Questions tagged [emc]

Electromagnetic compatibility (EMC) is a branch of electronics related to identifying and solving problems caused by electromagnetic interference (EMI) between devices. It encompasses both attempting to prevent unwanted emissions from a device and also ensuring that emissions from another device will not cause spurious operation.

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56 views

Current induced on a transmisison line

I have a micro-strip transmission line as shown in the figure which is incident by an external EM field. This field will induce some voltage and current on it. I want to measure the induced voltage ...
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360 views

The Pin 1 Problem in Audio, Star and Mesh Ground, and Contradictory Grouding Practices in Audio and Digital Systems

I recently came across the concept of "Pin 1 Problem" known in the pro-audio electronics. It seems straightforward at first, but becomes confusing when it comes to grounding. Let me describe ...
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62 views

Abnormal microcontroller circuit behavior when I connect SMPS

I designed a device that calculates current and power using a CT and an ATMega328P-AU microcontroller. The board I designed was simple and I didn't account for noise cancellation on the ADC lines and ...
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1answer
160 views

230VAC line voltage sensing using MCU pin

I Am designing a circuit to detect the presence of AC line voltage.It is basically to detect the switch On/OFF for a load. Here is the circuit. Here Input resistor ladder to step down the voltage. ...
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62 views

Snubber capacitor Voltage rating

I am designing a switching circuit for celing fan (max 80W/230VAC). This is basically relay based switching. I planned to add snubber circuit to reduce the back emf. I got a resistor value of 100&...
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78 views

Determining motor position with EMI

I would like to determine the position of a motor based on its radio emissions, I do not have access to said motor but I am trying to reverse engineer it. Here is what I know about it : It has X ...
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2answers
145 views

Is shielding the entire circuit with a faraday cage a good idea?

Let's suppose I have a circuit which contains a 3.3V MCU and a buck converter (let's think that its frequency is higher than 400 kHz). I'm wondering if shielding the entire circuit would not a good ...
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1answer
176 views

Are input filters always required for switching power supplies?

This is a follow up to the questions here and here I recently designed a PCB that contained a buck regulator (LM2576 5V). You can see the PCB layout in this question. After converting the input 12VDC ...
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1answer
143 views

How can I generate a noisy environment to test my PCB?

I am developing a PCB project but i want to use the PCB in noisy environments (which usually contains 7.5-45 kW multiple motors with frequency inverters and also ignition transformers). I made some ...
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Recommendation ITU-R BT.1729 test image for 5:4 display

For radiated emissions testing according to EN 55032 CISPR 32 with displays of category 4, there is a Recommendation ITU-R BT.1729 which specifies a reference test pattern. The pattern is designed for ...
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188 views

Shielding and Ground Loops - RF panel jacks for GPS

I've been working on a design that requires me to pass an RF signal through a conductive panel. I'm using SMA jacks for that purpose as they're readily available and also available in an isolated ...
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1answer
136 views

Reducing EMC from a long trace where one end is normally floating

Following on from this question about a PCB layout with EMC issues, I'm currently reworking the design to minimise breaks in the ground plane and try and identify any other EMC issues. One thing that ...
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GSM noise from a 2-layer PCB with SIM800C

I've designed a 2-layer PCB that contains a 12-5V buck converter (P2576L-50 - a Clone of the LM2576), 3.3 (AP1117-33) and 4V (MIC29302WU) shunt regulators, an STM32 micro and a SIM800C GSM module. ...
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220 views

Is it okay to join two ethernet cables by soldering?

I want to connect two Ethernet (UTP) cables. Both of them have connectors only on one side. Is it okay to solder the wires together? Could it affect maximum speed? (For example I wouldn't be able to ...
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1answer
44 views

How to reduce EM radiated emissions in a 2 layer board with 2 components?

Consider a 2 layer PCB with Layer 1 is a signal layer (the traces in this layer are indicated with black arrows in the picture below) Layer 2 is a ground plane, also called GND in the following (the ...
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157 views

Can we connect Earth , Neutral and Digital Ground together in electronics system?

