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

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38 views

Design a low-pass RC circuit to eliminate SMPS noise

As per a previous question I've asked - trying to track noise from a circuit. I've built a audio relay switch and the audio path seems to be inducting noise from the relay power supply (shared ...
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1answer
66 views

Clean DC power supply from a dirty souce

I'm building a guitar pedal which uses a series of relays to switch various signals. The relays are currently being powered by a cheap 5V switchmode supply and the audio path is inducting high ...
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2answers
73 views

OpAmp: Better to actively attenuate, or drive full range into a divider?

I want to get a +-15V differential signal (60Vp-p) into an ADC that has a single 3.3V supply. When I asked a friend to proofread it, he was concerned about the noise performance of R5-R6 vs. using ...
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2answers
145 views

Arduino - How do I reduce the noise in my circuit

I have a fairly simple circuit consisting of an arduino an accelerometer and an amplifier. I am collecting data from the accelerometer using I2C and playing some sounds through a switching amplifier ...
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31 views

Long range PIR sensor circuit

I would like to develop a long range motion sensing circuit. I have done some research and the most cost-effective solution seems this. This approach is based on the use of more PIR sensors. However ...
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4answers
115 views

How to select gain for an amplifier before ADC?

The circuit has been simplified as shown in the picture. Signal source is connected with an analog amplifier, which amplifies the ac signal and also raise it by 1.5V to match with the range of the ...
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1answer
64 views

How does the power supply noise generated by digital ICs affect the output of regulator?

I have learned that the digital ICs would generate the power noise in the power supply line,however, I am not so clear about how. In my opinion, two contributors: the change of the current would lead ...
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41 views

Antenna to reject 5.8Ghz Interference

I live a couple miles past where "normal" high-speed internet is available, and for years I have used a radio WAN link on a 70' radio tower to connect to my ISP in town, 4.65 miles away. I have a ...
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1answer
53 views

Resistance of a Wheatstone Bridge

In the Whetstone bridge circuit: If the circuit is balanced (and all resistances known), and we measure Vg as a function of time, then the fluctuations correspond to $$4K_bTR$$ the well-known ...
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1answer
52 views

Emf interference on arduino and breadboard , using 74HC595 shift register, how to prevent it?

I’m using a 74HC595 chip (shift register) NPX semiconductors, connected to and arduino board. Basically the shift register switches on and off 8 leds in sequence. Everything seem to be working, code ...
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1answer
42 views

How can the Nyquist theorem for the maximum bit-rate of a noiseless channel be derived?

I've been given the formula: $$ I = 2* H * log_2(L)$$ where: \$ I \$ = Maximum data rate in bits per second for a noiseless channel \$H\$ = Bandwidth that the channel will carry (that is, the range ...
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2answers
64 views

How to eliminate 50 Hz noise from amplifier's output

My goal is to amplify signals with a frequency from 100Hz above. My circuit is looking as the picture below. With an oscilloscope, I am trying to measure the output of the amplifier. If the input of ...
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2answers
72 views

High speed MOSFET switch noise

So I have PWM signal controlling an N-FET switch at around 20kHz. While it works in theory, in reality it takes longer to switch the MOSFET off. I assume it is because of output capacity parameter? ...
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2answers
63 views

Earth connection missing on electric circuit, getting lots of noise with audio equipment

I have a question today that possibly crosses to another website, but i'm interested in your expertise here. It's more or less about music, but also about noise and electric current. Basically, I ...
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1answer
189 views

How can I fix a “singing” capacitor

There is a 332 1kv ceramic disk capacitor in a battery charger that I use on my desk. The capacitor emits a very high frequency and headache-inducing "singing" noise. I understand that this is normal ...
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1answer
58 views

Sanity check: Input and output filter for a stacked pair of DC/DC converters

In my current project, I need voltages of +/- 30V and +/- 15V for analog control purposes. The current on the 30V rails is fairly limited, ca. 70mA max on one rail and <10mA on the other. The 15V ...
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1answer
84 views

