Questions tagged [noise]

About issues caused by electrical noise, or improving the Signal/Noise ratio of an analog circuit.

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30 views

Why does customer see high voltage on my PNP sensor output?

I have designed a capacitive sensor with a PNP output. The output stage is a Sziklai pair, as follows: simulate this circuit – Schematic created using CircuitLab While the circuit works OK, one ...
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1answer
28 views

Where do we place a Pi filter?

I have used pi filters in the past with the USB powers and it worked great. This time I need the pi filters to smooth out the 24V supply from a regular SMPS power adapter. There is a load switch/fuse ...
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3answers
49 views

Noise in an unconnected biopotential electrode lead wire

My question stems from a particular statement on page 256 of the textbook Medical Instrumentation - Application and Design, Fourth Edition (by J. Webster): Relatively high potentials can often be ...
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1answer
340 views

Bluetooth audio circuit noise problem

I am working with a bluetooth audio circuit. I am facing noise problems in the mic input so I used B0505S DC DC isolated module. It worked but now when I printed a PCB of the same circuit and I am ...
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1answer
69 views

esp8266 power supply problem

It's the fourth esp8266-12e that destroyed with my AMS1117-3.3 voltage regulator. I'm powering esp8266 with AMS1117-3.3 module and this simple circuit: ...
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0answers
95 views

Make audio signal go only one direction

I have a circuit in my car which emulates the protocol the radio uses to communicate with a CD changer. The goal of the emulator is basically to make the radio open up it's audio channels. The circuit ...
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1answer
235 views

Questions about a design for an SMPS post regulator filter circuit?

For minimizing SMPS ripple and especially noise, I’m trying to make a small interface which is a post regulator cascaded after an LC filter. I have come across some papers related to this topic and ...
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2answers
57 views

What is the maximum length a MC68030 can be placed away from Commodore CDTV motherboard, without affecting timings?

I want to fit a TF536 accelerator card into Commodore CDTV case, which is a challenge from the perspective of available space. I know there is a relocator board project available, but it still doesn'...
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3answers
52k views

Noise and what does V/√Hz actually mean?

Noise figures in (op amp) datasheets are expressed in V/√Hz, but Where does this unit come from? Why the square root? How should I pronounce it? How should I interpret it? I know lower is better, ...
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2answers
384 views

SDA pin on I2C lines seems weird

I am trying to analyze the I2C commands sent by a PC software to R3910 DSP chip The software uses a programming box (provided by the same company that manufactures the R3910 chip) to communicate ...
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1answer
42 views

“Noise” in simulator

I have been working on a simple circuit which performs XOR operation. The problem is that I am seeing a noise-like graph when both inputs are set to 1 (5V) and I have been doing a research on what it ...
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1answer
140 views

“To ground” or “not to ground” a coax to prevent RF ingress?

I have a communications system that connects a self-powered sensor circuit to a wall-powered processing/analyzing circuit by coax cable The coax reaches out about 60m, and it is matched/terminated at ...
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2answers
131 views

Noise in audio amplifier

I have built an audio amplifier using TDA2030. The amplifier works fine with very low noise, the input is given through 3.5mm jack of my phone. Everything works fine until I touch or pick up my metal ...
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2answers
43 views

Capacitive AC to DC power supply noise

Im using a transformerless capacitive power supply with this simple circuit: C1: 3.3uF 400V R1: 480K D1-D4: 1N4007 Z1: 10V 1W C2: 470uF But it burned some my ...
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1answer
253 views

What effect does a logic analyzer probe have on a circuit?

I have an MCU controlling a LED sign. This sign speaks the HUB75 protocol, which is essentially a large shift register. Being a shift register, this requires a clock signal to be generated, which the ...
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44 views

Filtering out Switching Noise

I'm designing a custom current limiting circuit designed for electric bikes and small electric vehicles. It's purpose is to limit battery current to "dumb" motor controllers so that you can ...
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1answer
284 views

How is this 50Hz noise coupled to the sensor and why does it disappear when wired in a particular way?

