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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11
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1answer
1k views

Weak internal pullups on microcontrollers and EMI susceptibility

What disadvantages can I run into when using weak internal pullups (100k) on microcontrollers? I'm wondering how susceptible lines (with only parasitic trace/component capacitance) become to EMI ...
15
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1answer
15k views

PCB Ground and Power Planes

I am desigining a 4-layer PCB with the following stack-up: Signal Top, Ground Plane, Power Plane, Signal Bottom. This is the first PCB I make like this, which includes a noisy SMPS with a switching ...
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2answers
488 views

EMC Design Precaution

I'm designing a simple circuit which will charge a big capacitor for 3 seconds, then pass a 5A current for few microseconds, then charge again the big capacitor for 3 seconds, then pump again 5A for a ...
13
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2answers
1k views

Best way to group power pins on a connector?

I am designing a little mezzanine PCB that uses Hirose DF12 connectors to connect to the motherboard. Four different voltages are delivered to this PCB: ±10v, 3.3v, 48v (and ground). They go through ...
1
vote
1answer
388 views

Running Microwave Oven interupts Wifi connection. Should I worry about it? [closed]

Every time I turn on microwave oven, Wifi connection to my computer is disconnected. When the oven's done, Wifi recovers. This means the microwave somehow floats in my home when it's running. Should I ...
3
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1answer
432 views

What EMC considerations need to be made with RF bias-t with 3-4A of current consumption?

After getting a great answer on how to couple a signal on to a DC line, I wonder what EMC considerations that has to be done with using a bias-T circuit used for communications with a ~130kHz QPSK ...
-2
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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 ...
3
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2answers
771 views

Different ringing patterns on flyback output

A modified version of the PCB that I discussed on this post was implemented. It is still 2-layer with all components on top and the ground on the bottom layer. The transformer windings were directly ...
15
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1answer
7k views

To “ground fill”or not to “ground fill”?

I have been reading up on the EMI issues in Electromagnetic Compatibility Engineering by Henry Ott. (wonderful book btw). One of the topics "PCB Layout and Stackup" (aka Ch 16) there is section about ...
8
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1answer
1k views

Is my design good enough in terms of noise and EMI as its 80MHz MCU board [closed]

Recently I'm trying to design a PCB board for an MCU. The problem is I haven't considered any noise aspects before. As I'm in a contest for new electronics product run by our university I have to ...
2
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1answer
190 views

Can a transformer be placed next to RF module?

I'm planning a PIC-based power measuring circuit that will transmit measured data through an RF module to an other PIC. I'd like the circuit to be placed inside one of those casings in which you can ...
1
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1answer
2k views

emi standards/best practices for PC cases

According to an EE friend, the FCC specifies EMI tolerances (max outputs) for PC components, including cases. However, here it says that there are standards for a number of components but not cases. ...
21
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2answers
9k views

Via fences for noise reduction of a chip antenna?

I'm working on a 4-layer PCB that has a wifi module and a chip antenna, the antenna is placed at the corner of the PCB and the copper beneath it is removed, I see that via fences are used on the ...
18
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3answers
7k views

What problems could occur when chaining 40 shift registers?

I'm planning on chaining together 40 x 74HC595 shift registers. The whole chain of 74HC595s will be controlled by a 5 V microcontroller, which will generate the SDI,...
8
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2answers
30k views

EMI Filter calculation in a SMPS

I am building a SMPS using the fairchild Semi FSGM300N Power switch. FSGM300N Datasheet If that datasheet link is walking wounded try FSGM 300N datasheet I used the design tools provided by fairchild ...
31
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2answers
3k views

Ground ring — good or bad?

Here are two routings: Which is better? On one hand, the first is bad because ground ring is one-turn coil, hence induction current will be appear. On other hand, the second is bad because potential ...
6
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1answer
2k views

EMI filter for 1-wire

I have made thermometer with 1-wire sensor (DS18B20). The sensor connected to microcontroller via long (approx. 4m) three wires (GND, VDD, DQ). The wires has no shield. It works, but I worry about ...
7
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1answer
2k views

What inductor to use?

