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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.

66%
+2 −0
Possible stray current corrosion in reinforced concrete

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

1 answer  ·  posted 10h ago by Willem ‭  ·  edited 5h ago by Olin Lathrop‭

40%
+0 −1
How to calculate the voltage of a coil?

Hi guys, I need to calculate the voltage that will center the magnetic field of a coil. The coil gonna be used in an induction heater thank you. Edit: I edited the paragraph because it was misu...

1 answer  ·  posted 1d ago by Freewell‭  ·  edited 2h ago by Freewell‭

66%
+4 −1
Minimizing Common Mode Radiation - Separating Grounds

There are various different methods to keep common mode currents off the cables, one of them being discussed on the site here and with Olin's decoupling caps post on StackExchange. Slight digressio...

1 answer  ·  posted 10d ago by 2kind‭  ·  last activity 4d ago by TonyStewart‭

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+2 −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 13d ago by Freewell‭  ·  last activity 4d ago by TonyStewart‭

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+3 −0
Is it possible to calculate the rise/fall time of an operational amplifier ?

Hi guys so i am planning to use LM318 operational amplifier to generate a pwm signal and i need to know how to calculate the rise/fall time thank you. LM318/LM218/LM118 datasheet Edit: -The slew...

1 answer  ·  posted 15d ago by Freewell‭  ·  last activity 13d ago by Olin Lathrop‭

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Need help to replace 555

Hi guys, Can anyone help me please replace the NE555 IC in this circuit by MIC1555. I need to modify also the Voltage to 18v thank you. MIC1555 datasheet NE555 datasheet Edit: The circuit a...

0 answers  ·  posted 15d ago by Freewell‭  ·  edited 12d ago by Freewell‭

555
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+4 −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 21d ago by Lundin‭  ·  last activity 21d ago by Lundin‭

25%
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BJT common emitter amplifier equivalent circuit (π hybrid model) [closed]

Im studying the equivalent model of a BJT common emitter amplifier at high frequencies.At university we tought that the BJT at high frequencies looks something like this: However when designing ...

0 answers  ·  posted 27d ago by MissMulan‭  ·  closed 27d ago by Olin Lathrop‭

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Thermal stability coefficient

The thermal stability coefficient is defined to be: $S = \frac{dI_{C}}{dI_{CBO}}$ where $I_{CBO}$ is the reverse current of the BJT when voltage isnt applied to the base of the BJT. In case of a ...

1 answer  ·  posted 1mo ago by MissMulan‭  ·  last activity 1mo ago by TonyStewart‭

71%
+3 −0
Energy harvesting from non-invasive current sense transformer

I have a non-invasive current sense transformer (SCT-013-030) which according to its datasheet it is voltage output type. I want to harvest energy and supply a wireless sensor that consumes 5-6 uA...

1 answer  ·  posted 1mo ago by DeadMouse‭  ·  last activity 1mo ago by Andy aka‭

66%
+2 −0
Ceramic filter vs ceramic resonator

I have a design of a power line communication using the following IC. https://www.yamar.com/datasheet/DS-SIG60.pdf My design is the same as the example circuit in the datasheet of the chip. Th...

2 answers  ·  posted 2mo ago by DeadMouse‭  ·  last activity 2mo ago by TonyStewart‭

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+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 2mo ago by Andy aka‭  ·  edited 2mo ago by Andy aka‭

75%
+4 −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 ...

3 answers  ·  posted 2mo ago by Nick Alexeev‭  ·  last activity 1mo ago by Olin Lathrop‭

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+4 −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 ...

2 answers  ·  posted 2mo ago by Andy aka‭  ·  last activity 2mo ago by a concerned citizen‭

57%
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pH Electrode Buffer - Offset when solution grounded

Problem pH electrode buffer offset appears when solution is grounded. Detail I have a pH electrode in some conductive solution (~1000uS). The output (measurement electrode) is buffered by an el...

2 answers  ·  posted 3mo ago by rherma‭  ·  last activity 2mo ago by TonyStewart‭

25%
+0 −4
Designing a circuit to verify thevenin theorem with induction motor as load [closed]

Design a suitable experiment and an AC circuit to verify Thevenin's theorem when the load is a single-phase induction motor with a capacitive start and two supplies feed the load. Ratings of load:...

0 answers  ·  posted 3mo ago by dkumar94600‭  ·  closed 3mo ago by Olin Lathrop‭

81%
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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 3mo ago by kadamrohan16‭  ·  last activity 3mo ago by Andy aka‭

62%
+3 −1
Power amplifier for remote controller

I'm designing remote controller based on NRF24L01 and STM32. I want to use SMA antenna. My question is regarding power amplifier (PA). When is it necessary to use one? The range I'm aiming for is 2...