Calculating noise power spectrum

I have some signal which I have measured N different times and I want to calculate the noise power spectrum of it. Intuitively to me the way I would do this is simply calculating the power spectrum of ...
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34 views

Sigma Delta ADC code fluctuation

I am designing a precision Pressure calibrator using C8051F350 MCu with inbuilt 24 bit Sigma-Delta ADC(I need only 16 bit performance). I have interfaced my sensor's differential output directly to ...
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2answers
56 views

Noise Gain of Op Amp

Why do noise gain of op amp is always constant ( 1+(R1/R2) ) and independent of configuration unlike Signal gain?
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51 views

How to reduce line noise on oscilloscope?

I bought an oscilloscope, and wanted to try it out at home. However, when I plug a probe into a channel, and the power into the plug of my workshop room, I see the 50 Hz line noise from the power ...
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1answer
155 views

Comparison of Series and Parallel LC Filters for Noise Reduction

Since there are two basic types of LC circuits that can be used for passing/blocking signals, I'd like to know the differences when using series or parallel LC circuits for noise at a known frequency. ...
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1answer
207 views

Why do they separate some parts of PCBs through making wide holes? [duplicate]

I have seen several PCB that they have wide holes in some their parts (especially the supply of circuits parts). for example take a look at this picture: and on the board: Not sure but I think ...
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2answers
74 views

Are there other ways in which 60Hz noise can get into your system?

Are there are other ways in which 60hz can get into a system other than ground loop ?
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1answer
40 views

What would be the peak voltage value of two combined signals (one noise and one sinusoidal signal)?

As I learned before, the peak voltage value of two combined sinusoidal signals is the sum of the two amplitudes, for example, \$0.6\sin(ax) + 0.8 \cos(bx)\$ can be \$+1.4\$V or \$-1.4\$V. Would it be ...
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1answer
62 views

Is there any offline circuit simulator software that can simulate a noisy power supply?

I have been using Circuit Wizard (Its the only offline program that I can find!). Unfortunately, it is really basic, and I have outgrown it. I need to simulate a 5V circuit with a noisy power ...
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32 views

Measuring RF Noise of Electric Train

I live near an old electric trolley, and I've noticed that it apparently interferes with RF signals. In particular: I notice that when I drive next to the line my satellite radio drops out. My ...
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2answers
165 views

Ethernet 25 MHz and 50 MHz harmonics cuases radiation emission during the EMC lab test

My PCB has been suffering with 25 MHz and 50 MHz harmonics radiation emission. I am using STM32F207 microcontroller operating with 8 MHz crystal. I am interfacing MAC in microcontroller to PHY ...
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56 views

Switching Power Supply makes speakers hiss

I have a computer with a 5.1 soundcard, that I'm using to run a standard PC 2.1 setup (Corsair SP2500) on the main audio output, and two rear surround speakers I had laying around. The speakers in ...
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1answer
107 views

Difference between SINR SNR

I am bit confused between these two terms. I understand SINR is signal to interference+ noise ratio and SNR is signal to noise but isn't interference noise too? Then why have he segregated these two ...
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1answer
105 views

DIY wifi radio radio NOISE!

I am building a mono, internet enabled, WiFi radio and I have a problem. I am running into what I believe may be a grounding issue. When I turn the system on, I hear all kinds of noise coming from ...
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2answers
111 views

Linear regulated supply from noisy input voltage

I have been working to redesign a faulty circuit board. One of the problems I have identified is the power supply on the board. The input voltage is nominally 13.8V DC from an AC switchmode ...
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1answer
31 views

Noise calculation for ADA4528

I thought I got familiar with noise calculations and RMS nv/rthz conversions, hence I went forward to test my understanding. I am comparing some opamps based on their noise levels. So I wanted peak to ...
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82 views

Noise-cancelling headphone concept

Inexpensive noise-cancelling headphones use a single microphone located in a little lump between the plug and the earphones. They seem to work fairly well for ambient noises, but not for handling ...
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1answer
133 views

