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.

123 questions with no upvoted or accepted answers
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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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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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1answer
134 views

Sequencing modes for FCC “Intentional Radiator” test

I'm FCC certifying as an "intentional radiator" a product that uses a custom antenna and off the shelf Broadcom WiFi module. The module has an antenna port, so single-modular and limited single-...
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33 views

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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238 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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131 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
54 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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397 views

Flyback Transformer - Grounding the Ferrite Core

Today I dismantled (I hope this is the correct verb) a flyback transformer. The thing that I've never seen is that one end of one of the windings is "glued" to the ferrite core (Before you ask; yes, ...
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2answers
289 views

ESD/EMI Design for CE, Recommendation seems wrong from test lab

I have designed a product for a customer, that now needs to pass UL/FCC/CE Testing, It passed UL & FCC but failed CE for both 8kv ESD and EMI. The Chinese test lab my client went through sent me ...
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1answer
67 views

What are the relations between analog transmission frequency and multipair cable types?

My question is a little theoretical about multipair cables. I want to have some basic understanding about the relation between the multipair cable types and application frequency, length and and EMI ...
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893 views

Differerent connection for Y-capacitor (EMI filter)

What is the difference between these two connections Y-capacitor (EMI filter)? *high-voltage side to isolated 12V DC output *isolated 0V DC output rail and a "GND" Could you tell me the raison of each ...
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516 views

EMC Filtering for BuckBoost LED driver

I'm designing a Buck boost LED driver using the ZXLD1370 IC. the circuit works but as one engineer said ("its easy to design a circuit but difficult to get it to pass EMC). This is where my problem is....
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195 views

How does this diode improve the common mode conducted noise?

This image was taken from UCC28881 (page 16) The desciption in the body says: A half-wave rectifier is chosen and implemented by diode D2 (1N4937). It is a general purpose 1-A, 600-V rated diode....
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317 views

Deliberate Shoot-Through in H-bridge for EMI reduction

today I was analysing an H-bridge driver circuit in a commercial product which is used to drive a DC motor (approx 24V/4A) over an unshielded cable with about 1.5m length. When I did a simulation of ...
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5k views

Shielding effectiveness calculation

From The Basic Principles of Shielding: Apertures, or holes, have SE. The SE of an aperture and ultimately the entire electronic enclosure is determined by the size, shape and number of the apertures....
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42 views

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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30 views

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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26 views

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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44 views

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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53 views

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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2answers
66 views

Electromagnetic compatibility problem with an hairdryer

I wanted to ask you if you could give me an explanation of this electromagnetic compatibility problem. I connected my (fully working) TV to a certain electrical socket in my house. I have also a ...
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21 views

Questions about grounding schemes when converting a double-insulated audio amplifier into a power supply for a 90vdc treadmill motor

I was given a free Denon AVR3311 AV receiver (a.k.a. audio amplifier) which I immediately gutted and converted to a bench power supply. I combined the "B+" and "B-" rails into a single, ~130Vdc output,...
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60 views

Need to branch USB data lines… what to do with unused ends?

I have a USB 2.0 low-speed connection design with an unusual constraint. On the host side the D+ and D- lines have a branch, a requirement of the connector and this cannot be changed. On the device ...
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1answer
57 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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49 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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1answer
45 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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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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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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142 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
382 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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1answer
440 views

Use of internal PCB ground plane as ESD baseplate/EMC reference plane of product in plastic enclosure

I am designing an electronic product which will be housed in a plastic (non-conductive) enclosure. There are a number of, mostly shielded, I/O cables (Copper 10/100/1000Mb/s Ethernet, USB 2.0, RS232, ...
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73 views

Electro magnetic interference with Arduino Uno and a portable radio

I'm surprised when I'm working with Arduino Uno, by just sitting beside a portable radio, like when I was powered on both Arduino & Radio and when they are close to each other I got some noise ...
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531 views

In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV?