I'm working on a device utilizing Atmel's AT32UC3C microcontroller. The datasheet and design checklist documents provided by example schematics utilizing some type of RF/EMI inductor to isolate the ...
1
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1answer
687 views

RF Module and EMI

I am using a RF module in a design with several switching regulators. My implementation is as follows: When the switching regulators are on (and heavily loaded at approximately 500-700 mA) the RF ...
3
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1answer
221 views

Surface mount bead core

I am experimenting with surface mount components for a project. All the other components seem to be OK and I have deduced that it is the surface mount bead core that is the problem. When I remove ...
5
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5answers
2k views

Calculating resistance in decibel

In EMC there is an equation for charactristic impedance (If I am not wrong) that is defined as: $$Z_w = \frac{E}{H}$$ As you know \$E\$ is expressed in Volts and \$H\$ as Ampers. I had the exam ...
9
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2answers
2k views

How to check whether a component can work in strong magnetic fields?

I want to design my PCB to operate nicely even when we place it next to a neodymium magnet. How to check whether my component can work in such condition without shielding? Edit: I haven't face any ...
24
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2answers
3k views

Alternatives to SPI because of EMI

I currently make a system consisting of a plastic enclosure which contains an MCU talking to 7 ADCs using 2MHz SPI over wires about 5cm long. The problem is that I'm concerned about EMI. Everything ...
6
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1answer
906 views

Very small scale electronic goods manufacturing regulations

I would like to make a 12v rechargeable battery operated robotic toy, for sale as a kit. This would be more of a hobby for me, selling say 5 units a month with a very small turnover. It would just ...
4
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1answer
5k views

How can a shield winding in the transformer be helpful without fully covering the core?

This article describes the Apple iPhone charger circuitry in great details. It mentions the shield winding in the flyback transformer. The shield winding is simply an extra most outer winding and the ...
8
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1answer
4k views

Capacitor and ferrite beads when to use which?

In this question Ferrite beads used to filter high frequency noise. Capacitor also can be used to reduced noise and filter out high frequency noise. Are they have the same effect on filtering high ...
8
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4answers
1k views

Can I create a backside “copper polygon” of the switch node in an SMPS?

I have an SMPS design that has the following properties: 9-15V input voltage 5V, 3A output Switching frequency is 350kHz. Switching controller is a LM25085. The diode used is a DSSK48-003BS. The ...
0
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2answers
691 views

STM32: Running many peripherals at the same time

I need to do EMC testing for a board controlled by an STM32F2. Ideally, I want to activate, full-speed, every peripheral on the board. That is, I want to be reading/writing as fast as possible to the ...
7
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5answers
13k views

How can I improve USB EMI insensitivity?

I have several devices and some long cables on my PC's USB buses and every now and then I get a message like ...
3
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2answers
386 views

Performance Analysis of PLC Modem

I'm an electronics and communications engineering student undertaking a project regarding the occurrence of Electromagnetic Interference (EMI) in power line communications (PLC). I would like to ...
3
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2answers
15k views

How is quasi peak calculated

As said in the headline, how is quasi-peak calculated? I was not lucky on google this time, so I will ask here. I'm just looking for the formulas behind the calculation, since I want to make some ...
0
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1answer
171 views

Are LCD/Plasma/Smartphone monitors susceptible to EMR eavesdropping?

Having just read about EMRTempest eavesdropping; I find myself wondering whether EMR eavesdropping is defeated by FCC regulations on interference With the advance of technology from CRT to the newer ...
2
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1answer
350 views

Current rise time. How fast is too fast?

I'm trying to create a suitable response to Pumping a few Amps for a 100usec. The OP wants to create a 5A current pulse for 100us. They want to have a current rise time of 1us at the start of the ...
9
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3answers
24k views

How important is the shield on an RJ45 connector?

If I am going to use a PCB mount RJ45 connector for 100mbps Ethernet, does it need to be a shielded connector, or can I get away with using an unshielded one? Is there some standard which deals with ...
10
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1answer
1k views

How close do I really have to place a 25MHz crystal?