Noisy Voltage Rails (Vcc, Gnd) - Noise Isolation for Automotive Circuit

I have an audio (mic, speaker) circuit that I am currently powering off of a 12V car adapter that is fed into a 10V switching DC regulator to power the rest of the circuit. I have noticed a horrendous ...
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3answers
59 views

Correlation and filtering

I am trying to get an understanding of white noise and how it can be filtered out, etc. For that I'd like to understand correlation. What would the autocorrelation of white noise look like? If I am ...
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1answer
122 views

50 Hz noise problem in isolated AC-DC power adapter

I have a circuit which is powered using AC-DC 12V wall converter. One of the power supply adapter has ground pin (3 pins) in its input and the other doesn't have (2 pins). The ground pin in the first ...
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1answer
63 views

Decoupling pair of microphones using noisy power source

I currently have a high quality microphone that I am powering from a relatively noisy 8V source, like that shown below. It has a built-in amplifier, and doesn't require any amplification. It just ...
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2answers
41 views

Measuring band-limited noise coming from an amplifier

I have a strain gauge amplifier and from my analysis, it will produce a low level of white noise above approximately 1kHz i.e. the power spectral density is flat above 1kHz. If I measure the output ...
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2answers
132 views

Issue of power line noise

I am laying out PCB for a stopwatch project that I made couple of months ago. I seem to have taken care of the only sensitive part i.e. crystal, since it is time measuring device. But I also see that ...
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2answers
161 views

What are the major sources of noise in a system

This question is a follow up on the question about the inductor choice for power supply noise filtering. One of the inductor's parameters was frequency response curve. To use this, I would need to ...
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2answers
163 views

Inductor selection for obtaining a noiseless analog power rail

I interface an image sensor, and the design schematic for power supply is: How do I choose one from the available 3uH inductors based on the specs? I figured the maximum current and dc resistance ...
4
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3answers
207 views

What causes old power supplies to start humming?

I have a number of mains-powered devices that have begun humming (I assume at 50Hz, though I haven't measured it). These include clock radios, a speaker system, a lamp (20W halogen with a transformer ...
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5answers
111 views

How do metal cases work with connectors & isolation?

I have troubles understanding how do metal cases behave in some cases. Case 1: I made passive attenuation box for amplifier(basically L-pad resistor), simple configuration: Amplifier => attenuation ...
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2answers
151 views

Is my understanding correct in selecting ADC resolution? (Noise analysis)

I have posted a similar question before: ADC resolution, considering DSP. And finally I think I know the answer. Could you please have a check on it? Here is the set up: The input signal of the ...
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2answers
92 views

Determining Bandwidth of any circuit

I am getting familiar to SNR, noise calculations, thanks to this forum, however I often come across Bandwidth of the system to calculate resistor noise, to get rms noise from nV/rt-Hz, etc. I have a ...
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2answers
151 views

How to separate two DC voltages in a dual power supply?

I have a dual power supply (Lacie ACLG-51) that supplies both 12V DC and 5V DC with a common neutral (3 wires) I have used it to drive a little system composed of a Raspberry Pi (5V), USB HUB (5V), ...
3
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1answer
252 views

Understanding source and return current flow on PCBs

I'm looking for advice and tips related to PCB board layout and signal+ground trace/track routing. I'm designing a 2-layer analog-only PCB that has several I/O signals leading to and from other ...
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2answers
96 views

Noise cancellation for electromagnetic signals

I am working in the oil field with tools which I need to connect by cables (which "should be shielded") to computers. Most of the time when I communicate with my tools, I face grounding issues. I ...
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131 views

Low-pass filtering a 120 volt AC line to remove noise

I have active monitors (speakers) plugged into a 120 V line and they are picking up 120 Hz noise being generated by the TRIACs of the Lutron light dimmers in my house. The dimmers are on different ...
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2answers
753 views

How to route with minimum noise

I'm facing a dilemma on how to route correctly in order to minimize noise on a data signal line. In the example bellow there is a 2-layer flexible PCB (which is very thin). The copper layer is 1OZ and ...