How many times something happens per second, measured in Hz (Hertz).
4
votes
0answers
50 views
Distorted lm386 circuit output waveform
For one of my electrical engineering labs, we are required to build an lm386 circuit with a gain of 40, then measure its frequency response. I have successfully done the first part - I get a gain of ...
6
votes
1answer
59 views
How does a zero in transfer function affect the bandwidth of a system
Suppose we have a system with the closed-loop gain:
\$\displaystyle G(s) = \frac{\omega_n^2}{s^2 + 2\zeta\omega_n+\omega_n^2}\$
Which is the default two-pole system closed-loop gain. Let's also ...
2
votes
1answer
71 views
Simple logic circuit to filter out the even numbered pulse?
I need a logic circuit to have a function as shown in the figure:
An input signal applied to the input end, I want it to only output the odd numbered pulse and output 0 for the even numbered pulse. ...
0
votes
1answer
49 views
Is it the frequency that determines the current in a LC Tank Parallel Circuit?
Jump a head to the question if you aren't interested in the background of my project
Background of my project
I want to create objects of metal. So I need to be able to cast a metal. Aluminium seems ...
4
votes
6answers
121 views
What decides the range of FM band?
I read that the frequencies over which FM signals can be transmitted is limited between 88 MHz and 108 MHz. Why is it confined to a particular range and why specifically to this (88 MHz to 108 MHz) ...
1
vote
0answers
34 views
Power El wire from Mains
I have been looking at EL wire inverter, and most are battery powered.
I want to power it from mains power.
I was looking at having a transformer to step down from 220AC to 110AC.
This gives me 110AC ...
0
votes
4answers
64 views
How to find lower 3dB and upper 3dB from PSPICE frequency response
I have simulated the frequency response of an amplifier circuit. Frequency range is from 10 Hz to 2.5 MHz. It gave me a plot with a y-axis range going from -50 to 50. I assume these are dBs but I am ...
2
votes
3answers
75 views
Buck regulator frequency requirements (transient response)
Looking at the frequency choices for buck regulators, is there a defined "good" range for
a particular context? Looking at datasheets, manufacturers extoll the virtues of "better transient response". ...
0
votes
1answer
79 views
Frequency Selective Voltmeters
Does anyone here know of any cheap-ish handheld meters that are capable of measuring the voltage at specific audio frequencies?
I'm dealing with a few constant frequency signals on the same wire - ...
1
vote
2answers
127 views
Sawtooth/ramp waves with fixed amplitude from sine or square clock source?
I hope someone can help me out!
A bit of background info:
I have created a DDS based signal generator (Using PIC MCU to drive a AD9833 for DDS output). The generator is capable to produce sine, ...
6
votes
1answer
91 views
How susceptive is an inductor to frequency and current?
According to Coilcraft - Testing Inductors at Application Frequencies the inductance of a coil changes with frequency and current. Most datasheets don't give a frequency-inductance plot and ...
3
votes
2answers
202 views
What does it mean when they say 50MHz oscilloscope with 250MS/s sample rate?
I want to buy a digital oscilloscope to see how a WiFi module transfers signals and data. But I don't know which specification should I take into account?
Actually I don't know what the difference is ...
-2
votes
1answer
72 views
Changing Low Frequency to High Frequency [closed]
Is there any kind of circuit that could take 60Hz and completely change it to some higher frequency using ONLY inductors, capacitors, and resistors?
2
votes
1answer
56 views
STM32f2xx could not work with maximum frequency
I'm using default configuration (according to UM1061, RCC section) to configure an SMT32F215RG to work with 120MHZ CPU clock.
here is my configurations:
...
2
votes
1answer
134 views
What frequency and voltage should the electrical outlet have in order to be the least harmful to humans and still be useful to modern appliances?
Studying electronics a few years back I came across a graph like this one:
Showing that 50-60Hz current that is by far the most popular power coming from the electrical outlets in homes everywhere ...
0
votes
1answer
23 views
Measuring RF transmitted Power
I am running a software radio application. I need to measure the power of transmitted ofdm signal. The issue is that FCC has regulations of -50dBM/Hz. So I understand that if i need to send a signal ...
-1
votes
2answers
129 views
how to make frequency divider?
Can anybody show me how to make divider by 3 frequency using flip flop and logic gate ?
Does anyone here have any good suggestions ?