In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV? Cause of reason: The reason for this is that I've a modeled a LISN in LTspice where I want to simulate ...
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2answers
174 views

What's the current leak path of the electrostatic discharge during an EMC test?

When we develop a new product we need to pass the EMC test,I really wonder what's the current path during a electrostatic discharge test. Here is the test situation: Q1: If the EUT(equipment under ...
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1answer
378 views

EMI/Y-capacitor in inverter phase outputs?

Is it good or even used practice to filter out common-mode EMI in 3-phase industrial inverter (IGBT) phase outputs using phase-to-earth Y-capacitors? High du/dt might limit the lifetime of such ...
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114 views

ESD (and EMI) protect long slow lines

I'm designing a measurement and control board to interface with an old (70s) PLC. The board consists mainly of I/O ports, both analog and digital in- and outputs. To have my boards not fried by the ...
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0answers
992 views

LC circuit VS CL circuit low pass filter

Are these two topologies for LC low pass filter equivalent? simulate this circuit – Schematic created using CircuitLab simulate this circuit I mean, if I got a switching source, is it the ...
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414 views

Transfer function of EMI filter

In order to define the transfer function of an EMI filter, I want to know if I need to define the equivalent circuit in CM and in DM to calculate the total transfer function of the filter below:
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65 views

Wiring Organ; Electrical Interference?

General Description (A rough block diagram is linked below.) I rewired my organ with digital electronics. I have a microcontroller (Teensy LC) that is used to scan the keys (pressed or not). It ...
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1answer
80 views

Intentional RF emitter failing unintentional emission test?

Suppose a commercial product uses a FCC pre-certified WiFi module. If the quality is not consistent throughout the batch, I'd guess some pre-certified modules may produce unacceptable emissions. In ...
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188 views

Do I need anything between a microcontroller and a basic FM transmitter to cut out EMI?

Below is my circuit of a basic FM transmitter attached to an output pin of the AT89C2051 micro controller. I haven't tested it and I might decide to connect R1 to the NPN collector instead of to VCC. ...
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73 views

EMI Noises - when controller is powered up

I have one sensor which I need to interface with my controller using SPI communication. The manufacturer of the sensor tells that both controller and sensor should be on same PCB. When we asked ...
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0answers
282 views

Basic surge and overvoltage protection

My requirements are: protect the device from surges according to IEC 61000-4-5 Class 2 protect from 400VAC long term overvoltage (working voltage is 220VAC-15%...230VAC+10%) IEC 61000-4-5 Class 2: (...
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104 views

Image current and return current

I find I'm a little confused about "image current" and "return current" in PCB/EMI/EMC design. Are they equivalent? Many docs use this model when talking return current Exactly, I will treat the ...
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0answers
79 views

Is 'RFI' a term in active usage, or is it all 'EMI' now?

I'm studying capacitors in some detail just now, and one of their typical uses, of course, is to bypass high frequency interference at sensitive circuit inputs. I want to get my terms straight, and ...
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73 views

EMC shielded box with transparent window?

Is there such a thing? I would like to put my board in a box to isolate it from radiated emissions externally and also limit emissions from the board to the outside. I would also like a transparent ...
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0answers
152 views

Latch-up and ESD protection for power supply and RS-422

I am designing a power supply board that has a switching regulator and four LDOs. Now, I understand that layout details or practices will help reduce switching noise from corrupting the ground and so ...
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0answers
1k views

Switching power supply layout review

In a previous question where a SMPS based on an LM5118 was presented, some aspects of the layout were pointed out as being problematic. I've taken another look at the layout of that section of the ...
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149 views

Will the following circuit cause EMI-problems?

I'm trying to get a feel for which circuits will have EMI-problems and which won't. To make things a bit more concrete, I've designed a super-simple LED-blinking circuit using the PIC16F1788 micro-...
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111 views

How can I improve conducted emission caused by a bad primary electrolytic capacitor?

I recently got the job to find out how to pass conducted EMI tests with a bad electrolytic capacitor after the rectifier in a power supply. The background is of course, that the new type is cheaper ...