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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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88%
+13 −0
What is a bootloader, and how would I develop one?

I've heard that a bootloader is code that runs on a microcontroller, and is used to get your application code onto the micro. How does that work? Is there anything special that needs to be done to...

1 answer  ·  posted 3y ago by Olin Lathrop‭  ·  edited 3y ago by Olin Lathrop‭

85%
+10 −0
How to calculate pullup resistor value for pushbutton?

What value pullup resistor should I use for a pushbutton connected to a microcontroller input? I've seen values from 1 kΩ to over 100 kΩ. Some references just say to use 10 kΩ because it's a "goo...

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

85%
+10 −0
Why 3.3V instead of 3V?

Usual values used in doing electronics/power supplies are almost always round numbers: 5V 12V 28V 48V 60V I understand that in some cases ICs are built to accept the voltage directly comi...

4 answers  ·  posted 2y ago by 2kind‭  ·  last activity 1mo ago by TonyStewart‭

85%
+10 −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 2y ago by cosined‭  ·  last activity 2y ago by Andy aka‭

84%
+9 −0
Flyback transformer with Intrinsic Safety

I have no experience designing for Intrinsic Safety (IS), but need to do that now. I have read thru IEC 60079-11, which seems to be the relevant standard for my purposes. The board I need to desi...

4 answers  ·  posted 2y ago by Olin Lathrop‭  ·  last activity 3mo ago by Lorenzo Donati‭

84%
+9 −0
Why do DC/DC switching controllers seem to favour the buck-boost topology over similar ones like Cuk, SEPIC and Zeta?

I am looking at various DC/DC converter topologies for a power system I am designing. The most suitable topology for me is one that can perform both step-up and step-down functions, so I am looking...

2 answers  ·  posted 2y ago by Mu3‭  ·  edited 2mo ago by Lorenzo Donati‭

83%
+8 −0
Rules and guidelines for drawing schematics?

We see schematics of varying quality and conventions. What is good and bad? What are the rules and conventions for drawing good schematics? What matters? What doesn't? This question is about sch...

1 answer  ·  posted 3y ago by Olin Lathrop‭  ·  last activity 11mo ago by Olin Lathrop‭

83%
+8 −0
Is ESD overhyped?

I have seen many engineers talk about ESD protection but I had never seen its effects myself. I made many small DIY projects and I have used bare hands to touch ICs and their pins,but nothing got d...

10 answers  ·  posted 3y ago by aditya98‭  ·  last activity 2mo ago by rdtsc‭

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 2y ago by Mu3‭  ·  last activity 1y ago by coquelicot‭

83%
+8 −0
Technique to reset pulse transformer core quickly

I am analysing a pulse transformer which is required to transfer below communication protocol pulse from primary to the secondary side. The pulse duration is 32 μs and off time available to reset t...

2 answers  ·  posted 1y ago by kadamrohan16‭  ·  edited 2mo ago by Lorenzo Donati‭

81%
+7 −0
How to access a hardware register from firmware?

When writing firmware in C for a microcontroller, how can I directly access a memory location such as a hardware peripheral register, given its absolute address? Is there a way to do this safely an...

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

81%
+7 −0
High Speed Design - Which grounding strategy to choose?

Although I have done multiple PCB designs which passed FCC and CE equivalents using the MCU's/Multiple MCU's, I have a doubt about how to approach the high speed design using FPGA SoC - main thing ...

1 answer  ·  posted 3y ago by 2kind‭  ·  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 2y ago by francesco‭  ·  last activity 2y ago by Pete W‭

81%
+7 −0
When do I need to put anti-aliasing filter in front of SAR ADC?

Signal characteristics are: 0 to 3.3V span 0 to 100Hz range( there will be noise superposed on top with unknown characteristics) Output resistance Rout=4700 ohm I want to sample that with a...

2 answers  ·  posted 1y ago by 2kind‭  ·  edited 2mo ago by Lorenzo Donati‭

80%
+6 −0
What is this fourth connection in NMOS device?

I know that in transistors there is base, collector and emitter, and in FETs there is gate, drain and source, but what is the fourth grounded connection opposite the gate in this NMOS circuit?

1 answer  ·  posted 1y ago by NMOS lover‭  ·  edited 2mo ago by Lorenzo Donati‭

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 1y ago by Lundin‭

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 1y ago by Lundin‭  ·  last activity 1y ago by Olin Lathrop‭

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 1y ago by DeadMouse‭  ·  last activity 1y ago by Olin Lathrop‭

80%
+10 −1
Why are some PCB design software programs considered to be 'hobbyist' programs?

