# Questions tagged [signal]

A signal is a stream of information in the form of a varying quantity. Usually in electronics, signals can be in the form of voltages, currents, or radiated electromagnetic fields.

1,888 questions
Filter by
Sorted by
Tagged with
60 views

### Capacitor in series with a button

I'm working on making my old Lift Master / Craftsman / Chamberlain garage door opener 'smart'. The original control panel uses two wires at 22 volts to control 3 functions - door toggle, light toggle, ...
• 131
121 views

### Controls - seeing if a discrete time system can arrive from a certain input to a certain output

Given a system: $$A = \begin{pmatrix} 7 & -3 \\ 18 & -8 \end{pmatrix} \quad B = \begin{pmatrix} -2 \\-6\end{pmatrix} \quad C = \begin{pmatrix}1 & 0 \end{pmatrix} \quad D =0$$ I need to see ...
1 vote
88 views

### 'Strange' behaviour due to DC motor

TLD: How do I minimise noise / electrical disruptions created by a DC motor? Situation I would like to control a DC motor through DMX512. Therefore I connected a Max485 chip to an Arduino to receive ...
• 21
86 views

### How to calculate a differential + common mode LPF circuit?

I'm trying to validate my understanding of a differential + common mode LPF circuit using the AK4499EX datasheet (019001308-E-00 2022/07 version, p. 47). It presents the following circuit: and its ...
69 views

### Decoding unknown serial data from treadmill console board

I have been working on a treadmill project whereby my aim is to manually control the treadmill with an Srduino without using the remote. Info about the treadmill - The treadmill is just a normal ...
88 views

### Why is my encoder showing abnormal spikes on the oscilloscope readings? Any suggestions on what might be causing it?

So to summarize, I have these winch drives that I've put together. One of them went berserk during testing and now I'm diagnosing the problem. I have attached an oscilloscope to where the KEB servo ...
1 vote
187 views

### SPI device stops working when integrating Schmitt triggers and ESD diodes

I am integrating a BME680 temperature, pressure and humidity sensor using SPI. When I only use 33 Ohms series resistors, the system works fine. However, when adding Schmitt triggers (NL27WZ17DFT2G), ...
• 179
69 views

### Localized interference between 2 distant points [closed]

Lets say an emitter sends a directional carrier wave of 60 Hz that can travel up to 100 km. Then, at 50 km from source, another weaker wave of 60 Hz is emitted. This weaker wave is off phase compared ...
396 views

### Why do PALs have higher speed than PLAs?

When considering speed I have learned that PLAs are much slower than PALs. As each signal has to propagate through same sequence of gates (in series) why there is a speed difference?
39 views

### How do I relate input and output signals and find the output for other input signals in LTI system?

I am studying about signals and systems. I came across a few practice problems. For the below question, I was able to mimic the input and output waves shown in ...
• 161
155 views

### How do I represent a signal as the real part of complex exponential and find the value of complex amplitude & complex frequency?

Context: I was solving some practice problems and came across this problem. I know the complex exponential is: $$s(t)=Ae^{i({\omega}t+{\phi})}{\Rightarrow}Ae^{i{\phi}}e^{i{\omega}t}$$ Where \\$Ae^{i{\...
• 161
1 vote
63 views

### Is my understanding about the ECG waveform is correct or not

I need to design an amplifier for an ECG signal.The signal specification is given below. BW = 0.47Hz..40Hz (-3dB) – Limited by the system Signal amplitude max. 10mVPV (peak-to-valley), DC offset max ±...
• 2,593
57 views

### ROC of Laplace Transform of a time shifted impulse signal

If x(t) is of finite duration and is absolutely integrable, then the ROC is the entire s-plane. This is stated and proved formally in the book of signals and systems by Oppenheim in the context of ...
49 views

### Interdependency Issue in Power Enable Circuits for Sensor and Modem Controlled by STM32L476RG

I have designed a power enable circuit to control the power supply to both a sensor and a modem, each with its own dedicated power enable circuit. The MCU used is the STM32L476RG, and the power enable ...
22 views

### Determining Suitable TRMS Voltmeter Specs for Modulated Signal Measurement

I'm seeking advice on selecting a TRMS (True RMS) voltmeter suitable for measuring the voltage across a resistor with a modulated signal. Here's the scenario: I need to measure the TRMS voltage across ...
101 views

