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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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1answer
73 views

EMC conducted emissions go up if input cable is close to inductor

I am measuring conducted emission at the input of a SEPIC converter. At first, the emissions are only about 45 dBµV at switching frequency. But when I put my finger on the SEPIC (coupled) inductor,...
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141 views

ACM2012-900-2P filter can be used on USB 3.0 lines of a Type-C connector?

I have doubts that this CMF is recommended for USB3.0 due to his bandwidth. I am afraid it will filter the USB signal. Can someone explain better the SCCC21 and SDS21 characteristics from here? https:/...
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47 views

Would any voltage be induced in this scario due magnetic coupling?

Imagine a source with a 100 Ohm source impedance is coupled to an amplifier/receiver which has 1Meg input impedance and the transmission is done by using two parallel wires signal and return |XA| and |...
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194 views

High current ferrite beads

I've found ferrite beads work great for eliminating high frequency noise on the input and output of DC-DC converters, but now I have a DC-DC converter that is outputting 20A and ferrite beads work at ...
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2answers
231 views

EMC CISPR 14 conducted emissions terminals

I'm trying to improve my understanding of the CISPR 14.1 EMC test procedures and requirements, with a view to performing precompliance testing. In particular, I'm looking at conducted emissions ...
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386 views

SCR switching conducted emissions

I have a circuit that drives a 240Vac line to line power to a resistive load. I am testing for radiated and conducted emissions. Radiated emissions went fine but conducted emissions failed with "broad ...
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132 views

RF Interference and Metal Enclosure

We have a product (optical detector), one client had an issue with false alarms due to their radios they use on site. Did some modifications, added a ferrite bead to the cable and put a driven guard ...
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1answer
78 views

EMC testing of polarity detecting circuit

I am in the process of building a prototype and need advice on best way to ensure passing EMC testing the first time. I am what most would consider a hobbyist and I am doing this project on a ...
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439 views

What causes 1000Hz (and multiples) electromagnetic interference?

When recording old analog synthesizers (different brands and models) I'm getting interference in the audio. This started suddenly about two years ago (I thought the synth I was using was ...
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1answer
87 views

24VAC vs 220VAC inductive voltage transient

I'm designing a PCB with a PIC micro-controller that has to switch some contactors. This PIC drives some NPN BJT transistors and these transistors drive some Relays that switch the contactors. I'm ...
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104 views

Avoiding EMI with crammed radio PCB design

This is the PCB I'm almost ready to put into production. In the picture, the parts are laid on a 1.27mm grid. Every component and track has at least 10mil clearance. The smallest track size is 10mil. ...
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259 views

Noise Reduction in Transformer Circuit

I am using below scheme for generating different voltages using transformer. T1 transformer generates 15V and 48V ac and then rectified by AC-DC converter to generate different DC voltages (12V_Op ...
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1answer
94 views

Why isn't solid permalloy used for common mode chokes?

When reverse engineering a common mode choke from a line filter I found a wrap of very thin metallic foil inside the plastic housing of the toroid core. A little research on magnetic materials ...
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3answers
59 views

Is better to have holes on different sides of the shield instead of the same side?

I suppose the best is to have no hole on the shield, but that is practially impossible if you have to let cables come out of it. So I read somewhere that having the holes on different sides of the ...
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299 views

Power supply for Precision Current Source for Medical Instrument

I am trying to implement power supply for constant current source(LM334) for medical application. I have 24V,3A SMPS to generate required output (38V) to operate LM334 Constant current source of 10mA. ...
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2answers
684 views

Chassis grounding for multiple daisy-chained units

I'm designing a system that provides power/ethernet/serial for up to 5 daisychained units. All of the boxes will be metal and my initial plan is to run power and signal ground through the 14 pin ...
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172 views

ferrite core replacements with passives

I am using a ferrite core to remove video noise in an NTSC video system. I am using the ferrite core on the video and video GND lines. I am merely winding the video and video GND lines on the ferrite ...
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1answer
1k views

