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Questions tagged [emi-filtering]

For questions about the filtering of undesirable electromagnetic interference (EMI). Consider using in conjunction with related tags, as applicable (e.g. use with "switch-mode-power-supply" for questions about the filtering of EMI produced by a switch-mode power supply).

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Strange capacitor in Murata BNX filter

I've torn apart an EMI filter from Murata (BNX022-01). Does anyone have any idea what type of capacitor is this? Judging from a datasheet (https://www.murata.com/en-us/api/pdfdownloadapi?cate=&...
dude_ran4er's user avatar
2 votes
2 answers
119 views

Why is it bad to have unconnected metal areas around PCBs/enclosures for EMI?

I've heard that it is generally bad to have unconnected metal around PCBs due to both safety reasons of charge buildup, but also EMI in the sense that these metal pieces can act as antennas and re ...
George kirby's user avatar
2 votes
1 answer
102 views

Telecom Lines Conducted emissions noise travel

I am seeking an explanation of how conducted emissions on telecom lines are measured. The frequencies of interest are at 150kHz to roughly 850kHz. The size of the unit is 30cm by 30cm by 15cm. The ...
DRF's user avatar
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1 vote
2 answers
66 views

LDO vs voltage reference when input signal is noisy

I am designing an active EMI-filter (AEF) with an op amp (LTC6227). The AEF suppresses noise from a DC/DC converter. Ther op amp requires a supply voltage of 9V and a reference voltage of 4.5V at the ...
Schafa's user avatar
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2 votes
0 answers
32 views

Telecom Lines Conducted emissions [closed]

We have rented a Telecom line ISN to conduct some in-house pre-compliance testing. The test setup closely follows the CISPR32 standard. We encountered issues with conducted emissions in the lab, which ...
DRF's user avatar
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0 votes
3 answers
92 views

Why is my encoder showing abnormal spikes on the oscilloscope readings? Any suggestions on what might be causing it?

So to summarize, I have these winch drives that I've put together. One of them went berserk during testing and now I'm diagnosing the problem. I have attached an oscilloscope to where the KEB servo ...
Brandon Ringfield's user avatar
0 votes
2 answers
52 views

3 phase emi filter for analog signal

I'm developing a device that needs to read analog data from a sensor located far away (~ tens of meters). To eliminate conducted noise (150 kHz..80 MHz) I use a ferrite filter on the cable and ground ...
P0nyL0v3r's user avatar
1 vote
0 answers
57 views

Needed Assistance - EMI Issues with 16x2 LCD Display (Model BCB-1602-03C)

Hello stack Exchange Community, I am Yogesh D from Trident Pneumatics Private Limited, R&D Innovation - Electronics. We are currently using a 16x2 LCD display (model BCB-1602-03C) in the ...
Jishnu Prakash Nambiar's user avatar
1 vote
0 answers
64 views

EMI/EMC: Connecting PCB mounting holes to chassis in multi-board system

I am working on a system which has a metal chassis connected to the earth. The system gets power from a dedicated PSU. The power lines of the PSU (VCC_PSU / GND_PSU) are fed into a master PCB and ...
SpongeBob's user avatar
1 vote
1 answer
58 views

Common mode and differential mode filters order

In power supplies input filters the common mode block (typically a common mode choke) is usually placed first, and then the differential mode block follows. The image shows this structure. Is there ...
Isacco's user avatar
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1 answer
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Analysis for the peaks in FFT

Suppose I have 2 cases: 1st MOSFET switches with rise times and fall times of around 10ns (Vds). 2nd MOSFET switches with rise times and fall times of around 50ns (Vds). Both of them have a switching ...
Andr7's user avatar
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1 answer
85 views

Can I use the mains itself as a ground? [closed]

Basically, an ideal EMC/EMI filter looks like the below circuit diagram. Ideal EMI filter circuit: Can I use the mains itself as a ground instead of using a physical ground? My take on EMI filter ...
Mrinmoy Sarkar's user avatar
0 votes
1 answer
117 views

PWM LED Dimming Circuit Design Recommendations and comparison against linear dimming

I want to dim a 5 meters long LED strip reaching all across a room with a PWM signal from an Atmega328p. First the schematic and the specs: Specs: ...
CaveScientist's user avatar
0 votes
1 answer
55 views

Can inrush current of an SMPS damage EMI filters?

