Questions tagged [frequency]

How many times something happens per second, measured in Hz (Hertz).

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1answer
76 views

Hacking ATM with its aux port [closed]

(I opened a topic about it a few minutes ago but I thought it would be better if I ask my question more properly.) I wonder if is it possible to hacking an ATM (through it's aux port) with connecting ...
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25 views

Parasitic capacitance of a chip

I know that the parasitic capacitance of a chip is pronounced Cdyn. If I apply on some scenario one the chip which will toggle the all of its transistors with two different voltages, but the frequency ...
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39 views

The criterias to select peak detector capacitance and resistance [duplicate]

edit: diode is replaced with 1n4148 While designing such a peak detector, what should be the approach of choosing C and R values? Which specs of the detector will be based on them? I assume their ...
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1answer
39 views

Question: AC Voltage and Current variables

So I know how alternating current is produced, but I'm curious to what determines the voltage and amount of current moving within the wire. Does the frequency of the alternations give more voltage/...
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3answers
158 views

Frequency response of this circuit

Im not sure how to find the frequency response (\$H(jw)=V_o/Vin\$) of this circuit Can anybody help please?
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2answers
95 views

How does a microcontroller provide a frequency higher than its crystal frequency? [duplicate]

I have a microcontroller which is connected to an 8MHz crystal. I have a schematic which has a QSPI flash IC connected to it whose clock is provide by the micro and happens to be 48MHz. I want to ...
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1answer
63 views

Frequency Circuit

I have seen this circuit on internet. I would like to understand what its purpose is. It seems to be related to something which is call "jitter." I have done some research about "jitter" and I think ...
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3answers
87 views

Why is the impedance zero at cutoff frequencies in a series RLC resonance circuit?

I see that, in many derivations in the frequency analysis of series RLC circuits, \$X_L - X_c = R\$ or \$Xc - X_L = R\$ is considered at lower and higher cutoff frequencies. So does that mean that the ...
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43 views

“Trace Max Hold” function in spectrum analyzer

I have seen my professor doing a measurement with the spectrum analyzer in which he wanted to evaluate the frequency response of a bandpass filter. He used a signal generator in sweep mode from 1MHz ...
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1answer
59 views

Low Frequency EMI

I was wondering if low frequency EMI can occur with PWM or other sub MHz signals. I am aware that harmonics of these signals can generate EMI but I was wondering if the fundamental frequency can ...
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1answer
65 views

Ambiguity in the Definition of Resonance Frequency

we know that in a series LC circuit the resonance frequency is defined as that frequency in which the total impedance offered by the circuit is zero. We also know that in a parallel LC circuit the ...
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5answers
136 views

Sampling theorem clarifications

whenever the sampling theorem was explained to me, a situation of this kind was proposed to me. If we look at the previous image we will see that the condition to avoid spectral aliasing is that we ...
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1answer
35 views

Tuning Resonant Cavities

I have seen that some resonant cavities are equipped with some external screws, called tuners, which can be used to vary the resonance frequency. Can you explain me the physical reason with which to ...
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3answers
91 views

How to add value of 5e^(-25/2t)u(t) to a voltage source in LTSpice?

I want add the following value 5e^(-25/2t)u(t) as a Vin to my circuit in LTSpice. However I don't know how to do this - can someone help?
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1answer
257 views

Clock frequency divider circuit (divide by 2) using D flip flop

I was trying to implement frequency divider by 2 using D flip flop with the logic connection of ~Q to D input. I provide 2x clock frequency of 50% Duty cycle in the hardware where D flip flop is made ...
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1answer
31 views

change in ac reading relative to the frequency

I'm working on a school project, just measuring the Vrms of two different waveforms at different frequencies. The function generators output is connected directly into an oscilloscope therefore the ...
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64 views

In an automotive ECU application for STM32, what ADC modes should I use?

