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Questions tagged [frequency]

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

27
votes
6answers
23k views

How to convert AC to DC

I am designing a circuit that needs to output 5VDC @ 1A. I'm trying to use a wall transformer to step the voltage down to 12VAC. The next step is the diode bridge and ripple capacitor. The ripple ...
17
votes
4answers
16k views

How critical are UART frequencies?

I'm going to be using an 8 MHz crystal to run my microcontroller at 16 MIPS (PLL 4x, 2 cycle instructions.) However, 8 MHz doesn't divide into any UART frequencies AFAIK... so how critical are these ...
37
votes
8answers
9k views

Why do utility companies supply at a frequency of either 50/60 Hz?

It just struck me that Utility Companies world-wide supply domestic users at either 50/60Hz. It could have been selected to be 10 Hz, or 100 Hz ... whatever Was 50/60 chosen at random? Is there some ...
29
votes
6answers
14k 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 ...
3
votes
4answers
3k views

Basic Frequency Control Circuit

How does R4 prevent the output voltage drifting towards one of the supply rails to the op amp? I understand that R4 has to have a high resistance but I do not know why? Here is the schematic which is ...
1
vote
2answers
2k 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 ...
2
votes
5answers
30k views

Changing the frequency of an AC supply

I am using an AC Power supply, and the frequency of the wall plugs is around 50hz. Is there a way to increase this frequency keeping everything the same?
1
vote
3answers
6k views

Frequency Detection Circuit Design

I want to create a circuit that can detect audio frequencies and flash RGB LEDs different colors depending on the detected frequency. The frequency range will be from 20 Hz to 12 kHz, after looking at ...
3
votes
3answers
737 views

Reading frequencies without filters

Is it possible to read a set of frequencies with a PIC in such a way that for each frequency a different function is called? The idea was to send multiple frequencies at different times (no ...
66
votes
5answers
12k views

Serbia, Kosovo power grid row delays European clocks. Why?

According to this article (and a lot more published today on the same topic), Kosovo electricity net production balance has decreased during the last weeks. This has led to a small deviation of the ...
12
votes
2answers
2k views

Frequency ranges that causes a hazard to humans

I hope many people might feel little awkward to see this question. But I feel this is important. Because in my place where I am living I can get a radio (Audio Receiver) very cheaply. I don't know ...
2
votes
3answers
23k views

Resonant Frequency from Bode plot

If we have a transfer function that shows no peaking in the magnitude bode plot (Starting from a flatline and then rolling off). Does this mean that there is no resonant frequency? Or do we consider ...
10
votes
8answers
14k views

Maximum sample rate of Arduino Duemilanove?

G'day all! I have an Arduino Duemilanove hanging around spare at the moment and thought I might try a few audio interfacing projects. I'm just wondering what sort of sampling frequency I can achieve ...
9
votes
2answers
440 views

mains frequency accuracy worldwide

I like to build a device that needs long term time stability. In germany, one of the best simple clocks use the mains power frequency to obtain a time measure. While the frequency is allowed to change ...
6
votes
1answer
2k views

What does 100Ohm @ 100MHz exactly mean in ferrite beads?

I am trying to understand the parameters of ferrite beads and having trouble in understanding the impedance vs frequency parameter. What does 100Ohm at 100MHz exactly mean? Does it mean that the ...
1
vote
3answers
13k views

What is the equation for the 555 timer control voltage?

I was just wondering what the equation is to find the 555's output frequency is, when a control voltage is applied to pin 5. That would be very useful for me to know! [Edit By OP] So based on what ...
5
votes
3answers
10k views

Why is Cat5/Cat5e Ethernet cable rated 100MHz?