Recently I have heard this opinion from experienced engineers when discussing PCB design software. The common opinion was that Allegro and Altium are supposedly professional programs whereas Eagle ...

3 answers  ·  posted 1y ago by Wilkins Ticklebum‭  ·  last activity 2mo ago by Sclrx‭

80%
+6 −0
DC offset correction loop (DC servo loop). What's its advantage, compared to a high-pass RC filter?

Once in a while in literature I see a DC offset subtraction loop. Here are a few more examples. DC servo loop removes a DC offset after an op-amp. DC servo loop removes DC current from a photo...

2 answers  ·  posted 5mo ago by misk94555‭  ·  edited 2mo ago by misk94555‭

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 3y ago by Andy aka‭  ·  last activity 1y ago by Andy aka‭

80%
+6 −0
Should I connect signal reference and chassis ground in a battery powered application?

Hello. I have a grounding problem on my acquisition system. I have read many articles, app notes and whatever but still could not find a convincing solution for the topic. The acquisition system is...

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

77%
+5 −0
Can you call an IC pin 'N.C' if it has hidden functionality?

The particular IC I ran into this issue with was DS3231 RTC. The pin configuration shows: However, the datasheet specifies To my knowledge, 'N.C' appears on ICs when it is decided to use a cer...

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

IC
77%
+5 −0
What are the most common causes of CAN bus communication errors?

I can't get my CAN bus application (ISO 11898-2, classic "high speed CAN") working and I'm receiving various CAN error frames. These error frames manifest themselves as sequences of 6 bits with my ...

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

77%
+5 −0
Is it possible to use two zener diodes in series back to back to replace a diac?

I've accidentally burnt my dimmer with a short. It is a common dimmer with a triac/diac/pot of the simplest configuration (the triac is a BTA16). After replacing the triac, this still does not work...

2 answers  ·  posted 3y ago by coquelicot‭  ·  edited 2mo ago by Lorenzo Donati‭

77%
+5 −0
Substituting multiple lower voltage resistors for a high voltage resistor

Certain high voltage resistors are fairly hard to get, such as the HVR37 series from Vishay. I'm looking at redesigning a board that produces 1000V via a transformer, but I want to use parts that ...

1 answer  ·  posted 3y ago by TimH‭  ·  edited 2mo ago by Lorenzo Donati‭

77%
+5 −0
What should be considered when picking a flyback diode?

Which are the parameters I should looking for when picking a flyback diode to be placed across a generic coil, such as a relay? That is: a coil with plain on/off functionality, for example a 24VDC ...

2 answers  ·  posted 2y ago by Lundin‭  ·  edited 2mo ago by Lorenzo Donati‭

77%
+5 −0
Siglent1104 oscilloscope channels lagging

First I noticed that clock begins before chipselect gets pulled low on SPI. After eliminating potential sources I started to suspect the scope. I connected all 4 channels to function generator at d...

3 answers  ·  posted 1y ago by Elleanor Lopez‭  ·  last activity 1y ago by Elleanor Lopez‭

77%
+5 −0
Capacitor ESR vs. Impedance

One of the ceramic capacitors that I've found(link to the capacitor) specifies the following characteristics at 10 kHz: The difference in value is quite significant, almost 100 fold. Which grap...

3 answers  ·  posted 2y ago by 2kind‭  ·  last activity 2y ago by TonyStewart‭

77%
+5 −0
Is there a way to reliably measure antenna return loss outside a lab?

Assume I'm a complete beginner at RF. Is there a way to measure return loss of an antenna, in such a manner that I can reliably reproduce the measurement later on? What I'm talking about is produ...

2 answers  ·  posted 2y ago by Lundin‭  ·  last activity 1y ago by TonyStewart‭

77%
+5 −0
What effect will extreme temperatures have on characteristic impedance of a wire?

My scenario is this: radio equipment controlling an overhead crane inside a steel mill. Specifically it is used for transporting melting pots. With the current, unfortunate installation, the antenn...

2 answers  ·  posted 1y ago by Lundin‭  ·  last activity 2mo ago by Lorenzo Donati‭

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 2y ago by DavidE‭  ·  last activity 2y ago by Olin Lathrop‭

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 1y ago by Elleanor Lopez‭  ·  last activity 1y ago by Andy aka‭

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 2y ago by DavidE‭  ·  edited 2y ago by Lundin‭

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 1y ago by Keelan‭

77%
+5 −0
PNP Darlington pair as a current limiter

I am trying to analyse what is controlling the load current in the below Darlington configuration. Is it the base current of transistor Q3 which is controlling current through R14 / emitter curr...