In our project has Digital Ground , Earth and Neutral. As per the requirement Digital Ground and Earth ground tied through Bead inductor. Is it advisable to connect Neutral with Chassis and Digital ...
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620 views

In a 2 layer PCB with a top layer densely populated, from an EMI & EMC point of view should the ground plane be on top, bottom or both and why?

Suppose I have a 2 layer PCB with the following characteristics: Top layer is relatively densely populated by both THT ad SMD components Bottom layer has very few traces Among the following, what is ...
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Why do oscilloscopes use SMPSes instead of linear power supplies?

I'm wondering why digital oscilloscopes are using switching power supplies instead of linear power supplies. The SMPS has a higher efficiency, but it can produce some noise during high frequency ...
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58 views

Connecting TVS diodes to a floating shield

I need a little help with shielding for ECG leads. The design I'm working on has 3 leads, about 60mm in length. We use shielded cable for each lead, which all come to a meeting point at the ...
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150 views

FCC certified module with uncertified antenna: technical or legal issue?

Say I have a consumer device that uses a pre-certified WiFi module. As I understand it, radio modules are certified with a fixed set of antenna choices that were included as part of the module's ...
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3answers
86 views

EFT Design training

My team is responsible for designing industrial electrical devices. We had successfully designed several devices before. Recently, we are designing products that have to meet IEC 61000-4-4 class A ...
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1answer
485 views

Filtering power to stepper motor drivers for EMI

I have been using Allegro A5977 stepper drivers for a while now (a few years) and I had not too bad of a result meeting the EMI compliance targets even for CLASS B. However I went by the seat of my ...
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34 views

ECG for fluorescent lamp and grounding

I have three OSRAM Quicktronic DIM T8 1x 18W in the same room. One is near the wall outlet, the other two are each about 10 m away. Each one is very close to the respective T8 tube. While the first ...
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Why do some PCBs have exposed plated perimeters?

I've seen a number of PCBs, largely high speed and RF boards, that have exposed copper, either at the perimeter of the entire board, or in various sections, often with stitching vias. I've never ...
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127 views

Proper Way to PWM (Voltage Control) Dim LED Strip

I have been asked to create a dimming system (Along with other features) that interfaces to the cheap LED strip lights. A lot of people seem to use standard N-FETs with PWM on the low side. My concern ...
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54 views

How to measure noise on an antenna in system

I am working on an antenna based RF receiver (AM/FM radio) that appears to be picking up interference from other parts of the circuit. I want to view the noise spectrum, but the receiver chip doesn't ...
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1answer
71 views

Where to place RF shield

I'd like to put a pump drive circuit similar to the one shown below on the same PCB that has two I2C devices, a GPS module, seven analog signals, an ESP32 MCU transmitting WiFi via a trace antenna, ...
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130 views

Pulses counting problem from npn proximity with interrupts in arduino

I am interfacing an open output npn proximity sensor with Arduino nano. I have used very silly approach of voltage divider as I was not sure that in open output sensor you can get whatever voltage you ...
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1answer
68 views

Reading analogue sensors in a noisy environment

I need to read the values from several analogue sensors mounted on a circuit breaker in an electrical substation. I'm not working with any high voltages, but the circuit must still work as the breaker ...
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2answers
65 views

Shielding to Block Wi-Fi for Testing No Signal

I was trying to conduct a test recently to show that the system I am developing behaved as expected when it can't connect to the Wi-Fi network it is configured for, and then subsequently to test that ...
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2answers
59 views

Question on basics of EMC

In power electronics supplies when a common mode choke is used at the supply or before a converter (say a synchronous rectifier) , does it mean the choke is used to avoid common noise coming from the ...
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71 views

AC EMI filter specification

I am looking at the specifications of an EMI filter for single a phase ac application, and I noted that the datasheet specifies an operating frequency from DC-400Hz? Do you have any idea of what this ...
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127 views

what if the two wires of a single twisted pair are different in length?

