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 ...

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Resistance and Inductance of a ceiling fan motor needed to spec snubber

I'm looking to specify (well, suggest) a RC snubber network for someone over on diy.se who is having EMI problems with his ceiling fan knocking out his TV briefly on turn-off: ...
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32 views

EMI/ESD protection for USB interface?

I'm a student making a simple Arduino-compatible board similar to the Pro Micro and am going to put a USB connector on the board. The schematic in the above link doesn't show any kind of EMI/ESD ...
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1answer
74 views

Reducing EMI Radiated & Conducted

I have a switching regulator that operates at switching frequency of 260Khz that steps down a 28vdc to 3.3Vdc. The switching regulator output will supply current as high as 1 amp for the initial 5 ...
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62 views

Can a toroidal transformer be wired as a common mode choke?

I am looking to build an ac power line conditioner. It was suggested that I use a transformer with dual 6.3v secondaries wired in a common mode choke configuration. This is done by using the in-phase ...
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55 views

How to shield a USB device from high EMI

What is the best way to keep a USB device from disconnecting when exposed to a high EMI environment, such as when connected to a high voltage power supply under test? For example, in debugging a ...
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185 views

Electrical noise on guitar pickups from computer. Due to radio interference, or inductive coupling?

When I point my guitar pickups towards my desktop computer from several feet (2 1/2 - 3) away, I can hear a lot of buzzing/clicking, depending on what the computer is doing (idling vs, say, playing ...
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51 views

SMPS transformer orientation with respect to PCB: what's best for EMC?

I have the option of either using a vertical or horizontal bobbin for a flyback SMPS transformer, and I can't conclusively decide which would be best for minimal radiated interference to be picked up ...
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347 views

How to fix EMC problems for existing designs?

I'm going to be looking at a few products that have failed EMC radiated emissions testing and will need to apply fixes in order to make them pass (unfortunately, in these cases, two of the designs ...
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52 views

EMC, resistors and trimpots

I trying to get EMC certification and stumbled upon problem. In the above circuit, they will apply ESD to the exposed part of the trim pot, and it permanently changes the value of the trim pot and ...
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59 views

interference proof voltage regulated current source

I want to dim some LEDs, using the PWM output from a microcontroller. There are some more LEDs than in the schematic, already wired, so that they need nearly 12 V to give maximum light at about 50 mA. ...
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44 views

Making conducted EMI measurements in the presence of building-wide ground-fault protection for personnel?

As is documented here among other places, the Line Impedance Stabilization Networks used to make measurements of conducted EMI as per CISPR 22, FCC Part 15, and suchnot contain large line-to-ground ...
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72 views

Effect Of Electronic Devices In Close Proximity

From reading other posts, it seems like electromagnetic induction is the greatest threat to electronic devices these days with either traditional HDDs or newer SSDs. Since current in a wire creates ...
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31 views

EMI/EMC filters for different frequency sub-circuits

I am designing a PWM based solenoid controller. The PWM controller works at 23kHz with an average circuit consumption of 23-45mA. The PWM controller is powered by a non-isolated SMPS with 12V output ...
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31 views

Cable screen terminations for enclosure containing SMPS and instrumentation signal conditioners

I'm looking for some help with some screening and cable termination decisions I need to make. I'd be grateful for any advice, and I'll do my best to explain myself clearly. I am building a control ...
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76 views

Earth alternative

I'm designing an industrial machine which is AC motor derived. There are sensitive analog sensors (e.g. Load cell) in the system and in the user's site, Unfortunately earth connection is not ...
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74 views

How to calculate EMI filter (ferrite bead) specs for digital signal?

I have a small project of mine that deals with plain old VGA output (d-sub). In my project I'm using a CM2009 IC between actual VGA controller and VGA output connector. It's mentioned in the datasheet ...
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41 views

EMI & ESD protection for 3.3V signal

I am looking into options to protect the outgoing signals against ESD events and EMI issues. The device will be battery powered but GPS and radio modem are likely to be operated close-by. Frequent ...
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1answer
38 views

What's the correlation between spectral graphs produced using near field probes and ones produced using an antenna?

I've been looking at getting some equipment for EMC-precompliance on a budget (about £5k). I understand that I can get a spectrum analyser with some EMI options and some near-field probes (about £2k) ...
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706 views

What is the purpose of holes on edge of the PCB?

Here is a photo of one of Texas Instrument's RF EVMs. Please pay attention to edge of the PCB that has multiple tiny holes. I marked 3 of them with a red circle on the photo. What is the ...
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27 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
45 views

Magnetic flux outside a solenoid perpendicular to the direction of axis of solenoid

I know that using straight forward Biot-Svart law it is possible to calculate field inside a solenoid or at a point on an axis away from the circular coil. Now is it possible to calculate the Flux ...
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79 views

Why the \$F_{knee} = 0.5 / T_{r}\$?

In "High-speed Digital Design - A handbook of black magic" p. 2, The knee frequency for any digital signal is related to the rise (and fall) time of its digital edges, but not to its clock rate: ...
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71 views

Thickness of low frequency Mu shield calculation

I am dealing with a low frequency varying magnetic field, say 10 - 100Hz with a magnitude of 0.8T. It seems shielding at this frequency gets tricky. Even though Mu is capable of doing it, there should ...
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71 views

Switching power supply using faraday cage and EMI protection?

Several switching power supplies in the market use this kind of cages to protect the circuit, however, i have this question, A) Is this used as a faraday cage due to the high frequency used by it? ...
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84 views

How to maintain EMI shielding whilst penetrating the shield with cables?

