How many times something happens per second, measured in Hz (Hertz).
4
votes
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.
...
3
votes
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?
0
votes
0answers
74 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 ...
0
votes
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 ...
3
votes
2answers
109 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
140 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
106 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
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 ...
-2
votes
1answer
123 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
135 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
70 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
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 ...
0
votes
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.
...
1
vote
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 ...
0
votes
2answers
399 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
248 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
254 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
685 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
167 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
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).
...
0
votes
2answers
162 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
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 ...
4
votes
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 ...
5
votes
3answers
250 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
230 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
196 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 ...
3
votes
1answer
243 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 ...
3
votes
1answer
864 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?
1
vote
5answers
409 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 ...
5
votes
1answer
719 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, ...
0
votes
2answers
455 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 ...
11
votes
5answers
447 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 ...
-1
votes
1answer
125 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 ...
0
votes
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 ...
2
votes
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 ...
-6
votes
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.
5
votes
1answer
218 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 ...
1
vote
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 ...
4
votes
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 ...
2
votes
2answers
212 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 ...
3
votes
3answers
647 views
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 ...
4
votes
2answers
1k views
Problem with a Relaxation Oscillator (using Op Amp)
I'm studying a relaxation oscillator. This wikipedia circuit shows exactly my circuit with the only difference that I'm using different values for each resistor.
I called resistor R the one ...
1
vote
1answer
465 views
Resonant frequency of piezo elements, and generating multiple tones
In another question I posed, there were couple of "piezo sounder" parts suggested for the purpose of a compact but reasonably loud, alternative to electro-mechanical hooters.
Was trying to understand ...
2
votes
0answers
166 views
Decoding 125kHz ASK signal [closed]
I'm looking to decode what seems to be a 125kHz ASK amplitude shift keyed signal (1 V p-p). I'm saying ASK, but it may not be the right term. It's basically a 125 kHz signal or a 1V constant voltage. ...
5
votes
2answers
161 views
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 ...
1
vote
4answers
271 views
Computer bus frequency and electricity frequency
From http://en.kioskea.net/contents/pc/bus.php3
A computer bus is characterised by the amount of information that can be
transmitted at once. This amount, expressed in bits, corresponds to
...
16
votes
5answers
695 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 ...
11
votes
2answers
551 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 ...
5
votes
4answers
317 views
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)
...
1
vote
1answer
92 views
frequency modulation
I hope this is a pretty easy question for you guys.
I know for frequency modulation (FM) for fundamental frequency you have the expansion
$$output = J_0(\beta)V\cos(\omega t)\pm ...