Direction of E1 and E2 in phasor diagram of transformer

The phasor diagram of transformer is a bit confusing. Is E1 and E2 have same direction? Different books mention it differently. Please clarify!!
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2answers
996 views

Suppressing interference in a pressure sensor circuit

I just looked over a circuit designed by my predecessor, which is used to interface with a pressure sensor. It works, but I have some doubts about the way the input filtering is done. The simplified ...
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1answer
70 views

Understanding the mathematics in the following article about EMC

I am currently studying the following reference about EMC, and try to understand the mathematics done in chapter 2 "What do we mean by high speed". The link to the reference is given below: ...
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1answer
65 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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1answer
39 views

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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1answer
538 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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2answers
960 views

How to convert 12v dc to smooth, as if coming from a battery, 6v dc (EMI – RFI free)

I’m an electronics newbie. I did a very simple project. In order to convert 12v dc to 6v dc I used one of those step down converters. Unfortunately what I’m trying to power is an AM radio. It power on ...
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4answers
100 views

EMI Input filter in SMPS

While reading some application notes and standards about EMI Input filters, and from the fact that: Engineers are responsible for ensuring that a circuit can operate properly in the presence of ...
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2answers
2k views

how to deal with the EMI issues in the 16X2 LCD display?

I'm designing a product with 16X2 LCD display and it shows the junk characters when i switch the 3-phase contactor ON/OFF through the relay.How to solve this issue through software or hardware ...
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2answers
2k views

unbalanced audio - shielding and ground loop for 2 ch

I have a 3 conductor wire that are all wrapped in a foil shield with wire conductor, for a total of 4 wires. I am connecting the 3 inside wires to audio left, right, and ground. This is an unbalanced ...
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3answers
61 views

Transistor with PWM vs LED driver for LCD backlight

I'd like to design a circuit that utilizes a small 1.3" LCD display with maximum LED backlight forward current of 40 mA. Since I'd like to use brightness control, I am hesitating between using a ...
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2answers
55 views

EMC/EMI tests should be applied to power transformers or not?

I'm currently working in a naval industry. I see that EMC/EMI tests aren't applied to many of the transformers in combat ships. I wonder, is there any logical reason or explanation for this? I also ...
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1answer
76 views

Difference in signal speed for a high speed signal when it is driven as single ended and differential?

This is a thought experiment. I would like know and what will be the bit-rate in differential channel when signal is driven differentially and in single ended mode? Lets there is differential trace ...
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0answers
26 views

UPS and server at different Aperages [migrated]

I have bought a DELL EMC PowerEdge R740 server which hosts: 2x Intel Xeon SKL-EP Gold 6130, 1x NVIDIA Tesla V100 32GB, 12x 8GB DDR4-2666MHz ECC RAM It has one main and one backup power supply each @ ...
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1answer
66 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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4answers
1k views

Wrapping data cable around ferrite rod

I am trying to do some high quality audio recording using a fire wire interface. Currently I have a naked firewire cable. I was looking on eBay for some ferrite cores and that got me thinking about ...
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2answers
72 views

Bluetooth bothered from the next house ... plausible? Solutions? [closed]

I have two computer sitting in a room at one end of my house. I typically connect a bluetooth trackpad to each, and a bluetooth audio box to one. Every so often, bluetooth communications are ...
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1answer
96 views

how can i attenuate mobile signal completely(maybe 90%) and please suggest me the wall thickness ,as i want to use copper or aluminium [closed]

please help me as i want to make a den for my dog that completely attenuates em waves of phone
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1answer
238 views

Need help to newbie to understand MIL-STD-461 [closed]

why only 10khz-10Mhz is used for CE102 test ? why not other frequency range is used for CE102 test ?
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2answers
167 views

Avoid EMI in power circuit controled by MCUs

This is a toy project just for fun. As anybody knows, if I want to control a lamp by a simple switch, the circuit is as follows: However, I want to change the circuit so I can control a lamp with a ...

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