I'm trying to shield an ip camera from EMI generated image noise for low light photography. It's enclosed within a metal box that is then grounded. The subject is also inside the box. The camera ...
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106 views

How do I protect digital design from EMI?

I have built a system that controls a 3 phase induction motor. Unfortunately I don't have schematics, but the system is simple: A 24V DC contactor switches AC to the motor. 24V is fed by a separate ...
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46 views

How much electromagnetic interference/pollution is produced by home power-line network adapters?

How much electromagnetic interference/pollution is produced by home power-line network adapters? How do they compare for example to WiFi routers? They operate on high frequencies to achieve high ...
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51 views

Current-Mode Logic Explanation

I was reading about the HDMI standard and therefore the CML logic, and some alegations are not clear for me about the advantages of the CML. One of its advantages is the low output voltage swing, so ...
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1answer
66 views

LT1084 as Current control Regulator

I am using LT1084 as a current control Regulator. Circuit shown below Since the transistor Q2 is controlled by a PWM pulse so output voltage of LT1084 is varying as shown below Since it is used as ...
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87 views

EMI due diligence

I had an idea to use the World Semi WS 2801IC used for addressable led strips with a power mosfet driver so that each address can be tied to a high current (~1-1.5A) load. The chip indicates the PWM ...
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1answer
195 views

How is EMI avoided inside of an IC?

I was re-watching this video about how CPUs are made and at the time of the video the link points to, I thought "Isn't there some EMI problems with all those transistor signals flying all over the ...
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1answer
58 views

Why a ground loop a problem, not a ground plane(patch attena)?

The question is as the title says: I see various material saying using a solid ground plane. Why would not that be a problem, since a solid ground plane could be a patch antenna?
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171 views

loop area and EMI

I always hear something like "reduce the loop area" when reading materials on EMI reduction. Why we need to minimize the loop area? I have two guesses: Smaller loop area will influence less signal ...
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2answers
145 views

EMI in charge pump switching regulator

I want to use a charge pump to convert 5V to regulated 3.3V output. The charge pump I want to use has the switching frequency of 1200 kHz max. Do I need to be concerned about this switching frequency ...
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1answer
122 views

EMI suppression low frequency

I'm dealing with a PWM generator which drives a load at 12V with pretty high currents (5-10A) The PWM frequency is in the band of 100-200 Hz. Which is the best choice and right configuration of ...
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1answer
64 views

Terminating SDRAM on opposite side of board

I have a 4-layer board with the micro and sdram on opposite sides, the ram signals are short, but I still want to terminate them (I can test the board later and determine if I really need ...
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234 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 ...
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1answer
82 views

Connection between metal enclosure and 0V in industrial system?

I have been testing an industrial system. I have developed a test device to properly test this industrial system. I am currently finalizing the test device and have put it in an enclosure to EMC proof ...
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1answer
91 views

EMC Design of Aluminium Enclosures

When designing Aluminium enclosures (rack mounted units), I've previously used an Iridite NCP finish to ensure electrical conductivity between panels (i.e. no oxide). Does anyone have any papers or ...
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1answer
72 views

Should the ground plane of a noisy mezzanine card be connected to the ground plane of the main card by metal mounting hardware?

I have a mezzanine card, 60 by 40 mm, mounted near one end of a main PCB, about 160 by 40 mm. This card is a known source of EMI problems and, in fact, has a metal shield over it. But, I suspect ...
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2answers
282 views

Can smd ferrite beads be avoided [closed]

I am redesigning an input interface circuit for digital input. Its a basic signal conditioning circuit for reverse polarity protection, EMI ESD protection, and filtering voltage surges. For EMI EMC, ...
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2answers
220 views

3.3V UART over 20cm ribbon cable inside an enclosure - EMC considerations

I am currently designing a device which internally consists of two circuit boards inside a fairly large, grounded metal enclosure. I'm designing one of the boards myself, the other is a bought part ...
2
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1answer
221 views

Long wire PWMed LED lights

so I plan to build a house (at some point in future) and I'd like to implement some sort of home automation. Now one of the things I'd like to have is PWMed lighting. Most of the lights would be 12V ...
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1answer
243 views

PCB layout for 8-16MHz crystal very near WiFi module AND small DC motor

I'm designing an "Internet of Things" appliance where space and layout are constrained by mechanical and cost requirements. The main processor is a PIC18 and its crystal (probably 8MHz, maybe 16) is ...
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2answers
121 views

Optimal PWM Frequency for EMI & EMC

I am planning to design a 65W power supply which will use a PWM frequency of around 100kHz. I am specifically concerned about conducted EMI (not as much about radiated for now). I am currently ...
6
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1answer
235 views

Tying ground planes together with a non-zero Resistor

I was reviewing the schematic of a motor driver board and noticed that the digital and analog grounds are tied together with a 3.9 ohm 1/4 watt resistor. I am still trying to find the gerber files to ...
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2answers
169 views

EMC testing of unenclosed PCB assembly

What is the most common practice in performing EMC tests for PCB assemblies that will be sold without a housing? In my case it is an FPGA development board. Is it possible to design excessive ...
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1answer
356 views

eeprom data corruption during power failure

I recently found a problem with eeprom of a PIC16F877A which is used to control the speed of a dc motor. The drive is supposed to work on the last set speed even if the power fails. But the problem is ...
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45 views

How to shield from electro surgical generator in close proximity?

Looking for help EMI hardening a SERDES interface in close proximity to electro surgical instruments. I believe there may be tips or reference designs from existing pacemaker applications that may ...
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54 views

LED selection for EMI/EMC considerations

For my system, I need to select panel-mount LED indicators which needs to withstand through EMI/EMC tests. Can I use normal panel mount LEDs coming in aluminium threaded sockets for my application? Is ...