I am assembling an electronic product using off-the-shelf components. I want to connect the device directly to the power socket, so I plan on using a switching power supply (this) to get the 12V ...
AjejeBrazorf's user avatar
1 vote
3 answers
113 views

How to filter the ac signal in a dc cooling fan circuit

The cooling fan in a vehicle is powered by a 12V battery. When the fan begins to work, in addition to the dc current, there is ac signals in the circuit, and the frequency of the ac current increases ...
Reboost's user avatar
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1 vote
1 answer
69 views

PI filter for two buck drivers for a low-emi solution

I'd like to save space on a circuit that uses two buck LED drivers. The circuit is designed for a low EMI solution and there are two separate PI filters on each Vin pin (recommanded on the datasheet). ...
msch's user avatar
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2 votes
3 answers
367 views

Current Rating in Common Mode Choke

What is the meaning of this current rating which says "unbalanced" current? I know in common mode chokes the common mode current rating is given. Why here it is written as Iunbal.?
Andr7's user avatar
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2 votes
1 answer
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Ferrite bead on input EMI filter

Here is the schematic of a demoboard : It is a buck converter with an input EMI filter. As you can see it there is an inductor and a lot of capacitors which make an LC filter with a cutting frequency ...
Jess's user avatar
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0 votes
0 answers
36 views

Changing from Through hole to Surface mount component

I have a design that would require a flat backing of our pcb. We are attaching a flex pcb to the back of this board being designed. This caused me to move/change some components from another engineers ...
Wes Ellgass's user avatar
3 votes
2 answers
80 views

Current peak on a low EMI buck LED driver

I'm designing a buck LED driver using the LT8376 and I'm following the typical application for a low EMI solution (page 26). On the output, the schematic proposes a 100 nF capacitor in parallel with ...
msch's user avatar
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1 vote
0 answers
62 views

3m unshielded 3V3 UART

I have a product that probably uses the wrong digital interface, but I'm trying to make it work anyway. Differential signalling, a better cable and other things would be desirable, but that is outside ...
Alexander Ohm's user avatar
2 votes
6 answers
205 views

What is the best 4-layer stack-up for lowest EMI susceptivity?

I plan to design a 4-layer board that will work on an industrial machine. This machine has AC motors driven by commercial AC drives on it. Since the earth ground is very weak at the place, they ...
Semih's user avatar
  • 67
0 votes
0 answers
22 views

Ground in battery powered device interacting with capacitive coupling

If even the ground wire in a battery powered device especially biopotential measuring devices like EMG can attract interference current. Then what is the use of shielded leads that connects to ground ...
Jtl's user avatar
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0 votes
1 answer
72 views

Can 1 inch unshielded wire attract interference current?

In shielded EEG leads, the purpose is to resist capacitive coupling where interference current can couple to the high impedance electrode resulting in significant noise. I read "A typical ...
Jtl's user avatar
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2 votes
2 answers
179 views

My First PCB - EMI Problem on Poorly Earth Grounded Test Place

A PCB design amateur here. Stumbled upon a hard problem right at my first PCB design. I have tried to comply with the layout rules of thumb for SI and EMC, but still encountered with strong EMI ...
Semih's user avatar
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0 votes
0 answers
79 views

ESP32 crashes when starting a 3 phase induction motor through a star delta starter

Circuit Details: An esp32 driving 2 relays(5V SPDT HL JQC-3FC(T73)DC5V) via a darlington array(ULN2803A). The relays are connected to the start, stop buttons on a star-delta motor starter. The motor ...
Saran Rathinavelu's user avatar
2 votes
0 answers
29 views

Why the induced noise is sometimes additive but sometimes works as a constant?

Why sometimes the noise (e.g., induced 50hz hum) is added to a useful signal (thus increasing its 50hz value), but sometimes it works as a noise floor - has a static value and can be overpowered by a ...
Matilda Bentefor's user avatar
1 vote
1 answer
58 views

Y capacitor provisioning when the output is referenced to mains neutral?

I am designing a device that uses a "standard" board-mounted AC/DC switching supply module (on the order of 20-30W), along with a battery backup, to power itself and an attached device, both ...
ThreePhaseEel's user avatar
3 votes
2 answers
238 views

Should the high frequency filter be implemented in the differential signal or is afterward ok?

Should a high frequency filter be implemented on the differential signals input like in the following Olimex EMG/EKG amplifier, or can it be implemented after the Vinput+ and Vinput- have passed ...
Jtl's user avatar
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0 votes
1 answer
91 views

Power over Coax (PoC) filter design calculations

I need to design a PoC filter for one of my project. I am referring this document for the same. Below is the PoC filter given in page in 13. I am using only TI parts. This document is from TI. This ...
Confused's user avatar
  • 2,593
0 votes
1 answer
42 views

Ferrite bead parameters clarifications required

I was going through this document to learn more about ferrite beads. Regarding DC bias in page no 6 you can see the statement given below. "Notice that when 300 mA DC bias is used, the impedance ...
Confused's user avatar
  • 2,593
0 votes
1 answer
57 views

How to mitigate this transient with huge magnitude at turn on interval for a MOSFET tested in double pulse test setup In LTspice?

I am doing a spice simulation to characterize the switching behavior and switching losses for MOSFET I want to use in my three phase inverter application. I am using a 60 V, 3 mΩ Si MOSFET from ONSEMI ...
Alison's user avatar
  • 347
4 votes
2 answers
382 views

Two X capacitors from lines to ground- why? GFCI fault, even after replacement

I'm trying to repair a very old printer (circa 1980). When I plugged it in, the GFCI outlet protection immediately tripped, even with the printer turned off. The hot side of the cord is connected to ...
BZo's user avatar
  • 2,151
0 votes
1 answer
100 views

Is Noise filter needed for CAN passthrough?

