# Tagged Questions

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

1answer
105 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 ...
1answer
76 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. ...
2answers
155 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 ...
0answers
71 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 ...
1answer
117 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?
1answer
134 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) ...
0answers
11 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 ...
2answers
108 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 ...
2answers
531 views

### Relation between Power consumed and MCPS (million cycles per second) consumed on a processor

I have been working on a ARM cortex A8 board on mp3 decoder. While doing this I have a requirement saying the mp3 decoder solution I am doing should consume 50mW. This generated few questions in my ...
1answer
138 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 ...
2answers
509 views

### For a nerve-teste circuit, what causes the shock at low voltage?

As a bit of a weird test for my new 555 IC, I have been thinking of stepping down a 9V PP3 battery to five or so volts and creating a square wave @ ~100Hz and shocking my finger. I understand that a ...
2answers
207 views

### How can i know the frequency range of electronic device?

How do I know the frequency of an electronic device? For example, we all know that the microwave is working under 2.4 GHz frequency. So, if I want to know the other frequency range for other devices, ...
1answer
58 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 ...
1answer
121 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 ...
2answers
69 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 ...
4answers
1k views

### Why all digital signals have infinite bandwidth?

Why digital signals have "infinite bandwidth"? Frequency is the number of cycles per second. I have seen before the formula that bandwidth=Maximum Frequency - Minimum Frequency. I remember I was told ...
1answer
86 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 ...
2answers
71 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. ...
1answer
120 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 ...
2answers
156 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 ...
2answers
962 views

### 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 ...
2answers
390 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 ...
2answers
247 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 ...
2answers
451 views

### How Does FM Get Around the Gabor Limit?

The Gabor Limit states that it's impossible to simultaneously localize a signal in both frequency and time. FM communication modulates the instantaneous frequency of the carrier in step with changes ...
1answer
246 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 ...
6answers
684 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
372 views

### 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 ...
2answers
227 views

### 380-385 Mhz band-pass filter (SAW?) [closed]

I am relatively new to the world of electronic components, but I've been trying to learn for a while now and I understand most of the logic behind simpler designs. Now I'm trying to build a filter. ...
1answer
82 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). ...
5answers
406 views

### Frequency of audio signals taken from multimeter

So I grabbed my Fluke True RMS multimeter yesterday and plugged it in to my Samsung Galaxy Note's audio jack, and started to play some music. I saw AC voltage frequency around 0 – 15 Hz (it's ...
2answers
153 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 ...
3answers
212 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 ...
2answers
228 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 ...
3answers
249 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, ...
2answers
194 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 ...
1answer
240 views

### What is CLK in UART/USART used for?

I'm studying computer architecture at my university and I've been recently asked a question: what is CLK used for in UART/USART? The first obvious thing is that it is used for dividing frequency when ...
2answers
850 views

### Highest ADC input signal frequency for atmega8?

I am trying to make a simple project which involves acquiring some data from the adc of atmega8 chip and then sending that data to UART. But I cannot figure out what would be the maximum limit of the ...
1answer
857 views

### 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?
3answers
4k views

### 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: ...
1answer
711 views

### 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, ...
2answers
452 views

### Why output of square wave signal after bypass capacitor is a triangular wave?

I understand square wave contains many sine waves of different frequencies as so does triangular wave. My impression with bypass capacitor is that the higher the frequencies the better it attenuates ...
1answer
172 views

### Generate a 200kHz varying voltage signal

I have a 12V DC supply from just a normal household converter. We have to make a circuit which will output an 200kHz AC signal with a p2p voltage of 3-12 volts depending on a strain gauge. 3 being no ...
5answers
446 views

### 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 ...
1answer
124 views

### For the sum of two sinusoids, let the frequencies of the individual terms be f1 and f2, respectively [closed]

For the sum to be periodic, f1 and f2 must be commensurable; that is, there most be a number fo contained in each an integral number of times. Thus, if fo is the largest such number, f1=n1*fo and ...
3answers
78 views

### Close a circuit at specific input frequency

I have several very simple circuits comprising of a battery connected to a LED. Additionally I have an input signal at some frequency, which I need to use in order to control these circuits. What I ...
1answer
127 views

### Toggling problem of D flip flop [closed]

how to do frequency divider by 2 without having the toggling issue ? Since I just want to divide the frequency by half and align that signal with single pulse signal.
0answers
239 views

### How do I modulate PWM frequency in realtime with a Microchip dsPIC (or PIC24)? [closed]

This question is a direct continuation of the question/answer found at the link below. Skip to the last answer/comments given, as this is where my question begins (I don't have enough rep. points to ...
1answer
217 views

### 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 ...
2answers
221 views

### 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 ...
2answers
207 views

### Does the weight of a mass effect the transfer function of a vertical mass-spring-damper system? [closed]

Usually in system dynamics, I dealt with horizontal mass spring dampers. Now in my advanced class I am dealing with vertical mass spring dampers. So a spring is hanging from the ceiling with a mass ...