I'm using this amplifier with this load cell. There is a section in the amplifier's manual which states: First of all above terminal 5 in the amplifier's screw terminal which is called Screen/Ground ...
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2answers
85 views

Ultra low noise charge sensitive preamplifier

I developing charge sensitive preamplifier for radiation detector. This is a very sensitive device, the smallest amount of noise can completely ruin the signal. The schematic and the PCB you can see ...
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0answers
41 views

High frequency noise caused by a flashing LED [closed]

I have built a video production suite and I set up some "recording in progress" lights, to stop people wandering in when we are recording. I have also built a "push to talk" system ...
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0answers
54 views

I need help with making a ground loop noise isolator

I want to build a ground loop noise noise isolator for 3.5 mm audio jack. After some research online I found multiple circuit diagrams centered around using audio 1:1 transformers to isolate each ...
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2answers
13k views

Reducing LED PWM Noise: Which is the best option?

Driving an LED with a microcontroller should be easy. But when looking into noise, things can get complex... As an instantaneous voltage indicator used in a variable power supply (which will be used ...
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5answers
2k views

Is Gaussian noise equal to white noise?

If noise on a signal is randomly fluctuating in time domain around its mean following a Gaussian normal distribution (Gaussian noise), would this be equivalent to an constant intensity in the ...
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2answers
79 views

What is the origin of multiplicative noise from a DSLR sensor?

I'm trying to understand the behavior of my DSLR camera sensor (Canon 80D). I've taken a picture of a gradient from top-right to bottom-left corners of a square. This square is positioned at the right-...
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0answers
51 views

Speaker and player on same 5V charger crackles but not with two separate chargers

I am using a Samsung mobile phone connected to an external speaker (connected via a standard audio cable with jack connectors). Audio is playing fine when I use two Samsung-branded 5V-DC chargers, ...
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4answers
10k views

Loud pop noise while plugging to a headphones jack

I have a Panasonic RX-ES29 boombox with a type C plug (ungrounded). I sometimes hear a relatively loud snap/pop sound in the right speaker of my headphones while I completely plug them into the ...
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3answers
83 views

Is there a limit to the number of inputs that can be summed with an op-amp summing circuit?

I'm interested in the limits you encounter if you try to add many inputs into an op amp summing circuit. I've read that the inverting configuration is more natural for adding many inputs since the ...
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1answer
285 views

Common mode chokes in series

I am designing an ultralow noise audio board. On the first PSU PCB (just talking after bridge) I have a CMC to remove switching noise on diodes to undetectable levels (with plenty of capacitance for ...
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0answers
20 views

Bluetooth Receiver Board - Noise Problem

I recently bought a bluetooth receiver board in order to add bluetooth to my car, this however is not as easy as I thought. I am not very skilled with electronics. I have an aux audio input in my car ...
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1answer
35 views

How to prevent switching direct and/or inductive noise on a PCB?

I'm designing a power source for one of my projects and I couldn't find a better way to reduce the voltage drop on 7805 regulator other than using a switching regulator (LM2596). The switching ...
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8answers
6k views

Is it possible to receive information if the received power is below the noise floor?

This relates to my previous question, which I think I have asked in the wrong way: How to insert background EM noise into pathloss equation? I wasn't really interested in detectability of the signal,...
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2answers
65 views

How can picked up FM noise be demodulated?

I have a set of cheap computer speakers, which happens to use a TDA2822M. Its circuit is almost identical to the example circuit from TDA2822M's datasheet. It's USB powered and has no shielding. I ...
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1answer
29 views

Power interference when turning on speakers, causing monitor to go black

I have a small 2.1 external speaker system that I use with my laptop. I also have an external monitor that I use with the same laptop. Almost every time I turn on or off the speakers, the external ...
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0answers
44 views

Analog differential signaling

I'm a software engineer that sometimes has to deal with some electronics. So I'm by no means an expert... I want to control a BLDC motor and I have added a thermistor to the windings of the motor so ...
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2answers
279 views

