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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EMC tests requirements

I have designed many boards since graduation in my position as Hardware Engineer, but none of these boards tested its electromagnetic compatibility with the standards. However in all my designs I have ...
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How can I use an inductor as an EMI sensor?

In the paper "Synthetic Sensors: Towards General-Purpose Sensing" by Gierad Laput, et. al, they use a 100 mH inductor as an EMI (electromagnetic interference) sensor. They have not provided ...
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Are Solid State Relays Noisy - EMC?

I have a question regarding SSRs. I am working on redesigning a PCB for a medical device that needs to pass class B radiated emissions, therefore radiated EMI must be very low. We have a CPU fan ...
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Why are engine spark plugs w/o resistor so potent killers of electronics nearby them?

I've recreated the ignition coil part of a small Honda ICE (typically used in lawn mowers or single-digit kW gensets). I use an electric motor to turn a flywheel taken from a dead engine, and I've ...
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Powering ESP32 LDO or Buck converter

im designing an ESP32 system with three haptic drivers. Description of the system: 3 Drivers: 3.3 V 15 mA ESP32-pico-D4: 3.3V Sleep mode: 50 mA Active mode: 150-300 mA Antenna: Compact Reach XtendTM ...
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37 views

EMC test for device with WiFi module

I want to test EMI radiated for a medical device with a WiFi module. This medical device connects to a tablet to perform its function. In the EMC chamber we have a lan and a USB connection outside ...
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Advice on Bulk Current Injection Testing

I am having trouble getting a new product I'm working on to pass Bulk Current Injection Testing. I had trouble on the 50mA test at around 30MHz where the Ethernet link was not functional. I have a 6 ...
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Wireless internet signal bi-directional amplification?

So I have little to nothing experience with anything wireless related. the WiFi modem I have in my house is far from my room and the signal is weak, so it reduces the communication rate. my first ...
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Why do some PCBs have exposed copper along the edge even when mounted in plastic enclosure? [closed]

I've already read about reasons for exposing copper at the perimeter of a PCB (i.e. Why do some PCBs have exposed plated perimeters?). It seems that the main reason to completely expose the copper ...
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A typical GPIO works at 150MHz without risk for EMI but why is there a risk of EMI at even 400KHz in I2C?

In I2C the fall time is restricted to around 20ns as a risk of EMI(Even at 400Khz) but even a normal GPIO works at 150 MHz.Why is this so?
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Why did the designer of this flyback circuit choose to set the oscillation frequency as high as possible with the smallest resistor tolerated?

This circuit uses a current mode controller with an oscillation frequency response of: In the circuit, the designer chose to use a 10nF cap, with a 680 ohm timing resistor, which according to the ...
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Do I need to suppress ringing in a flyback converter?

I am about to design a flyback converter. As all flybacks with no extra measures it has some ringing. You can see that ringing in this example from -1µs to 4µs: This ringing can be surpressed by a ...
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Why are radiated emissions standards for consumer electronics different from industrial?

Why are radiated emissions standards for consumer electronics different from industrial? Source:??
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Why isn't capacitive coupling considered in EMC testing?

It seems like the emissions of interest in EMC testing are radiated and conducted emissions. Is this because capacitive coupling is so weak it doesn't pose a threat to other devices?
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High voltage contactor EMC circuit

I am using a 12V relay to drive high voltage contactors. The contactor coil causes EMC when turned off. I am uncertain of which circuit I should use for reducing the EMC. Is there even any difference ...
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Protection and termination of an outdoor underground Ethernet cable

I have quite a quite long outdoor FTP Cat 5e Ethernet cable (just shorter than 90 meters) that will be used to connect 2 buildings, buried 1 meter underground. As I understand, for a proper operation ...
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51 views

Isolated DC-DC coupling capacitor location?

For a coupling capacitor across the isolation barrier of a DC-DC converter to provide a return path due to the parasitic capacitance in the transformer, there seems to be many different configuration ...
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DC-DC converter isolation capacitance return path?

For those isolated DC-DC converter bricks like seen in the photo below: The data sheet specifies an isolation capacitance in the order of picofarads. And in order to meet EMC requirements they ...
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69 views

Controlling a Brushed Motor with DC Voltage to Avoid EMI (no speed control needed)

I have a fairly simple project coming up. My task is to design a system which powers and controls a Pan and Tilt positioner for a camera. It has some weird and unavoidable requirements/constraints: ...
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Automotive filter against voltage spikes

I am building a electric vehicle relay controller. Which controls the High voltage relays among other things. I have built an automotive power supply circuit with strong inspiration from this article: ...
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Is EMI/EMC still a big concern for a PC case?

I've recently started looking into researching potential concerns when it comes to using a non-metal material for a custom PC case, specifically wood. I've seen people talk about heat, electrical ...
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Electro magnetic interferences (EMI) generated by power circuit reset low voltage integrated circuits (ICs)

The main question here is (explanation will follow): Is there a way to filter out low voltage oscillations (>10MHz) on pins that have to stay high for the system to function? Oscillations are ...
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What are some quick, cheap hacks for determining the source of EMI in my house?

TL;DR - Without dumping a bunch of money, is there a quick MacGuyver-y way to help diagnose what's causing the EMI in my house? Longer - I have the curse that I'm a little too technical to be helped ...
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how does it improve EFT immunity

how does this design really improve EFT immunity. where does EFT come from i guess (VDD) as spike ? in my estimation i would say (10k+100nF) is more robust from changes on VDD? in fact the 100pF is ...
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Design of bias-T (L band,10 MHz,DC)

I want to design a bias-T for satellite application where L band RF (950-2150 MHz),10 MHz, and DC will be multiplexed. I need help in finalizing/selecting the inductor(choke) through which DC (13V/18V,...
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How to identify or calculate the electromagnetic interference (EMI) contribution of components on PCB

I am designing a circuit using the Motor Driver IC TB6612FNG. Now I am unaware about how can I calculate the EMI contribution by this IC. I did add the bypass and decoupling, grounding control, ...
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Placement of damping resistors, closer to driver or load?

