# Tagged Questions

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

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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### How does RF anti-jam technology work?

I'm pretty certain that RF jammers work by overpowering the target signal with their own higher powered signal at the same frequency. So the question is, how does anti-jammer technology negate the ...
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### Frequency limitation for homebrew CPUs

While looking into some custom built CPUs I've noticed the frequencies at which they operate are relatively low compared to modern CPUs (in the order of several MHz). Is there an electronics ...
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### 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 ...
1k views

### Why is a lower switching frequency more efficient?

I'm designing a 10V to 3.3V step-down converter. Looking at the LT8610, the applications example shows two similar circuits that have different switching frequencies. The Efficiency vs Frequency plot ...
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### 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 ...
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### 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 ...
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### 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. ...
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### 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 ...
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### Is there a device that converts any AC frequency to 60 hz?

If I have something like a windmill generator that generates AC current, but at variable frequency, what device(s) would I need to convert that variable frequency into a constant 60hz frequency, so ...
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### 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?
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### MC34063A: Why am I overclocking this chip?

I've decided to get some experience with DC-DC converters and I've obtained an Onsemi MC34063A DC-DC converter. From documentation I've got the datasheet, the AN920 application note and the Excel ...
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### 4 Hz Stable Frequency generator

Whats a good circuit/design that will generate a very stable 4Hz signal (to feed into a counter) that won't drift with temp / time. It's not so important that its exactly any particular frequency, ...
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### Why can an oscilloscope only find frequencies 1/10 of the sampling frequency, despite Nyquist?

The oscilloscope at my university states both its sampling frequency and the maximum frequency that it can detect. However, the maximum frequency is just 1/10 of the sampling frequency! Nyquist's ...
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### What is the unit for resonant frequency?

What is the unit for resonant frequency? where $\omega_0 = \frac{1}{\sqrt{LC}}$? Is it just $HF^{-1}$?
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### 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 ...
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### Low “Hum” Frequency Detector

How do I create a frequency detector that can detect low "hum" sound? (quite low frequency sound probably made by a air-con or similar type of machine) Please feel free to ask me questions if my ...
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### 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 ...
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### 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 ...
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### What happens to RLC circuits at resonance frequency, conceptually

What occurs when $$\omega = \omega_r$$ The circuit frequency equals its natural frequency? So what. And why is it important?
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### 3-phase Motor Speed Controller

Background If you look at my profile description, you'll see that I'm involved in building and wiring up Carnival floats that are powered by an 800KVA, 415v, 3 phase Generator. Electrically, they ...
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### What limits the modulation of digital signals?

I am trying to understand why there are different speed on different frequency bands. I see that e.g. ZigBee can do 250kb/s for both 2.4GHz and 868/915MHz, but ...
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### Frequency Reuse Patterns

In Multiple Access Protocol for cellular networks, there is this Frequency Reuse Patterns. And I am given a formula to one of the patterns that states: $\text{Reuse factor }\mathbf{K} = i^2+j^2+ij$ ...
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### Astable multivibrator with increasing frequency

I am wanting to design a circuit that uses an astable multivibrator as a clock source. However the difference being that over time the clock is gradually sped up until it reaches some multiple ...
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### 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, ...
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### How to control Arduino frequency?

I'm porting a code from c in the Arduino platform (I'm using an Arduino Leonardo). I wanto to remote control a camera with an IR LED. The info about the remote control want to emulate here. The code, ...
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### Q factor for an LRC series circuit

Trying to prove to myself that the Q factor for an LRC series circuit is $\sqrt{L/C}/R$, but I am struggling with it... My reasoning runs that the half power upper frequency limit is (ignoring the ...
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### Rated frequencies and power requirements

(Here is a related, earlier question.) Two microprocessors are identically manufactured. However, after testing the two processors, the manufacturer bins, rates and labels them to operate at ...
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### 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 ...
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### What is the meaning of the nominal frequency specified by manufacturers of crystals?

This answer led to the conclusion that it is unclear what the meaning of the frequency listed by crystal manufacturers actually means. Given this graph on page 79 of this ECS Crystals Application ...
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### Common Analog Signal Frequencies

I'm trying to scope out what frequencies different common analog signals are. The DPScope design specs provides a list of common lower (sub 1 MHz) frequencies (copied below). audio (20 kHz) ...
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### Injection locked frequency dividers

I am beginning to design a monolithic frequency synthesizer (around 2.4GHz) in which I need the maximum of spectral purity. I was looking at injection locked frequency dividers (ILFDs) for use as a ...
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### Is Frequency for dc is zero?

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 notice, why cant that straight line be cut into smaller pieces, and ...
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### Interview Question, what's limiting the output frequency for the FPGA circuit?

I recently received a question in an interview that partially stumped me. It went something like this: You have an FPGA circuit that is supposed to be generating a signal with a frequency of 500MHz, ...
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### 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 ...
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### How do I modulate PWM frequency in realtime with a Microchip dsPIC?

I'm trying to change the PWM output frequency roughly once a millisecond using a dsPIC33FJ256GP710, and I'm having mixed results. I first tried this: ...
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### Connecting piezo buzzer with BJT

I have a 4 KHz piezo buzzer and a microcontroller (arduino) that outputs that 4 KHz from one of it's pins. All is fine if I connect the buzzer to the output with one pin and to the ground with ...
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### Are there any RF remote control circuits without any ICs?

I'm currently trying to make a simple 3 channels RF remote control circuit but without any ICs or micro-controller. I'm Googling but it seems to not populate (useful results). Does anyone have ideas?
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### Frequency response - finding transfer function

I have a this circuit: I am asked to find |H($\omega$)| in its simplest form. I approached the problem by first recognizing that the first op am was a standard inverter. With that I basically ...
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### 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 ...
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### How to Shift Carrier Frequency in QAM Signal?

If I wanted to apply a 100MHz frequency shift to a QAM signal with a 400MHz carrier frequency, I would Demodulate it at the carrier frequency Apply a frequency shift to the original signal Modulate ...
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### Odd number frequency divider

Important note: You are not helping me do my homework. This is for a competition for engineering students, that encourages you to "use your network" ;) I've got this pattern for a frequency divider ...
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### 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) ...