1 answer  ·  posted 1y ago by kadamrohan16‭  ·  edited 2mo ago by Lorenzo Donati‭

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 1y ago by crusadEEr‭  ·  last activity 1y 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 1y ago by Wilkins Ticklebum‭  ·  last activity 1y ago by Olin Lathrop‭

PCB
77%
+5 −0
Unterminated SPI bus needs expansion board to work properly

I'm supporting a piece of legacy hardware that routes the SPI bus through a set of headers to an expansion board. Since the expansion board doesn't actually use the SPI bus, we simply ignored the ...

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

77%
+5 −0
Ground pour on outer layers on 4-layer PCB

I'm designing a board that contains a cortex-M4 mcu working at 120MHz, and an ethernet bus with a wiznet chip that communicates with SPI. The ethernet chip gives me a phy output that goes directly...

2 answers  ·  posted 3mo ago by DeadMouse‭  ·  edited 2mo ago by Lorenzo Donati‭

77%
+5 −0
Possible stray current corrosion in reinforced concrete

I have a question about stray current corrosion in reinforced concrete. I am working on a project in a parking garage with PV-panels on top of the roof. The ground is directly connected to reinforc...

1 answer  ·  posted 10mo ago by Willem ‭  ·  edited 2mo ago by Lorenzo Donati‭

77%
+5 −0
How to perform initialization of static storage variables in embedded systems?

Whenever declaring a variable in C outside a function at file scope or when specifying it as static, it gets assigned a life time known as static storage duration. Meaning it will be accessible thr...

1 answer  ·  posted 11mo ago by Lundin‭  ·  last activity 3mo ago by Lorenzo Donati‭

77%
+5 −0
What material is used in the tabs of power packages? (TO-220, D2PAK, etc.)

What material is used in the tabs of power packages? (TO-220, D2PAK, etc.) I would assume probably a tin-plated copper alloy, but I can't find a reference. Datasheets don't seem to mention the mat...

1 answer  ·  posted 3mo ago by Jason S‭  ·  last activity 3mo ago by Lorenzo Donati‭

77%
+5 −0
Buck-boost converter fed from split input supply

I have recently finished designing a buck-boost converter for a job that uses a split (+/-) input power supply. Load power is taken equally from both positive and negative input supplies and, the ...

1 answer  ·  posted 12mo ago by Andy aka‭  ·  edited 2mo ago by Lorenzo Donati‭

77%
+5 −0
Low-pass filter after the output DAC in CD players

[Disclaimer. This is not for an academic class. I'm self-studying.] I’m reading an introductory book on DSP for audio and computer music [Steiglitz 1996, ISBN 0-8053-1684-1 p. 287]. One of the ...

4 answers  ·  posted 12mo ago by Nick Alexeev‭  ·  last activity 2mo ago by Lorenzo Donati‭

77%
+5 −0
Deriving resistor values for a taper pad attenuator

A taper pad is a resistive attenuator that maintains impedances on both ports and provides a specific amount of gain-loss ($A_{12}$): - I have derived formulas for each resistor (that I know to ...

3 answers  ·  posted 12mo ago by Andy aka‭  ·  last activity 1mo ago by Lorenzo Donati‭

75%
+4 −0
Correct way to think about thermal noise?

I have just started learning about thermal noise in op-amps and while studying could not find if the noise given in op-amps data sheets is random sample to sample regardless of the time interval be...

1 answer  ·  posted 2mo ago by Joel‭  ·  last activity 2mo ago by Lorenzo Donati‭

75%
+4 −0
Why arc welding does not require high voltage to arc?

I've heard that arc welding is getting done with low voltage. I believe arcing requires high voltage. Then how is arc welding done with about 50 volts? I thought we need kilovolts for arcing. Why? ...

3 answers  ·  posted 9mo ago by mohammadsdtmnd‭  ·  last activity 6mo ago by TonyStewart‭

75%
+4 −0
What is the difference between rise/fall time and Turn-On/off Delay Time?

Hi guys so recently i was looking for a mosfet and a gate drivers and between a lot of their specification the rise/fall time and Turn-On/off Delay Time sometime it called propagation. My question...

2 answers  ·  posted 10mo ago by deleted user  ·  edited 2mo ago by Lorenzo Donati‭

75%
+4 −0
Is concentric twist a common practice?

I have seen multiple sources on the web discussing what they call concentric twist harnesses. It boils down to having a wiring harness built in layers, where each layer is twisted around the previo...

0 answers  ·  posted 3mo ago by Sclrx‭