As the questions says, is there any specific reason why Ethernet cable is rated 100MHz? For a 100Mbps Ethernet the data rate is 100Mbps, and the baud rate is 125Mbaud, because of the specific line ...
0
votes
3answers
197 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 ...
0
votes
1answer
310 views

Finding the cut-off frequency

Find the cut-off frequency of this filter: My attempt: $$\text{H}\space_{\left(\omega\right)}=\frac{\text{R}_1+j\omega\text{L}}{\text{R}_1+\text{R}_2+j\omega\text{L}}=\frac{\text{R}_1+j\omega\text{L}...
4
votes
2answers
1k views

Obtaining Poles and Zeros from frequency response

What is the process of obtaining the poles and zeros from frequency response plot or data. Any reference or Matlab code will be great help
4
votes
3answers
3k views

Why is an op amp's bandwidth higher at lower gains?

If I build a resistor network where the op amp has a lower gain, it is able to maintain its gain for a larger bandwidth. Why?
2
votes
3answers
762 views

looking for a sensor that activates when hit by a certain frequency burst

I have a question that may seem silly, but I am only new at this type of thing:  Is there a sensor that I could connect to an LED (via an integrated circuit of some description, I assume) that ...
-1
votes
1answer
54 views

Can't understand concept, range of the pulse (waveform)

I am working on the lab which is allowed to ask other people for hints. In the image, program called "Audacity" is used to capture that waveform. Question 1 In the image it says, "The peak-to-...
-2
votes
2answers
208 views

Can a smartphone send directly a message to another smartphone 20 miles away? [duplicate]

According to this website, a typical cellphone has enough power to reach a cell tower up to 45 miles away So, can a smartphone send directly a message to another smartphone 20 miles away?
12
votes
1answer
4k views

Characterization of bypass capacitors

I was reading through a few post including Decoupling caps as well as this app note Xilinx Power Distribution Network. I have a question regarding capacitor values within a power distribution system. ...
29
votes
5answers
13k views

Why does a faster clock require more power?

If you overclock a microcontroller, it gets hot. If you overclock a microcontroller, it needs more voltage. In some abstract way it makes sense: it is doing more computation, so it needs more energy ...
23
votes
3answers
4k views

Negative frequencies: what is that?

I know that when the frequency is 0, the voltage will be pure DC. But in DSP and Digital Communication, I have seen mentioning of negative frequencies which I dont quite understand. For example, like \...
15
votes
5answers
2k views

How do you visualize negative Frequency in Time domain ?

In the field of Digital signal processing I have seen people using words Complex signals and Negative frequencies. For eg. in FFT Spectrum. Does it really have significant meaning in the time domain ...
15
votes
3answers
4k views

How can over 24 GHz communication be possible?

I read the article Google wants the US' wireless spectrum for balloon-based Internet. It says to use over 24 GHz frequency spectrum for communication. Is it ever possible to generate that high ...
13
votes
4answers
39k views

Is frequency for dc zero Hz?

We know the frequency of a direct current is zero. The reason is that there is no repetitive pattern. But I was stumbled when I noticed, why can't that straight line be cut into smaller pieces, and ...
10
votes
4answers
31k views

How exactly are radio waves produced from a current in a circuit itself?

I am 17, and I am new to electronics, and I've learned everything online and expect to continue to do so with all the resources. I have dug around and can't find concise answers on this question ... ...
10
votes
4answers
38k views

What is Frequency in electronics?

This has been floating in my mind for a while, everything has a frequency. Like a dc-dc converter, my scope is 100 MHz(i know that's a bandwidth but it has the unit of frequency). I understand that an ...
4
votes
3answers
14k views

How fast can a Transistor Switch?

An NPN Transistor can be made a switch by applying some power to the Base. Is there a limit to how fast I can switch the Transistor On and Off? Or I can switch it on and off as fast as i can turn the ...
23
votes
5answers
2k views

What are 12.000393 MHz crystals used for?

I found them on www.digikey.com, and they're apparently made by different manufacturers, so there must be some use for them. What are they used for? edit and why? The 2400 baud modem doesn't offer an ...
8
votes
2answers
3k views

Why aren't ferrite rod antennas used in WiFi?

