure how to proceed. My requirements are: - Input voltage 125 ...

2 answers  ·  posted 4y ago by Andy aka‭  ·  last activity 2y ago by Andy aka‭

77%
+5 −0
Why do large RAM chips not have a serial interface?

I have a PIC32MZ2048ECG064, a 64-pin 32-bit microcontroller with 512kB RAM. This is not enough for my purposes, I need to extend it by at least 32MB, preferably 64 or 128. I believe this means I ca...

0 answers  ·  posted 3y ago by Keelan‭

22%
+0 −5
Why won't this Globe Electric Dimmable LED securely fit my IKEA November Lamp? [closed]

On the LEFT is what I just bought today — Globe Electric 4W (40W Equivalent) Daylight (5000K) Dimmable LED Light Bulb, G9 Bi-Pin Base, 400 Lumens, 15,000 H. Here's Globe Electric's Dimmer Compatibi...

0 answers  ·  posted 3y ago by TextKit‭  ·  closed 3y ago by Olin Lathrop‭

77%
+5 −0
PCB Copper Layer Spacing & Voltage Rating

One standard used for spacing conductors based on voltage is the IPC-2221. This standard differentiates spacing requirements for inner and outer conductors. Does the IPC minimum separation betwee...

1 answer  ·  posted 3y ago by DavidE‭  ·  edited 3y ago by Lundin‭

77%
+5 −0
Design considerations for a differential pair

Differential pairs, such as for ethernet or a CAN bus, can be designed to be loosely coupled or tightly coupled. For a loosely coupled differential pair, the odd-mode and even-mode impedances are ...

1 answer  ·  posted 3y ago by DavidE‭  ·  last activity 3y ago by Olin Lathrop‭

75%
+4 −0
Via on pad: acceptable or not?

I am designing a PCB with somewhat limited space. To save space, I am placing some vias on component pads. However, I am not sure if this is a good practice in PCB design. As far as I understand, t...

1 answer  ·  posted 3y ago by Mu3‭  ·  last activity 3y ago by Olin Lathrop‭

28%
+0 −3
Phase shift between phase and line quantities [closed]

In a 3 phase Star source-Star load circuit the phase voltage has different phase than line voltage and in a 3 phase Delta source-Delta load circuit the phase current has different phase than the li...

0 answers  ·  posted 3y ago by MissMulan‭  ·  closed 3y ago by Olin Lathrop‭

42%
+1 −2
Splitting of message inside the layers [closed]

Assume a app generates a message (stack on computer).Each layer of the sending entity will put then control information in the data depending on the protocol and transmit the data to the next lowe...

0 answers  ·  posted 3y ago by MissMulan‭  ·  closed 3y ago by Nick Alexeev‭

86%
+11 −0
208VAC triple-phase to single-phase conversion

The question: Is there a way to convert from triple-phase 208VAC to single-phase 208VAC? Background: Hi everyone, I am stuck on a project I'm working on. I'd like to convert 208VAC (three phase,...

2 answers  ·  posted 3y ago by cosined‭  ·  last activity 3y ago by Andy aka‭

75%
+4 −0
ESD USB Shield Connection & Filtering

I have a handheld ARM Cortex M based device, which has a USB input port. The product is battery powered and there is no metal chassis. We are going through CE testing, and are having ESD issues a...

4 answers  ·  posted 4y ago by leroy105‭  ·  last activity 3y ago by Pete W‭

50%
+0 −0
What is minimum resolution here?

In this datasheet it says that the minimum resolution is 0.1uA for the 10mA range.What is this minimum resolution?Is it the sensitivity of the multimeter for the 10mA range?

1 answer  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by dsr‭

66%
+2 −0
Resistance of digital ampmeter

Can we find the internal resistance of a multimeter ,when we use the multimeter like a ampmeter, from its datasheet? I am trying to find the internal resistance of IDM 505 and I went to the datash...

2 answers  ·  posted 3y ago by MissMulan‭  ·  edited 3y ago by Canina‭

66%
+4 −1
What is sacrificed when buying cheaper oscilloscope probes (of same BW/cap/R/gain)

I'm wondering if there are particular aspects of an oscilloscope probe's performance that tend to suffer, or failure points to look out for, if/when buying lower-end makes of oscilloscope probes (l...

1 answer  ·  posted 3y ago by Pete W‭  ·  last activity 3y ago by Olin Lathrop‭

81%
+7 −0
Low-frequency PWM-controlled Mosfet heater circuit

The circuit above is used to control a 240W ceramic heater by means of a PWM signal at 30Hz, generated by a microcontroller, with 5V logic. The input is a standard 280W AC-DC external power adapt...

2 answers  ·  posted 3y ago by francesco‭  ·  last activity 3y ago by Pete W‭

50%
+1 −1
MOSFET not turning completely off

Hello everyone, I have a simple circuit in which I control some LEDs via an MCU and DMG2302UK ( N-channel MOSFET ) The EN pin is connected to an MCU gpio pin that works at 3.3V. The circuit wo...

1 answer  ·  posted 3y ago by AhmedMobarez‭  ·  last activity 3y ago by Olin Lathrop‭

60%
+1 −0
Confusion with Wikipedia article on multivibrator circuit [closed]

A while ago I made a question about the monostable multivibrator .Lets get a picture of it: When switch is closed it enters its unstable state and it eventually returns to the stable state Howe...