### Layers/Pours and other Good Practices for 2-4 layer PCB (Audio Amp 250V)

Started working on my first PCB (guitar amplifier) and so far have just roughly placing a few of the components and ran some tracks that I've color-coded based on purpose, not necessarily the layer ...
• 53
5k views

### Which signals (Wi-Fi, mobile phone, and GPS) can reliably be blocked by aluminum foil?

There seems to be conflicting information regarding which signals can be effectively blocked by wrapping the device in aluminum foil. With effectively blocked I mean block the signal as such that the ...
74 views

### What is the appropriate VCC to apply to a Schmitt trigger?

I would like to transport a SPI signal over 1 meter, at a 10 MHz clock rate, with each SPI wire twisted with a ground wire, no differential signal, 33 Ohms terminations, ESD protection with chip ...
• 179
946 views

### Why is a Schmitt trigger useful for SPI?

I understand Schmitt triggers are a great way to convert a floating or noisy signal to either HIGH or LOW depending on a threshold. It is mentioned in other threads that a Schmitt trigger can help ...
• 179
45 views

### Designing a reed switch circuit

I have been trying to design a door contact sensor. Almost 90% is completed, but I am confused about this reed switch circuit. The problem with the circuit is it is consuming too much current I am ...
1 vote
88 views

### Power amplification: from square signal DC to AC square signal

I'm currently developing a circuit to amplify a square signal originating from a PLC. The frequency of this signal ranges from 1 Hz to 20 kHz. The load consists of a small resistance, almost ...
121 views

### WHY does the LED turn on SLOWLY?

TL;DR ver: LED light controlled with Arduino lights up during an interval of 2 frames, not one in a video footage of 30 FPS. It slowly turns on... but why? ===== I have a (mouse) behavioral experiment ...
33 views

### Unilateral laplace transform of rect(t/2)

What would be the unilateral laplace transform of rect(t/2)? We know that rect(t/2) can be written as u(t+1)-u(t-1).So what would be its unilateral laplace transform? Should it be (exp(s)/s)-(exp(-s)/...
58 views

### Integration of signal [closed]

How can I solve this integral? I know this integral is equivalent to convolution with u(t). Hence the convolution of u(t) with u(t) is r(t) or ramp function. But what would be the convolution of u(...
60 views

### Voltage regulating circuit for high frequency signal

I have a running circuit with an AD9833 to generate a sine wave with a desired frequency and phase, now I also want to digitally (not just a mechanical potentiometer) control the amplitude. The output ...
1 vote
82 views

### Is this the correct way to make a bandpass filter?

I'm trying to make a bandpass filter for a low voltage noisy electrical signal coming from a K-Type thermocouple To identify the frequencies I would need to filter out, I make a spectrum diagram using ...
66 views

### What is minimal frequency to detect such signal? [closed]

I develop simple signal generator, to debug other devices. It sends high logic signal which has length approximately time length 64 microseconds. If i connect some device which has processor frequency,...
62 views

### Was there ever a protocol to send profanity censorship tones out-of-band over television, so that viewers could turn them off? If not, why not? [closed]

These days, in the Western world, closed captioning is delivered out-of-band, so the captions are not actually part of the video itself, allowing viewers to turn them off if they are not desired (...
• 97
1 vote
189 views

### How does a signal get amplified? [closed]

Say I send an analog electric signal through a telephone wire. If that wire is long enough then the resistance will eventually make the amplitude of the signal close to zero. How do electric signals ...
• 349
1 vote
80 views

### Proof that two systems are equivalent

I was wondering if someone could help me with the proper answer for this? Below is the question and my solution. I was hoping for partial points but I don't know what can be marked partially correct ...
• 11
78 views

### How can I use MATLAB to show that the Doppler effect destroys orthogonality of OFDM subcarriers?

I am trying to get a visual representation of how the Doppler effect destroys the orthogonality of the subcarrier and understand this effect. I plotted three orthogonal subcarriers in MATLAB: ...
57 views