Does it have something to do with soft ferrite's low coercivity, still not low enough at gigahertz frequencies? See, I'm putting together high gain receiver antennas and transmitter antennas. Space ...
8
votes
2answers
1k views

Is it true that the power line frequency is kept accurate by atomic clocks?

I've heard rumors that the power line frequency is kept stable and accurate by syncing it with atomic clocks. Is this true? What kind of accuracy does it have? Is this true everywhere?
2
votes
1answer
1k views

Specific frequency signal detector

How does for example a generic signal detector (E.G. this cellular frequency detector circuit) actually pick up on a specific range of frequencies? (for 4g im assuming its around 900Mhz?) In regards ...
0
votes
3answers
4k views

Operation of LC circuit in Frequency Modulation with simulation and linking it to the basic principle of frequency modulation [duplicate]

Can somebody help how message signal (words spoken near microphone) is modulated using LC circuit and how lc circuit oscillates at particular frequency by applying dc voltage. In the below circuit l1 ...
0
votes
1answer
5k views

How can i make a ceramic piezo operate at a specific frequency?

I recently just ordered several ceramic piezos used to aerosalize water and essential oils.http://www.aliexpress.com/item/Free-shipping-20mm-atomization-chip-board-dedicated-ultrasonic-atomization-...
6
votes
5answers
3k views

Bandpass filter to isolate musical note “A2”

I would like to design a bandpass filter to isolate the musical note A2 ( 110Hz ) from its neighboring notes at a precision of a half-step. This means that ...
6
votes
2answers
4k 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 ...
5
votes
1answer
433 views

Understand simple FM transmitter, inductance, resonance

I learn electronic , I try to understand this project, simplest FM transmitter : The project is describe here : https://makezine.com/projects/super-simple-fm-transmitter/ The inductance of L1 (Strip ...
4
votes
2answers
1k views

How does tuning in a spectrum analyzer actually work?

I have a pretty basic doubt about how tuning works in spectrum analyzers. I'm reading about the topic from Keysight's AN 150. The problem arises in this paragraph in page 11: We need to pick an ...
3
votes
3answers
228 views

Design help! — Play a pure tone into a mic and depending on its frequency a specific LED will light up

I'm still new to electronics and am making this in order to learn more about circuit design and filters. I do not want to use microcontrollers. I want a purely analog solution. I'm trying to make a ...
3
votes
2answers
5k views

QAM modulation - how data in different frequencies are laid out?

I know that QAM modulation uses a change in phase and amplitude to send data. But We use a series of frequency spaces as bandwidth to send data. However, we know that different frequencies oscillate ...
3
votes
2answers
3k views

Under what conditions does jw equal the laplace variable s in an electrical circuit?

Imagine I've got an electromagnetic actuator and solved the underlying differential equations. I got an solution for sinusodially excitation, as follows (just an example, no physical backround): $$G(\...
2
votes
3answers
8k views

Why do higher frequencies mean higher data rates, and why do we even need frequencies to begin with?

This is regarding wired connections. I have heard that higher frequencies mean higher data rates since there are more cycles per second you can fit more data in per second. That makes sense but I ...
0
votes
3answers
280 views

Why are ratios relevant, but not the increments when defining center frequency of a band-pass filter?

First of all, here is my directly related previous question: Why is center frequency of a bandpass filter is given by the geometric average of the two cutoff frequencies? Olin Lathrop explained very ...
0
votes
1answer
1k views

Open Collector Circuit Needs Pull-Up Resistor to Measure Frequency?

I need a little help determining what I need in order to measure frequency from an Encoder containing the attached Open Collector Output. The 5 Volts will actually be 24 Volts in my scenario (this is ...
5
votes
3answers
2k views

Very low frequency instrumentation amplifier

I'm trying to choose an instrumentation amplifier for very low frequency signals (seismic monitoring). The trouble I'm finding is that on many of the data sheets, they only give response curves down ...