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

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21 views

WiFi signal coupling to my amplifier

I have a board with a sensitive analog amplifier. This amplifier is optical in nature and it has a gain of 6M times. On the same board there is a Wifi module. Somehow when Wifi is transmitting I see ...
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2answers
47 views

Relay causes USB sound card to freeze

I am using a relay to control a 230 VDC duct fan. Sometimes when the relay turns off my USB sound card freezes, to get it back I have to toggle the power (pull the USB cable, as it is USB bus ...
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1answer
1k views

What's with all this noise?

People often talk about noise in circuits. Cheap op-amps are noisy, running a motor can create noise on the supply, and a lot of analog circuits deal with the signal-to-noise ratio (ie: trying to keep ...
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1answer
61 views

high speed optocoupler circuit

I have 4n35 optocouplers, I am using these to isolate a motor driver circuit and the Arduino controlling it. I put one on the slave select pin and one on the tx line to the motor controller (there is ...
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2answers
182 views

Electrical noise on guitar pickups from computer. Due to radio interference, or inductive coupling?

When I point my guitar pickups towards my desktop computer from several feet (2 1/2 - 3) away, I can hear a lot of buzzing/clicking, depending on what the computer is doing (idling vs, say, playing ...
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2answers
322 views

Physically, how does connecting a PCB to chassis ground reduce noise?

I realize this may seem to duplicate Should chassis ground be attached to digital ground? but the answers in that thread don't explain why one should connect the chassis to PCB ground, aside from ...
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4answers
344 views

How to fix EMC problems for existing designs?

I'm going to be looking at a few products that have failed EMC radiated emissions testing and will need to apply fixes in order to make them pass (unfortunately, in these cases, two of the designs ...
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0answers
32 views

How do I draw M-PAM curves of Channel Capacity Vs SNR?

I've seen the following figure in several different articles: (this one was taken from here) I understand that channel capacity of the Gaussian signal is ...
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33 views

Modified Sine Wave Inverter to power MPPT circuit/microcontroller and Laptop?

I am going into uncharted territory for my senior design project. I need to build an MPPT circuit to efficiently charge a 55AH or 75AH battery. The design because of my lack of programming expertise ...
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2answers
86 views

Ground Loop? Noise from 12v to 5v converter manifest in bluetooth audio source

I've created a custom, bluetooth audio harness for my Jeep WJ using off the shelf parts. Amp - Clarion XC1410 Converter - 12v to 5v buck converter Bluetooth Audio - Logitech Wireless Speaker Adapter ...
3
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1answer
55 views

Power supply noise measurements

Im working on a project where I need characterise the noise from a power supply so I can then design some filters. The power supply provides 5V, 12V and -12V to a set of analogue sensors (hence the ...
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3answers
54 views

How to convert noise to noise density in mic pre amps

I am trying to compare two low noise mic pres for the lowest noise, and I am looking at the TI1012 and MAX9814 MAX9814: ♦ Low Input-Referred Noise Density of 30nV/√Hz TI1012: Output Voltage Noise ...
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1answer
46 views

Filtering Noise on Strain Gauge Circuit

I am making a digital weighing scale circuit and currently having difficulties understanding filters that are commonly used to reduce noise in these type of circuits. My load cell is a full-bridge ...
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3answers
138 views

How differential amplifiers help reduce noise?

First off, I'm new to electronics. Can anyone please explain how differential input reduces noise? My understanding (please correct me if I'm wrong): noise usually gets added to the original signal ...
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2answers
61 views

Noise on power line when charging USB

For the starter: I have build device that use DTMF code to control LED light the device can be both power from USB charger or integrated on the board PoE module. The power is also used to power ...
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2answers
76 views

How does water damages the phone lines?

Today, we just replaced the phone line which was damaged due to moisture and were causing a great deal of disturbance and noise in the phone. What exactly causes this noise? Does the signals gets ...
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0answers
53 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
82 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
77 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
168 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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0answers
45 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
140 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
70 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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0answers
46 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
71 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 ...
0
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1answer
69 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
49 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
80 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 ...
2
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2answers
84 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
81 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
254 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
66 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
92 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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0answers
36 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
59 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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0answers
55 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 ...
0
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1answer
188 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. ...
3
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1answer
210 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
77 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
45 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 ...
0
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1answer
69 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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0answers
35 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 ...
3
votes
2answers
202 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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0answers
82 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 ...
2
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1answer
140 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
128 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 ...
0
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2answers
117 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
33 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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98 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
179 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 ...