I'm laying out a very space constrained PCB. Normally I would place a 25MHz crystal absolutely as close as possible to the chip using it. However, on this PCB, something else really needs the space ...
1
vote
1answer
653 views

Isolating BNC connector from test shield

For my project, I need to have BNC connectors on the test metal shield. So what I did so far is drilling holes, and mounting BNC connectors on it: I used some hot shring on the part which passes ...
13
votes
1answer
7k views

How to shield microcontroller from electromagnetic interference

I'm working with high voltage circuit (2.1 kV for defibrillator capacitor testing) and I'm controlling power supply with arduino, reading required information from laptop using serial interface. Most ...
8
votes
3answers
654 views

Is it safe to run long I/O wires to a microcontroller?

I'm contemplating using an MCU sitting in my garage to read data from a couple of sensors, one of which may be as much as 10m distant. I'm not using analog sensors, as this question asks, instead, I'...
4
votes
3answers
918 views

At what point does the responsibility of the manufacturer end with regards to FCC/CE testing?

I'm curious as to when the responsibility of a manufacturer ends when dealing with emissions and RF testing, part of FCC and CE tests. I repair TVs as a hobby and as business. I got a TV in from ...
3
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3answers
1k views

safe to use an unshielded jack for 10Mbps Ethernet?

I have a hardware device which includes Ethernet connectivity. I have a surface-mount Ethernet jack, with top entry (as opposed to right-angle). Part number is RIA Connect AJS03B8813, if that helps. ...
4
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3answers
3k views

How can I design a robust and professional power supply circuit?

I'm planning on doing a large project that would include an ARM microcontroller @ 50 MHz interfacing with a graphic LCD, user buttons, some sensors and some actuators (DC motors, valves) controlled ...
12
votes
1answer
4k views

PCB 'Emi proof' design

Currently I'm designing a GPS basestation which will have a radiomodem (broadcasting at 407-480MHz), a ARM7 microcontroller running at 60MHz and a FTDI USB chip. The FTDI USB chip even runs at 480MHz ...
4
votes
1answer
333 views

Looking for good articles about reducing crosstalk and other noise in PCB design

I am designing a rather large PCB with straight parallel traces 20cm long carrying CMOS logic at around 100kHz. On top of that I have 8 MOSFETs supplying 5A switching on/off at around 400Hz which a ...
18
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2answers
4k views

PCB routing: EMI and signal integrity, return current questions

If there's any EMI/SI lesson I've taken in, it's to minimize return loops as much as possible. You can work lots of EMI/SI guidelines from that one simple statement. However, not having or ever even ...
9
votes
7answers
1k views

If mobile phones have to go through such extensive FCC/CE/EMI testing, why do they interfere with my radio?

It seems that to sell a GSM mobile phone, companies like Apple, Motorola, Sony Ericsson and many others invest a considerable amount of money in EMI testing them. Yet they still interfere with my ...
5
votes
4answers
3k views

Is there a way to protect RS-232 Transceiver IC from static death

My company sells devices many devices that use RS-232 line transceivers like the MAX232 chip. In many cases our users run their RS-232 cables in the range of 30 to 50 feet to connect our device to ...
2
votes
2answers
529 views

Why would a power supply mess with my scope?

I recently bought a 0-35V 0-3A (105W) CC/CV linear power supply, made by Takasago in Japan, second hand. It's a nice unit, and inside of it is a massive power transformer along with three pass ...
2
votes
1answer
236 views

Detecting surrounding electronics or electrical devices

I'm working on a project which requires using EM antennas or sensors array to identify and locate surrounding electrical devices such as cellphone, laptop, ipod, remote... I'm not a EMF guy. I don't ...
4
votes
2answers
502 views

What's the cheapest way to do basic EMI testing?

I need to test that my project will not interfere with radios in the 27 - 72 MHz band. I can't afford a spectrum analyser. Nor can I afford to buy all tx/rx pairs in between 27 and 72 MHz (27, 35, 47,...
2
votes
1answer
1k views

LC Filter for Phase Control

Can you point me to a good online resource to learn how to understand and design LC filters? The goal is digital forward phase control to dim a light bulb. I've read that the EMI produced by the ...

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