### Processing data from optical chopper to correct for drift

I have a time series measurement of light intensity where the signal is periodically blocked by hardware to provide a moving baseline to correct for drift. This looks like a square wave, where the ...
• 21
1 vote
35 views

### Why does the volume of the preamplifier change when a second audio signal is mixed? [duplicate]

I have two audio signals leading to the amplifier input: the first one comes from the preamplifier, the second one from the audio output of a smartphone/tablet device. Both have a resistor and a ...
• 53
64 views

### 3x analog signal multiplier

I was looking for sin(x) in, sin(3x) out. I am aware of PLL, diode, and AD632 multipliers. Most are either squarers for sin(2x) or pure sine or amplitude multipliers. I saw the sin(a+b) identity and ...
91 views

### How to switch between two signals with a digital signal?

I have two different potentiometers. Each sets different voltage reference signal for a current source. How can I make an Arduino or any digital signal to switch between these two potentiometers? (No ...
89 views

### Why do resistances disappear when studying variations of the voltage Va?

I'm trying to solve the question 2.2 of this sensor conditioning exercise. In the solution of the exercise, when trying to find Δ va, the teacher made the resistors R, and the continuous voltage ...
44 views

### Z transform and the magnitude of Fourier transform

Would like to know if the graph of the magnitude in the picture I added is correct. Should I address the other pole?
646 views

### Recreate an inline 12 Volt Electronic Flasher unit for LED turn signals

I am trying to recreate the circuit for a TWO PIN 12 Volt Electronic Flasher unit for LED turn signals. It is the inline flasher "relay" that I need. Where power comes in the B (Battery) pin ...
• 124
27 views

### Cold junction temperature measurement in Multichannel Thermocuple

In a multi-channel thermocuple signal conditioner (for example, 5 channels on a single PCB), should I add 5 separate junction temperature measurements to the thermocuple input of each channel to ...
• 756
40 views

### Generating sine, triangle (etc) waves from ttl output of a GPS module (Ublox)

I'm building a variable frequency standard using a Ublox gps board off Ebay. It'll be hooked up to an Arduino and you enter the desired frequency via a keypad. The signal from the module is a square ...
1 vote
81 views

### 24 VAC signal rectifier and detection

One of my projects consists of recovering a 24 VAC signal to give a run command. To avoid using a relay with a 24 VAC coil I would prefer to convert the 24 VAC signal into a DC signal and use an ...
• 41
226 views

### What is the purpose of the op-amps connected back to back in a thermocouple signal conditioner?

I am trying to design a thermocouple signal conditioner. I came across this structure on the Analog Devices LTC2057 typical application page. Why was such a connection made instead of using a single ...
• 756
82 views

### How can I trigger a 3V relay with no current, just a 3V signal?

Is it possible to trigger a 3V relay with a 3V signal voltage carrying no current? I want to be able to operate a 12V ebike lighting circuit via the brake lever which also operates the motor cut off ...
184 views

### Why do some circuits work in LTspice, but not in Proteus?

Why do some circuits work in LTspice, but not in Proteus? I was playing with my amplifier circuits in LTspice by changing the values forth and back, I had calculated. I was thinking about a special ...
53 views

### Signal Generator Output Impedance Matching and Floating Ground

I am attempting to recreate a signal generator circuit based on the XR2206, as seen in this video. The schematic uses op-amps for offset cancellation and output amplitude matching. To avoid the need ...
• 45
206 views

### Why does 'Rfb' affect input impedance?

I am reading "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin published by the ARRL. On the topic of feedback, see that two methods are presented. One method is emitter ...
129 views

### How to find the strongest frequency in a signal using a microcontroller/circuit?

I am trying to implement a low-power backscatter transmitter+receiver and ran into some trouble on the transmission side. Setup: My transmitter circuit sends a 50MHz wave, which the receiver circuit ...
58 views

### Do I need to edge instead of set a pin that is considered a "strobe"?

I am trying to get the NHD-320240WG display to run using my 8 bit hobby computer. I have successfully gotten this display to work with an Arduino and have ported the code to 6502 assembly. When ...
1 vote
220 views

### Clock Signal over long distance

I'm building microphone array using 16 ICS-52000 MEMS microphones and I propably have problem with clock singal because of the long distance. Below is output signal of the 8 microphone I have already ...
• 41