3 answers  ·  posted 3mo ago by Stefan‭  ·  last activity 3mo ago by Andy aka‭

75%
+4 −0
Can confusing the plugs for earphones and microphones do any damage?

The plugs for microphones and for earphones are the same, however their functionality obviously is quite different. Now because of the same plugs it is easy to insert one of them in the wrong socke...

2 answers  ·  posted 3mo ago by celtschk‭  ·  last activity 3mo ago by TonyStewart‭

66%
+2 −0
Circuit which create ac sine wave from dc pulsed signal

A full wave rectifier converts a sine wave to DC pulsed signal of double frequency. Is there a circuit which does the reverse process?

2 answers  ·  posted 4mo ago by MissMulan‭  ·  last activity 4mo ago by TonyStewart‭

71%
+3 −0
What are the key programming skills for an embedded systems engineer?

I am looking to improve my knowledge of embedded systems programming, specifically regarding microcontrollers and embedded Linux systems. A lot of the information that can be found regarding C/C++...

1 answer  ·  posted 4mo ago by Mu3‭  ·  last activity 4mo ago by Olin Lathrop‭

20%
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Need help design a digital circuit which divides two binary numbers [closed]

Before the circuit here are the digital blocks which have been already designed and exist as part of the division block 1 bit subtractor: 2 bit subtractor(in the digital block diagram of the di...

0 answers  ·  posted 4mo ago by MissMulan‭  ·  closed 4mo ago by Olin Lathrop‭

71%
+3 −0
Battery protection circuit

I am using two 18650 cells in series to power a RC car. Is the voltage goes below 6.2 V, the battery should be disconnected to prevent over discharging the battery. At the same time I want to imple...

2 answers  ·  posted 4mo ago by Stefan‭  ·  edited 4mo ago by Stefan‭

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+3 −0
Pick & place file generated by Altium does not match the actual component rotations/positions

I am generating files for manufacturing my design in Altium 22 and ordering through Eurocircuits. What I noticed during the ordering process is that the rotation of many components (and sometimes ...

1 answer  ·  posted 4mo ago by Mu3‭  ·  last activity 4mo ago by DSI‭

33%
+0 −2
Op Amp Hartley oscillator

Im designing a Hartley oscillator this time with a opamp providing the open-loop gain.I have tried drawing the small-signal analysis of my circuit to use KVL and KCL to find the conditions of opera...

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

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+1 −0
Results of analysis of Hartley oscillator dont make sense

I want to find the conditions of oscillation of the following Hartley oscillator.I have attached a load (ZL) to my Hartley oscillator I have written KCL for nodes A,B: For node A: $$\frac{V_{A...

3 answers  ·  posted 5mo ago by MissMulan‭  ·  last activity 4mo ago by TonyStewart‭

71%
+3 −0
Altium. Reusing schematic symbols for pin-compatible parts.

I want to create a schematic symbol and reuse it for multiple ICs which have identical pinouts. For example, OpaMPS, or the venerable SN74LS00, SN74HC00, SN74HCT00. How can I do this in an Altium...

1 answer  ·  posted 5mo ago by Nick Alexeev‭  ·  last activity 4mo ago by Mu3‭

50%
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Modelling tunnel diode relaxation oscillator

I have been trying to model this oscillator I was wondering if we can somehow predict the frequency of the oscillations.For small currents inside a diode from the Shockley diode equation $$ e^{x...

1 answer  ·  posted 5mo ago by MissMulan‭  ·  last activity 5mo ago by a concerned citizen‭

25%
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DC-DC converter using Hartley oscillator and transformer [closed]

Instead of using a buck or a boost converter can we use for DC-DC conversion the circuit Im going to describe in the next lines? First we begin with a Hartley oscillator whose output is fed into ...

0 answers  ·  posted 5mo ago by MissMulan‭  ·  edited 5mo ago by MissMulan‭

33%
+0 −2
Small signal analysis of BJT in saturation region

The small signal analysis of a BJT when the BJT is in amplification mode: is easy.However what happens when the BJT is in saturation mode? Can we replace the dependent current source with a r...

1 answer  ·  posted 5mo ago by MissMulan‭  ·  edited 5mo ago by MissMulan‭

28%
+0 −3
Design high -pass filter with 2 points of the bode plot

Im designing a high-pass filter which has a gain of -8dB at half of the roll-off frequency and I am stuck ,I dont know how to continue the design. In the bode plot of that filter we have 2 points:...