4
votes
2answers
198 views
Is there any way to differentiate the sound of blowing air from normal sound through phone microphone?
I have been working on an Android app that takes input from microphone when user blows into it. I am using FFT based sound analysis and converting the values in frequency by using a zero crossing ...
0
votes
3answers
85 views
Electromagnetic charging
I'm building a circuit that uses a really low voltage and current. I thought that instead of using a standard battery it would be nice if I could use a rechargeable battery and charge it with ...
5
votes
3answers
183 views
What is the unit for resonant frequency?
What is the unit for resonant frequency? where \$\omega_0 = \frac{1}{\sqrt{LC}}\$? Is it just \$HF^{-1}\$?
1
vote
1answer
113 views
Whats the principle of a PLL used as demodulator of a FM signal?
I didnt quite understand te following:
A basic PLL consists of the following parts:
phase detector
low pass filter
VCO
If you input a 1MHz sine the PLL will try to lock on it by controlling the ...
0
votes
2answers
69 views
How does using Flip Flops between transmission links increase the maximum clock speed?
I am learning about things such as propagation delay and Transmission delays. About how they limit the maximum Clock speed in a given system (where all the chips use the same clock line).
I can't ...
0
votes
0answers
91 views
Ask a way to pass high frequency PWM trough PC817（PC847）？How to realise this goal trough push-pull？
I am using PC847（datasheet ）to isolate a PWM control signal from CPLD. I will describe my design .When duty cycle changes from low to high, the forward current changes from low to high, so I have to ...
2
votes
1answer
43 views
mirror in frequency domain
Why is that in the frequency domain, I always see mirror images? What causes these mirror frequencies to appear? How do they pop in? Where do they come from?
Secondly, what is this concept of ...
4
votes
1answer
83 views
Least noisy pre-amplifier design
I am building a frequency generator circuit and need some advice. I am using the AD9833 DDS generator (programmed from a PIC16F876) to generate frequencies and I wish to be able to adjust the gain.
...
3
votes
1answer
170 views
At what frequency will the reactance of a 1μF capacitor equal to the resistance of a 2kΩ resistor?
Here is my work:
\$ R = 2000 \Omega\$
\$ X_L = 2 \pi f L = 2 \pi (1 \mu F) f = 6.28\mu F(f)\$
\$f = \dfrac{2000 \Omega}{6.28 \mu F} = 318.471MHz \$
Does this look right to everyone?
0
votes
0answers
85 views
lm555 circuit doesn't work
Why doesn't this simple circuit work?
\$R_1 = 15k\Omega\$
\$R_2= 15k\Omega\$
\$C_1= 1000\mu F ; 6.3V\$
\$v= 9V\$
It should have a cycle time of 30 seconds.
I placed a volt meter on a LED that was ...
1
vote
1answer
60 views
Difference between Max Interface Clock and Max Timer Clock?
I am trying to use a timer from STM32F4 with ARM Cortex-M4 chip. I need to get the maximum frequency out of that timer for my ...
3
votes
2answers
119 views
Making my own PCB connectors, but having trouble with high frequency signals
I'm making my own PCB connectors using the "multicomp" range of crimp connectors available from farnell (ex. http://uk.farnell.com/multicomp/2226a-04/crimp-housing-1-row-4-way/dp/1593508 with ...
1
vote
1answer
221 views
Reading the frequency of an AC signal using an arduino
Basically I have a motor with a magnet spinning on the end. I have a sensor that produces an AC signal when the spinning magnet is placed next to it. It produces a voltage of ±300mV. I want to measure ...
2
votes
1answer
182 views
Calculation of cutoff frequency in larger circuit
I'm having some difficulties choosing appropriate resistors and capacitors to get specific cutoff frequencies. I guess it's because I'm just considering the single pole components rather then the ...
2
votes
1answer
64 views
Frequency Scaling and current draw
I am trying to power a RPi of 4 AA's, and my mobile power device can only output limited current (500mA), but I can underpower my RPi by frequency scaling. Is frequency scaling and current draw a ...
-2
votes
1answer
302 views
At very high frequency (700 kHz), an AC circuit has a voltage reading 10 times the EMF, why is this?
I've set up an experiment in which I vary the frequency of an electric signal using a waveform generator. The experiment is testing a transformer, but I've encountered a problem on the primary circuit ...