The structure is simply diagrammed as follow. My Board provides only routing connecting each connector for other ECUs using CAN channel. My queistion is if i need additional CMCs on the routing. Are ...
min_c's user avatar
  • 1
0 votes
1 answer
134 views

Ethernet PHY design query: Compatibility of DP83848QSQ/NOPB with STM32F407VET6 and pin configuration concerns

I'm relatively new to Ethernet PHY design and currently working on a project where I've chosen the DP83848QSQ/NOPB PHY and plan to connect it to the STM32F407VET6 microcontroller. However, I've ...
user avatar
0 votes
1 answer
207 views

What is the purpose of these diodes in the EMI filter?

What is the purpose of the D1 and D2 diodes in the below EMI filter? I've seen diodes placed there in front of EMI filters so I added the to my circuit, and I want to know the purpose. I have not ...
user353165's user avatar
2 votes
3 answers
201 views

Will a housekeeping flyback require EMI filtering? [closed]

I'm interested in designing a hobby custom power supply in SPICE using a full bridge converter topology. I will have various components which will require biasing, so I was also thinking of using a ...
user353165's user avatar
1 vote
2 answers
89 views

Which material should be chosen for EMI shielding? [closed]

Once while making a machine with a Hall effect sensor, I had chosen a mild steel (MS), powder coated body for the machine. Now I am not blaming the MS body until better scientific proof presents, but ...
Iskander's user avatar
0 votes
1 answer
72 views

EMI suppression from vibration disc motors

In my application I'm using 9V (6xAA batteries) to power three vibration disc motors in series (Solarbotics P/N:VPM2,) some LEDs (not shown) and then to a non-isolated DC-DC buck converter. The buck ...
Leoman12's user avatar
  • 1,158
2 votes
2 answers
186 views

How can a Faraday cage absorb and reflect waves, yet antennas mostly absorb and can be used on signals?

I understand they are very different in structure but comparing a simple monopole to a Faraday cage, they both are constructed from metal. Why is it the sides of the Faraday cage absorb the waves and ...
George kirby's user avatar
1 vote
1 answer
156 views

RF signal on Audio/Music/Guitar equipment

It is looking like the standard RF noise from my (new to me) old apartment wiring through my amp to my speakers. Suspected it could be due to poor guitar shielding/grounding, bad cables etc. Started ...
Daniel's user avatar
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1 vote
0 answers
59 views

Optimization of gate resistance value for gate driver circut of a SiC MOSFET

I am struggling to tune in the RG_on and RG_off values of gate resistors for SiC MOSFET. I have tried a lot to tune in the values but at turn off transition there is persistence high frequency ringing ...
Alison's user avatar
  • 347
3 votes
1 answer
257 views

Shielding bottom of PCB in THT design

I'm designing a PCB where I could use one layer as massive groundplane and shield. Do I have to make some form of shield for THT part pins, or are they small enough to not pickup a lot of ...
Jakub Rogacz's user avatar
1 vote
1 answer
247 views

Do you put a ferrite bead on both the positive voltage and GND trace?

I'm designing some basic DC power filtering for a very simple PCB. Do ferrite beads go on BOTH the positive voltage trace AND the GND trace, or should GND be completely free?
Rydberg's user avatar
  • 251
1 vote
1 answer
143 views

Common mode choke placement for good EMC performance

I am interfacing a deserializer with Quectels smart module. The CSI lines of the deserializer are connected to the CSI lines of smart module. A common mode choke is placed in between them. The ...
Confused's user avatar
  • 2,593
0 votes
0 answers
70 views

Fully isolate digital and analog sections to reduce EMI when driving DC loads with PWM. I2C data corruption

I am working on a mixed-domain portable secret project based on the venerable ATMEGA2560 that will essentially control 3 DC heaters using MOSFETs, communicate with an external controller via UART and ...
Daniel Melendrez's user avatar
0 votes
1 answer
120 views

Do I need to add a filter for an isolated DC-DC converter?

I have purchased three CUI Isolated DC-DC Converters, the models are VHK50W-Q24-S5, VHK150W-Q24-S12 and VFK600-D24-S24. I wonder you could help / guide me to the correct use of them. Questions: I saw ...
j m's user avatar
  • 1
2 votes
3 answers
443 views

How to filter a noisy PWM signal without affecting rise and fall times

I need to read the frequency and duty cycle of a PWM signal that is expected at 88Hz. It is getting a lot of noise (during radiated immunity). Before noise: After noise injected: What filter would ...
wgthompson's user avatar
1 vote
1 answer
215 views

EMI filter attenuation requirement for a buck converter given EMI compliant AC-DC converter

In my application I have an off the shelf 600W 72V AC-DC converter that generates the main DC bus that powers a custom board that houses a 72V input, 9A output buck converter switching at 330kHz. A ...
Dhruv Goel's user avatar
1 vote
2 answers
159 views

Avoid ground loop for multiboard high-current device

Problem overview I am designing a multi-board pulser device for ultrasound, and am encountering a conceptual issue when trying to prevent a ground loop in this device. I added a minimal example to ...
villanif's user avatar

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