I am writing an application for the STM32f407-Discovery board that will use the ADCs present on it. I want to have access to all 17 of the input channels, and I will be using the HAL library to write ...
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1answer
92 views

Finding frequency of a series of pulses (3 - 60 Hz) without using a microcontroller or frequency-to-voltage converter

I came across an interesting yet challenging problem of finding the frequency of a series of pulses. The pulses can have a frequency anywhere from 1 to more than 100 Hz. The goal is to detect if the ...
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2answers
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Why do most flyback converters / LED drivers operate under 100 kHz?

Most of the LED drivers and flyback converters I have come across operate in the 60-100 kHz range. Is there any particular reason behind this - example - ferrite cores not being able to handle higher ...
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3answers
243 views

How does Laplace transform include the transient response?

When we provide a sinsusoidal input, the evaluation of the solution of the differential equation head-on becomes horrendous. So we give an imaginary, complex exponential input and solve the ...
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0answers
30 views

What could potentially affect some specific LoRa frequencies among others and how to mitigate it?

I have started a small LoRaWAN network. I already have setup: 1x LoRaWAN gateway (LAIRD RG186, using EU863-870); 4x T/RH Nodes (Dragino LHT65, same standard); LoRa ...
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53 views

Voltage Measurement through Spectrum Analyzer

I have done some measurements with a Spectrum Analyzer of a square wave of 100kHz and amplitude equal to 1V. The resulting power spectral density is here shown: The highest peaks represent the odd ...
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1answer
70 views

How does relative permittivity decrease with frequency while capacitance doesn't?

As I understand, capacitance is $$\frac{\varepsilon A}{d}$$ where ε is the absolute permittivity. If the capacitor's dimensions are kept constant, then a change in ε with frequency should mean a ...
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2answers
88 views

Resistor annotated with a frequency

The LT3757 datasheet includes the following schematic: The resistor in the bottom left corner is annotated with a frequency (100kHz). What is the significance of that annotation?
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6answers
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Where do overtones in a 555 generated square wave come from?

I have built a 555 oscillator and connected it to a speaker. Using an oscilloscope I adjusted the 555 to generate a 2.5kHz square wave. I then held a microphone up to the speaker and fed the input ...
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22 views

Sequential NAND Based Phase-Frequency Detector output

I'm trying to understand the output of my phase detector only for a pulse that goes from zero to one. here is my schematic: (ref is Clk_ref, and Div is Clk_out, both come from an outside circuit) ...
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1answer
52 views

what does phase really mean?

I'm new to EE, and I am reading a text book which says: Phase describes the position of the waveform relative to time 0. The a quiz asks What is the phase shift for a sine wave with the maximum ...
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30 views

comparing between different phase detectors

I implemented two architectures of phase-frequency detectors and I'm interested to compare between them. (I'm open for extra architectures that might solve problems that I'm not discussing here) I'...
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2answers
91 views

Phase detection with non-ideal PFD

I'm trying to simulate for Phase Frequency Detector with the following implementation: and inside NAND_PFD: NOTE: the triangles on the right are inverters and not amplifiers. I'm currently ...
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3answers
88 views

approximation of a digital signal using the harmonic

I'm new to EE, still struggling in understanding some basic concepts. I'm reading a book which says about approximation: To make the shape of the analog signal look more like that of a digital signal,...
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3answers
53 views

Why phase is the position of the waveform relative to time 0

I was reading a book which says: Phase describes the position of the waveform relative to time 0. It indicates the status of the first cycle. and below is a picture I am a little bit ...
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1answer
51 views

why nonperiodic signals still has the concept of frequency?

I'm new to EE from CS background, just a question on nonperiodic signals. I don't understand why nonperiodic signals still has the concept of frequency/frequency domain? The definition is : Period ...
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1answer
47 views

Accurate signal reconstruction

While reading through this page I came across following info: "For accurate reconstruction using sin (x)/x interpolation, your oscilloscope should have a sample rate at least 2.5 times the highest ...
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2answers
69 views

In general, construction wise, what makes a speaker more or less sensitive to mid tones?

I bought a second hand vintage boombox and the left (full-range/'woofer') speaker has gone so I replaced both speakers with some Sony ones. The Sony ones are taken from of cabinets lying around (the ...
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28 views

What is an equation that will show RF wave characteristics?