0 answers  ·  posted 3y ago by MissMulan‭  ·  closed 3y ago by Olin Lathrop‭

50%
+0 −0
Capacitors of voltage regulators [closed]

Assuming we have a voltage regulator : Why do we have to ground Vin and Vout using 2 capacitors just like that?Co could be to provide a low resistance path to GND at high frequencies but what is...

0 answers  ·  posted 3y ago by MissMulan‭  ·  closed 3y ago by Olin Lathrop‭

28%
+0 −3
Find feedback of circuit

I have this circuit: I think that R3 acts like a feedback path from the output to the input.However I am not sure what will happen if I change the value from 100Ohms to lets say 1kOhms. I have ...

2 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by LvW‭

71%
+3 −0
Most correct term for radio switching noise?

I'm wondering what's the most correct term (if any) to use for "switching noise" of a radio transceiver? By that I mean the spikes that originate from turning the power amp on/off while switching b...

1 answer  ·  posted 3y ago by Lundin‭  ·  last activity 3y ago by Olin Lathrop‭

37%
+1 −3
What is the popular 12 V DC jack connector?

I'm designing a PCB for a project. 12 volt input power supply is provided externally, so the user will buy a power adapter, so putting a popular DC jack on the PCB is the best choice.

2 answers  ·  posted 3y ago by vigneshtnj‭  ·  last activity 3y ago by DavidCary‭

75%
+4 −0
CAN "split" pin, bus termination and common mode stabilization

Modern CAN transceivers like MCP2561FD that support CAN FD with high baudrates come with an optional feature called SPLIT, which is to my understanding a reference voltage output pin used to give a...

1 answer  ·  posted 3y ago by Lundin‭  ·  last activity 3y ago by Olin Lathrop‭

50%
+1 −1
Driving PMSM machine as an AC induction machine

Is it possible to drive a PMSM motor - here I am referring to an AC motor with permanent magnets(stator wounded, rotor with PM) - in a way that there is no externally mounted rotor position sensor(...

1 answer  ·  posted 3y ago by 2kind‭  ·  last activity 3y ago by Olin Lathrop‭

62%
+3 −1
Help with differential to single ended voltage converter

Hello I don't understand how this differential to single-ended voltage converter can work. What I don't understand is why we place a current mirror(a current mirror copies the current flowing thr...

3 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by Circuit fantasist‭

50%
+1 −1
Change of pins in monostable multivibrator

In monostable multivibrators we use a trigger signal applied to the base of the transistor which is usually off to enter the astable region Can we instead have a pin which is connected directly ...

2 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by Circuit fantasist‭

33%
+0 −2
Capacitance of inductor

What is a typical value for capacitance of a real inductor? Does this internal capacitance exist only under AC and not DC?

1 answer  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by Olin Lathrop‭

66%
+2 −0
MOSFET differential to single ended converter intuition

How does the differential to single ended converter work? In order for the circuit to work, Q1 and Q3 must be in the saturation region and depending on the voltage inputs, one of Q2 and Q4 will be...

1 answer  ·  posted 3y ago by MissMulan‭  ·  edited 3y ago by Peter Mortensen‭

50%
+1 −1
Coupling of inductors

Which will be the total series inductance?

2 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by Andy aka‭

28%
+0 −3
Current and voltage of inductor

How do I find the current through the inductor and the voltage of the inductor after the switch is closed?

2 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by MissMulan‭

60%
+1 −0
Voltage and Current of capacitor

How do I find the voltage of the capacitor and the current through the capacitor after the switch is closed?

1 answer  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by MissMulan‭

60%
+1 −0
SPI modes difference

What is a difference between SPI stream and memory mapped SPI? PS SPI is a peripheral.

2 answers  ·  posted 3y ago by FrankLEE‭  ·  last activity 3y ago by DavidCary‭

SPI
75%
+4 −0
Thermal relief for through-hole on multi-layer PCB

When using through-hole ("THR") connectors on a multi-layer PCB, I frequently notice problems with the ground pins, when these are connected to the ground plane(s) through various "thermal relief" ...

1 answer  ·  posted 3y ago by Lundin‭  ·  edited 3y ago by Nick Alexeev‭

71%
+3 −0
Type II compensation network for a non-ideal transconductance amplifier

I am designing a DC/DC converter in the control loop of which a transconductance amplifier (OTA) is used. This part of circuit looks like this: To determine the needed characteristics, I am usin...

1 answer  ·  posted 3y ago by Mu3‭  ·  edited 3y ago by Mu3‭

75%
+4 −0
What is the difference between emitter and collector of a transistor?

In all descriptions of how (non-FET) transistors work I've seen, there is an inherent symmetry: There's either an n-doped layer between two p-doped, or a p-doped between two n-doped, and the descri...

2 answers  ·  posted 3y ago by celtschk‭  ·  last activity 3y ago by Olin Lathrop‭

66%
+2 −0
$Q$ and $\overline{Q}$ in bistable multivibrator

In this bistable multivibrator which is $Q$ and which is $\overline{Q}$?

1 answer  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by Olin Lathrop‭

66%
+4 −1
Motor Controller - What might be the purpose of these resistors?

I was looking at the video of the Tesla Model 3 motor controller(400VDC, 500A) disassembly and noticed a resistor network as in the picture below. They are 2k resistors(SMD code 202). See the pic...

4 answers  ·  posted 3y ago by 2kind‭  ·  last activity 3y ago by DSI‭