# Questions tagged [frequency]

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

73 questions
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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?
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
1answer
310 views

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 ...
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 ...
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 ...
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 ...