I want to show a RF wave on a spherical grid coordinate system. How can I show the RF wave when t = time and y = magnitude? I also want to show curvilinear coordinate transitions of the RF wave ...
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79 views

Frequency compensation of a two-stages class AB amplifier

The author of the book on which I'm studying explains in depth the following "standard" two-stages op-amp: In order to deal with frequency compensation, he models each stage with a transconductance ...
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2answers
104 views

Is 1 Hz equal to 1 rotation of a motor shaft?

I'm rather new to the world of electronics but I have been trying to find the frequency of a DC motor. I've found that 1 hz is equal to 1 revolution per second, but does that refer to shaft rotation ...
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3answers
608 views

Why would an AC motor heavily shake when driven with certain frequencies?

I have an AC motor from an old TCL 160 Boxford NC Lathe, it has three wires named U V and W. I thought that incorparating the original driver to a modern control interface card would be difficult or ...
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5answers
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Laptop failure due to constant fluctuation of AC frequency and voltage [closed]

I spend most of time on a boat (not on holiday :/ ) where a huge generator provides electricity. The potential problem is that the output is very dependent of the "mood" of the engine. Sometimes the ...
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3answers
172 views

Inconsistency in Values of Laplace Transformed Current when Changing Units

I was trying to convert the units of the following current in Time Domain and Complex Frequency domain (s-domain): $$ i(t)=20\cdot e^{-t}H(t)\,\,\,\,\,\text{[mA,ms]} $$ Where \$\text{[mA, ms]}\$ ...
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2answers
98 views

what is this type pulses called?

I was wondering what is this type of pulses is call. Is it a sin wave? I know its the result of sinusoidal pulse modulation. is it considerd a quasi-sin wave? I would like to know the name to ...
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50 views

Power spectral density on the output of frequency modulator?

Is there a formula with which we would be able to calculate the power spectral density on the output of a frequency modulator? The information we know is that we have a receiver working in 180MHz ...
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1answer
83 views

Is it normal to be able to hear a high pitch buzz from devices that are charging?

I have noticed that in ungrounded outlets I am able to hear an almost silent high pitch sound if I plug in earphones into the device being charged. I think this is the 50 Hz electrical signal that I'...
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2answers
69 views

Frequency Sensitive Switch

A legacy product we are making uses this obsolete Frequency Sensitive Switch, Consumer Micro FX-301L. The switch is setup such that it switches on (-12V) at 2000Hz +-100Hz and switches off at 250Hz. ...
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1answer
99 views

Can I generate frequencies faster than 32 MHz with ATTINY85?

I believe I can use the 64 MHz PLL clock with PWM to toggle every cycle and thereby generate a 32 MHz square wave output on an IO pin, right? Is there a trick to generate an even higher frequency (...
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1answer
185 views

Arduino- Duty Cycle Changing When Frequency Is Increasing

I’m currently trying to increase the frequency from a pin from an Arduino using PWM. I’m using the Timer1 library as it has functions to output signals. I connected a push button to my Arduino and ...
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1answer
50 views

Complex Amplitudes and Exp'l Increase/Decrease

The following are quotes from a textbook, If S(t) is represented as a rotating phasor, the angular frequency of the phasor can be thought of as velocity at the end of the phasor. In particular ...
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4answers
3k views

Can sampling rate be a floating point number?

Suppose we have a sampling frequency for a signal of 15.5 samples/sec and we take samples for a period of 7 seconds. This means total samples are 108.5, does this make any sense? Shouldn't the ...
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1answer
84 views

If I look at a signal in its frequency domain, are there some guidelines by which I can tell how that signal looks in the time domain?

I was studying the Laplace transform and the Fourier transform, and I can't figure out if there is some intuitive way of finding out how a signal looks in the time domain if we know its frequency ...
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166 views

STM32 simultaneous PWM output with variable frequency and duty cycle

I've been designing a capacitor discharge welding machine for a while, So the working principle is when the button has been pushed, 3 output will initiate simultaneously which 2 of them is variable ...

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