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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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36 views

EMC testing of devices with Ethernet

I've made a board with two Ethernet ports on it and so far when testing it for EMC I've been connecting them together with a single cable. My assumption was that since there are constant keepalive ...
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29 views

Does a load reactor eliminate the need for EMC cabling?

The company I work with installs ventilators driven by VFD's. To save on cost of EMC cabling we use load reactors at the VFD outputs. (Other considerations for not using EMC cabling have to do with ...
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166 views

How can I fix EMC problem over my PCB?

Here is my PCB drawing that couldn't fix EMC problem. There are peaks at 120-130 MHz at radiated measurement. Are there anyone who have any opinion to fix this? Note: My circuit behave as led driver ...
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Hobby breadboard wiring guidelines to stay within legal RF/EMI limits?

Assume a middle school or home hobby lab with a bunch of breadboards, jumper wires, and 3.3V microcontrollers fast enough to toggle IO at RF frequencies (if not at the fundamental, at lower harmonics ...
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43 views

USB Charger Voltage Specification - Transients

Is there a specification for a USB charger that discusses whether voltage transients are acceptable, is if so, under what conditions? Specifically, I know a USB charger needs to have a voltage of 5V +...
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48 views

Electroluminescent wire and EMC

I have been thinking about using EL wire in our house as a night light but I am concerned about electromagnetic compatibility and possible adverse effects on the inhabitants (we). You can see these ...
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1answer
39 views

Decoupling capacitors on opposite side of board when using PCB mount EMI shield

When using a PCB mount EMI shield, can you put decoupling capacitors on the back side of the board? Well of course you can put them there, but will it make the shield essentially useless? Or will ...
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77 views

Caseless PC - should I be concerned about incoming EMI

This is a follow-up to this question. I have built a custom PC case that is essentially cardboard. Are the components likely immune to ambient EMI or do they build them under the assumption that a ...
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33 views

Syfer (now Knowe) X2Y EMI filter

I struggled to compare the EMI filter needed for 24V to 5V non-isolated BUCK DC/DC (running 300KHz to 500KHz) to ensure it passes CE conformance. I wish to keep switching noise within the DC/DC area ...
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144 views

How to design this filter?

I've a full bridge dc-dc converter and I'm trying to understand it. It has 48V input and 400V output with 1600W rating, 30kHz switching frequency. At the input of this SMPS there's a filter ...
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58 views

RS485 - Comunication lost during EFT IEC 61000-4-4

I'm having throubles with communication over RS485 in harsh industrial environment. We perform test in EMC lab, acording IEC 61000-4-4 = Fast transient (also known as Burst). We used burst generator ...
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109 views

How can I easiest (cheapest) I'm within EMC regulations?

I'm a hobbyist that's currently developing a simple clock and hoping to make it into a small scale sellable product. It's a simple 5V USB clock with a ATTiny84 8MHz clock, a RTC-module and some WS2813 ...
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52 views

Very long PCB trace causing microcontroller to wakeup?

I have a design where I'm using an ESP32 as the device's main controller. The system is battery powered, so the ESP is in deep-sleep a lot. It can be woken up with a simple button push (detecting for ...
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52 views

Radio static caused by windscreen wipers

I was driving past a radio station transmitter of the radio station I was listening to. I turned on my windscreen wipers, which caused a noticeable static to be emitted through the speakers for the ...
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60 views

Experimenting with a Walkie Talkie

This is one weird bizarre thing which I noticed while I was in the electronics lab. I had this Power Supply and a walkie talkie similar to this I have not ventured in RF side yet. The power supply ...
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33 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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120 views

Is EMC shielding of a grounding wire required?

Consider the following 2 use cases: Fully electric vehicle with 2 different insulated voltage systems: 1 high voltage @1000V DC insulated from chassis and 24VDC system with minus pole (-) at chassis. ...
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49 views

Low Frequency EMI

I was wondering if low frequency EMI can occur with PWM or other sub MHz signals. I am aware that harmonics of these signals can generate EMI but I was wondering if the fundamental frequency can ...
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39 views

Emi Filter Design with Tracopower isolated power supply in railway application

I'm designing, for a railways application, the power supply circuit on a pcb board that supply 5Vdc starting from a 24Vdc(coming from a not clearly defined source, sure a 24Vdc line). I'm using the ...
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44 views

EMC issue on isolator part

I have used two X1 safety capacitors in series with an isolator (ISOW7842DWE). I have fault on EMC test on 64MHz. When I remove the capacitors, the EMC issue is reduced by 6dB. I have used two safety ...
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41 views

RF output power too high because of PSU cable

We have a situation where an integrated 868-920MHz RF chip is programmed to output the chip maximum of 14 dBm power. From professional chamber/measurement equipment 16 dBm is measured in the carrier ...
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42 views

Voltage spikes caused by stray wire

I recently had a PCB designed which has several analog, digital, and power elements. The board is powered by 24Vdc which is stepped down using an LDO to 3.3V and 5V. These voltages are used to power ...
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93 views

EMC issue on 6 layer PCB design [closed]

I have EMC issue and there is spike at 64 MHz on my 6 layer PCB design. I have used many decoupling capacitors and ferrite beads according to the datasheet. Is there any cad tool to measure on which ...
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44 views

Proximity of a DC / DC converter and operational amplifier

There is an operational amplifier LM258WYDT, which outputs a signal with a frequency of 1 kHz. It is powered by an TMR1222 isolated DC/DC converter, which produces +12/-12V. For example, the DC/DC ...
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What could potentially affect some specific LoRa frequencies among others and how to mitigate it?

I have started a small LoRaWAN network. I already have setup: 1x LoRaWAN gateway (LAIRD RG186, using EU863-870); 4x T/RH Nodes (Dragino LHT65, same standard); LoRa ...
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57 views

Relay Switching MCU Hanging/Reset

I am working on samD21 MCU to control the 16 relays. I am also using a circuit to detect the input AC switch status On/OFF (Connected serially to the relays). This is connected through optocoupler ...
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56 views

DC brush motor EMI

What kind of frequency does a DC brush motor generate? There are a few explanations online as to what causes EMI in DC brush motors (commutator sparking for example) and how to reduce it, but no ...
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32 views

EMI Filter - DC DC Converter No Differential Mode Filter Outlined

I am currently looking at installing a DC-DC Converter. https://www.xppower.com/Portals/0/pdfs/SF_QSB300.pdf The datasheet outlines a recommended EMI filter as so: My question is as the datasheet ...
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53 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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2answers
116 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 the ...
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1answer
59 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
66 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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39 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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72 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
115 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
99 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
116 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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24 views

Power Transformer Electrostatic Shielding effectiveness

Most power transformers can benefit from an electrostatic shield between Primary and secondary if there are EMC issues .Even if the transformer is 50/60Hz powerline interference can be supressed. ...
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1answer
27 views

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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2answers
84 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
79 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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0answers
132 views

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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2answers
146 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
37 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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3answers
121 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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528 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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1k views

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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37 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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2answers
92 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
74 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 ...