I'm connecting an FPGA and MCU and currently optimizing the placement. Does it matter if it's randomly placed? Should I place it like a series terminating resistor and strictly place it close to the ...
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I/O panel filtering for shielded room

We are looking into setting up a very basic shielded chamber inside a small room at my company to be able to perform some basic relative radiated EMC measurements. We will buy a somewhat cheap ...
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Relation of sweep time and number of measurement points in Spectrum Analyzer

My configuration is as follows: RBW: 100 kHz Detector: MAXPEAK Frequency span: 1.1 GHz - 1.8 GHz Spectrum Analyzer: R&S FSV 30 I do not fully understand how the sweep time and number of points ...
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57 views

Atmega MCU freezes when nearby VSD starts. Possible causes and solutions

I have a custom PCB that uses an ATMEGA1280 MCU. The board has a few inputs and a relay output. Inputs are mostly 4-20mA measuring temperature sensors. I also measure VSD current from a VSD mounted ...
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Should I avoid a switching frequency close to my target SPI or CAN frequency?

I have a kind of an open-ended question. If I'm designing a board with a buck converter and have picked out my peripherals, and say for example I want to run my CAN FD interface at 1MHz baud and maybe ...
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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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Quartz Crystal with or without metal lid for EMI suppression?

Is there any reason for choosing a quartz crystal with or without metal lid? Some datasheets (this one for instance: link) claim better EMI performance and other do not write at all about it. So is ...
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Mesh Wire opening size for emi filter at frequency of 30Mhz

I want to use a mesh wire and I wanted to know how do I calculate an opening size of a mesh wire that can filter 30Mhz frequency. Your help is appreciated.
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Connecting USB shield to system ground [duplicate]

I designed a PCB with an STM32 and a micro USB connector. I put a NUF2042XV6T1G between the connector and the STM32 to protect the data lines. The USB shield is connected to system ground via a 120R@...
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CAN - Tranceiver @ 5V VS Tranceiver @ 3V3 Immunity

I would like to change a 5V CAN transceiver on my board into a 3V3 CAN transceiver. Nevertheless as I am clearly not a specialist of the CAN protocol, I am afraid of doing a big mistake ! I think it ...
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126 views

Universal Relay Snubber Circuit

I am trying to design the usual remote-controlled relay board for mains usage (I live in Europe, so that means 230VAC). I need to tackle the usual problem of the switching of the relays hanging/...
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1answer
66 views

Ground vias use on no-trace areas at a 4-layer PCB

Background info: I am using a 4 layer PCB stack: Signal, Gnd, Signal+Power, Signal (mostly ground). To avoid out of question issues, I use this set-up due to a reference design on Texas Instruments as ...
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What is this spongy material?

Hi, while I am tring to repair electronic circuit. I'm encountering this sponge. I wonder what is this sponge? and can I find out what it is used for. I often see this in sensitive circuits like in ...
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Is EMC (FCC and EU) testing performed as sold or as used?

I have a prototype that inserts a fairly weak ISM band RF signal (HF/VHF) as a way of detecting a connection between two metal objects without there being a DC return path (Ideally I would use TDR but ...
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5V tolerant - tolerant to 5V and how many more ? Harsh environnement

There is a lot of questions about this subject... Nevertheless this is not clear to me and clearly I m afraid of putting a signal at the input of a microcontroller which is higher than this supply ...
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Inverter EMI filter design

I'm designing an inverter with a switching frequency range of 10-40kHz. The inverter will run off of a DC power supply at a relatively low voltage (30-80VDC) and low power (~100W) for motor control ...
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Reduce 50 Hz noise from robot-mower charger

I just bought a robot-lawnmower (Husqvarna Automower 105), which is working perfectly. But the charging station is making a loud 50 Hz noise all the time, even without the robot charging. I have ...
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Why are high frequency signals not disturbed by stray fields?

I am trying to design an inductive position sensor based on a high-frequency signal. It is mentioned that using high-frequency signals gives immunity towards stray magnetic fields. Could anyone ...
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50 views

Conducted Emissions of EV Charging Electronics

I'm building an AC-charging device for electric vehicles (the standard calls it an "ICCPD" or an "In Cable Control and Protective Device") and I'm facing some EMC issues due to the PWM Signal on the ...
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Generating 5V from 37V DC with no EMI

I'm making a PCB for an audio amplifier + power supply (circuit here). The power supply voltage rails with my transformer end up being about +/- 37V, and I want to generate a 5V rail from this for ...
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What kind of inductor for DC-DC converter module's EMC filter?

I'm looking at the datasheets for a number of switching DC-DC converters. They suggest for EMC filtering to add an inductor and a capacitor or two on the input side of the converter. The question: ...
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LTspice model of the UC3845 oscillator

I have a circuit whose the purpose is to reduce the EMI by "moving" the switching frequency around a value. I would like to understand how this circuit affects the switching frequency, i.e. how it ...
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Where does Differential noise come from in a switching power supply

I would like to know where does differential noise come from in an SMPS. I understand where the common mode noise comes from. It mainly comes from the fact that there is capacitance between switching ...
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Line Impedance Stabilization Network (LISN) ripple to measurement transfer function

While reading about LISNs, I was lost a bit. The CISPR limits are in dBμV, so they're voltages. But are these an image of the current following IN the DUT? Below you're see the LISN transfer ...

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