2
votes
1answer
159 views
Power consumption and frequency
I am making a small, mobile device with the Raspberry Pi that depends on batteries, so power consumption is an issue. I have scaled the "arm_freq_min" (unsure if clock or instruction cycle frequency) ...
-3
votes
2answers
77 views
Would we have communication theory and systems without trignometric ratio? [closed]
Trigonometric identities happen to be invented for triangles: sin, cosine and through them tangent.
Later at school I learnt that they are periodic and have wave appearance. Than in University I came ...
0
votes
1answer
92 views
Frequency Response Help
A discrete-time linear and time-invariant (LTI) system is given by the following
input-output relationship: y[n] = 2x[n] − x[n − 1], where x[n] is the input and y[n] is the
output.
(a) What is the ...
0
votes
2answers
81 views
Does nodal analysis work with alternating currents if every step is treated like DC?
I have a question that is difficult for me to describe.
I want to know if I will get accurate readings of an AC circuit by nodal analysis if I treat each significant voltage change as a DC circuit.
...
1
vote
1answer
158 views
Why cable TV frequency range ends at 1 GHz?
Currently frequencies 50-1000 MHz are allocated for TV and data transfers. I understand why there are limitations for aerial or satellite transmissions, but why are they retained for cable ...
0
votes
2answers
598 views
15V 3A dc motor PWM frequency setting
What is a suitable frequency for 15V/3A DC motor? Is there any effect on the motor when the frequency is changing? I am confused with this until now and the Internet shows a lot of theory that ...
4
votes
2answers
505 views
Frequency multiply a digital signal using pure digital ciruitry (i.e. without PLL)?
Is it possible to multiply the frequency of a digital signal using digital components alone, and at the same time, preserve the duty cycle?
I could finally come across the circuit below: it doubles ...
2
votes
1answer
588 views
How config STM32 with two different Clock speeds
I'm using STM32F103RE for implementing a time-consuming operation. This device is connected to PC via USB port. I'm not expert in configuring these MCU, but seems when it configures to communicate via ...
19
votes
6answers
848 views
How precise is the frequency of the AC electricity network?
If I make a digital clock which first detects the AC frequency roughly (whether it is 50, 60, 100Hz, etc), then uses it as its clock pulse source, how precise would it be? Would it work world wide ...
1
vote
3answers
190 views
Wobble Bass LFO circuit with Op Amps
I am trying to build a LFO circuit that produces a wobble bass effect.
My overall plan is using an Op Amp to create the LFO and another Op Amp to create the low pass filter. How should I connect ...
-1
votes
1answer
92 views
frequency generator and power supplies
I am going to do mini-project (school level), for which I need a power supply (in the range of +5v dc supply) from ac main (230v, 50Hz) and frequency generator (for a range up to some kHz, sine wave).
...
0
votes
2answers
237 views
calculating FSM's maximum clock frequency
Let's assume we have the Truth Table for our Finite state machine.
How can we determine the maximum clock frequency for the system, under the assumptions that the wire delay is 0.3 ns , flip-flop ...
4
votes
2answers
197 views
Why are low frequency channels (10kHz - 200kHz) especially susceptible to interference?
I am working on a system which should communicate with a ~100kHz signal, and read that low frequency channels, e.g 10kHz to 200kHz, are especially susceptible to interference.
Why is that? Are they ...
4
votes
3answers
236 views
How is microphone's frequency response determined
It seems this is the chicken and egg problem. To be able to determine the frequency response of a microphone one needs a speaker that has a known response. To be able to know the response of a speaker ...
5
votes
3answers
411 views
Can LEDs or optocouplers be used without a resistor if PWM is used?
LEDs are often connected through a resistor and the purpose of this seems to be to lower the voltage across the LED to around 1.8V. Can PWM be used to lower the voltage instead of a resistor? If so, ...
3
votes
2answers
287 views
Reading frequency of an audio signal from Android device
I am doing a project that reads frequency of audio signals generated from Android device through the headset jack. The audio jack is connected to Atmega microcontroller as shown in the figure.!
I am ...
0
votes
2answers
212 views
How to create a square wave signal with 120MHz
What is a cheap way to generate a square wave with a frequency of 120MHz. I've been thinking of the following solutions:
* Use a Raspberry Pi, then use a timer or something from that board
* Use an ...
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