For example, one wire of a twisted pair is longer than the other wire (imbalance starts from the middle of the twisted pair, everything is balanced before the middle point). What problems will it ...
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140 views

EMI filtering on multi-FFC assembly

an aspiring electronics engineer here. I do some electronics design for work and I'd like to know the following: If I have an assembly of a main board, to which an FFC cable connects into a second ...
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1answer
27 views

Small switching regulator EMI

Well, it's taken me weeks to think of a new absurd question but here I am at last. You're welcome! I'm looking at using a small, adjustable, switching buck regulator (likely a LM2574) for a very ...
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4answers
136 views

Electromagnetic Interference in Cable

I am currently building a cable and would like to possible reduce any EMI. Three signals ( GROUND, ANALOG SIGNAL AND VCC) are connected to the encoder. I plan on twisting the Ground and VCC to cancel ...
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2answers
116 views

How damaging can a leaky microwave oven be?

This question is mainly about EMC and disruptive RF emissions. I have noticed recently that each time we use our microwave oven the WiFi network becomes unusably slow (it is still working if you get ...
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1answer
85 views

signal propagates in bending transmission line (unequal length between signal path and return path)

Suppose I have a square wave signal generated from a signal generator and its outputs are connected to the two terminals of a paired PCB traces (left side of the picture below). The other end of the ...
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3answers
1k views

Why does PWM create lots of EMI and signal ground noise?

TI had a note to create DAC signals using PWM. http://www.ti.com/lit/ug/tidu027/tidu027.pdf Whereas I also found an article that says http://www.mosaic-industries.com/embedded-systems/...
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71 views

RFI protection for a stepper motor controller

I'm building a remote tuning device for a magnetic loop antenna. It will use a stepper motor to turn the shaft on the mag loop's variable capacitor. The electronics will consist primarily of a ...
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35 views

Noise testing method

I have Electronic board with power supply , control board etc. I wanted to conduct noise test . Is there any standard procedure available. I wanted to check if i induce the noise into power line or ...
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1answer
135 views

VCC on surface or inner layer on 4-layer board?

If I can get away with, I will use 6-layer design where I get two dedicated GND planes, L2 and L5, which creates strong reference plane for traces on L1, L3 and L6. When you're working with 4 layers,...
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270 views

Why are “devices utilized exclusively in any transportation vehicle” exempted from FCC compliance testing?

I was researching whether do we need to do FCC compliance testing for a device we developed for a client. Curiously, it seems to be in the list of exemptions (passage taken from here): A digital ...
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3answers
97 views

If a PEC surface completely reflects an EM wave, why doesn't an ungrounded shield work?

I was thinking about shielding and its effectiveness. An ungrounded shield doesn't work well for either inductive or capacitive coupling. However, if you think about plane wave theory, a PEC surface ...
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137 views

Viable alternative for expensive MLCC capacitor?

I'm thinking of building and selling a product which uses a DC-DC isolator. I've been prototyping with Recom RI3 3W Isolated DC-DC Converter Through Hole, Vin 5 V dc, Vout 9V dc, I/O isolation 1kV. ...
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1answer
380 views

Overloading of ESD protection diode on CAN lines through current during Bulk current injection - test

I have a design checklist question for a typical CAN circuit for an automotive application as below : The question is related to the ESD suppressor : "Was a capacitor parallel to the diode considered, ...
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131 views

Placement of RC filter used for slew rate limiting (for EMC)

I've seen RC combinations used on many circuits now which i believe have been included for slew rate limiting. They usually feed off to a connector. Do the placement of these matter in the circuit? ...
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2answers
143 views

Which areas do I remove copper pour to reduce noise?

I have a 2 layer PCB that carries a microcontroller (Particle Electron), connects to a sensor with an ADC reading, has an ADC comparator IC, a watchdog timer IC, a PNP switch, an power bus and I2C ...
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167 views

How protect analog input connected to thermistor through long wires

I'm developing a data acquisition board for 8 thermistors hooked up through 3 feet wires. The board is gonna be installed inside a package unit air conditioning. In there, we have compressors, fan ...
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1answer
53 views

Inductance value of PI-filter connectors?

I find myself in the situation of being forced to use filter connectors to solve an EMC issue very late in the project. Normally, this should of course be solved in circuit design, but as projects and ...

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