“Creating” a ground pin for my laptop

I am building a sensor using an Arduino connected to a laptop; I noticed that the readout is much more noisy when I use a non-grounded laptop (either running on battery or connected to a power socket ...
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1answer
81 views

Noise with TPA3110D2 amplifier on the same power supply as an USB HUB

I have a TPA3110D2-based, XH-A232 amplifier board powered by a 12V switching supply (S-120W-12V). The input is the headphone output of a monitor connected to a PC. I would like to power an USB HUB ...
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1answer
153 views

Signal noise cancelled by touching the leads

I have a pressure sensor that outputs 0.5V with a +/- 20 mV noise. I am trying to identify the root cause of the noise using an oscilloscope. The noise occurs in waves of twice the mains frequency, ...
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2answers
4k views

mV variations even with a simple voltage divider

edit: After using a prototype pcb instead of breadboard, placing all possible electromagnetic sources away and unplugging all the equipment from the same line, my noise dropped 2 orders of magnitude. ...
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2answers
64 views

How can thermal electrical noise be uncorrelated yet appearing at a certain frequency?

Say we look at the thermal noise spectrum of an ideal resistor. Now we know it will behave like $$ \langle U^2 \rangle = 4 \, k_B \, T \,R \,\Delta f $$ We also know that two subsequent voltages ...
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1answer
157 views

Phase-modulated Noise

If you replace the carrier signal in a phase modulated circuit with noise then presumably the noise will be modulated. What must be considered if we wish to detect this noise modulation? I’ve ...
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1answer
197 views

Thermal Noise in Oscillators

let's consider this circuital model for an LC oscillator in which the parasitic resistance R is affected by thermal noise (represented here with an equivalent noise current source, according to the ...
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1answer
111 views

Purpose/Difficulties of having a common mode choke

This question is related to common mode choke. I know I have asked this question a couple of times in this forum and I have also read related questions and answers. But I am not able to get the total ...
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2answers
45 views

Power rail noise calculation

I am attempting to calculate the noise on the power rail that my ADC is receiving so I can calculate my effective number of bits. But the different units on the datasheets of the regulators are ...
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2answers
57 views

Audio: Digital Potentiometer is Noisy Compared to Analog Potentiometer

I am building an A/V switch that I would like to have a headphone output with adjustable volume, controlled by a microcontroller. As a test, I connected an audio source to a potentiometer (input to a, ...
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1answer
159 views

Filter VR-sensor to MAX9926

I have an issue with a noisy VR-sensor signal that my MAX9926 IC isn’t managing to interpret correctly, and instead outputs rubbish. The wheel that’s being used has one long tooth and one short. Here ...
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2answers
533 views

How to filter out in-band noise at the same level as my signal?

I'm implementing a system wherein I'm detecting waves as they come trough my piezoelectric sensors in a board. Essentially, I would want to record the time these signals appeared in my sensors as I ...
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1answer
246 views

getting noise when connecting speaker out of sim800l to raspberry pi

i was trying to make a roaming device which helps me route my calls through internet, to save my bills while on international roaming. my setup goes like this: gsm module sim800l, raspberry pi4, a ...
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0answers
49 views

NPN condensor mic pre-amp really noisy

I have designed a pre-amp and I am having a lot of noise when silent. It seems to be around 70 Hz on my scope, but jumps around. I've tried adding bypass filters on the NPN emitter legs, as well as ...
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17 views

Noise Temperature to Noise Factor

If I have a noise temperature of (I'm not sure how to do subscripts) Te = T1 + T2/g1 and since Te = (fn-1)To. I believe that fs = f1 + (f2-1)/g1 But I'm not sure what the steps in between these 2 ...
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2answers
95 views

How to get rid of 19kHz electrical fields

The mains of my German flat has 19kHz electrical fields on hot, neutral and! ground wire. I don't have to get rid of them entirely but I want to achieve 20dB reduction while sitting in front of my ...
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1answer
35 views

Op-amp noise figure

If I have an opamp such as LM324 or a voltage regulator. How can I obtain noise figure experimentally? For the opamp I would apply DC input and the ratio of output SNR to input SNR would be noise ...

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