3 answers  ·  posted 5mo ago by MissMulan‭  ·  last activity 3mo ago by LvW‭

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Band pass filter given cutoff frequency and bandwidth

I have decided to try design a band-pass filter with a cut-off frequency of 10kHz and bandwidth of 2 Hz. $$ \frac{1}{\sqrt{LC}} = 10001 \rightarrow LC = 1/100020001 sec^{2}$$ $$ \frac{R}{L} = 2...

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

50%
+0 −0
Finding voltage gain of Hartley oscillator

I am trying to find the AC analysis of a BJT Hartley oscillator but I cannot continue. How do I find the voltage gain? When no feedback is there, we just find the output resistance and the current...

1 answer  ·  posted 5mo ago by MissMulan‭  ·  edited 5mo ago by MissMulan‭

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Complex frequency of a pole

If we have the transfer function of a LC high pass filter: $H(s) = \frac{sL}{sL+\frac{1}{sC}}$ If we want to find the pole of that filter in the end we get: $s = \frac{j}{\sqrt{LC}}$ and for a ...

3 answers  ·  posted 5mo ago by MissMulan‭  ·  last activity 5mo ago by Andy aka‭

33%
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Effect of adding stages to a filter

Suppose we have a RC low pass filter of 1st order. If we add multiple stages every time we add a RC stage identical to our original does the slope of the curve in the bode plot db/Hz becomes wild...

2 answers  ·  posted 5mo ago by MissMulan‭  ·  last activity 2mo ago by a concerned citizen‭

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 5mo ago by MissMulan‭  ·  reopened 5mo ago by Olin Lathrop‭

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How to design a low-pass filter when certain conditions must be met

I am designing a low-pass filter with cut-off frequency = 100Hz and after the cutoff frequency from -3dB to -10dB the average decrease in db/Hz = -0.1 db/Hz.I know how to design a low-pass filter ...

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

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 5mo ago by Elleanor Lopez‭  ·  last activity 5mo ago by Elleanor Lopez‭

71%
+3 −0
Limiting current to DC brushed motor

This question is related to my previous question. I want to drive a brushed DC motor using H-bridge. To power the motor two 18650 cells will be used in series. The issue is that I want to limit th...

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

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H-Bridge components and calculations

My goal is to make an RC car, and I have a couple of questions regarding driving the brushed DC motor. Schematic for half of my H-bridge looks like this for now (it will be identical on the other s...

1 answer  ·  posted 5mo ago by Stefan‭  ·  last activity 5mo ago by Stefan‭

66%
+4 −1
Mysterious little cases hanging on street wirings

I have been observing these little cases hanging to the wires from a long time and almost everywhere but unable to find out what it is.I am not sure whether they are related to any electric...

3 answers  ·  posted 6mo ago by aditya98‭  ·  last activity 5mo ago by Jasen‭

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What effect will extreme temperatures have on impedance in 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...

1 answer  ·  posted 6mo ago by Lundin‭  ·  last activity 6mo ago by Olin Lathrop‭

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Find Q point in common base BJT configuration

Suppose we have this graph: How can we find the operating point (Q)?In common emitter collector we just draw a line from the vertical axis (Ic) at the point (0,VCC/RC) to the horizontal axis a...

1 answer  ·  posted 6mo ago by MissMulan‭  ·  last activity 5mo ago by Circuit fantasist‭

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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 6mo ago by Elleanor Lopez‭  ·  last activity 6mo ago by Andy aka‭

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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 6mo ago by MissMulan‭  ·  last activity 6mo ago by LvW‭

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Thévenins Theorem for Transistor Circuit

I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1 and R1, R2 into Vth and Rth as shown in the image. Vt...

2 answers  ·  posted 7mo ago by kadamrohan16‭  ·  last activity 7mo ago by Olin Lathrop‭

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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 7mo ago by NMOS lover‭  ·  last activity 7mo ago by Andy aka‭

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How do PLCs normally measure 4-20mA current loops?

I'm looking for input from anyone with insight in the PLC world. How do PLCs usually measure 4-20mA current loops? I would assume it's one of these two alternatives: Through an external "shunt"...

3 answers  ·  posted 7mo ago by Lundin‭  ·  last activity 2mo ago by KalleMP‭

66%
+2 −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...

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

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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 8mo ago by 2kind‭  ·  last activity 8mo ago by TonyStewart‭