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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1answer
36 views
common mode choke inductance question
In a common mode choke, my understanding is that common mode currents will produce fluxes that add together, which increases the effective inductance between them and so attenuating these currents.
...
4
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0answers
108 views
Placement/routing of decoupling cap straddling oscillator guard ring on dsPIC
Changes in my design are forcing me to replace my 44-pin dsPIC33FFJ16MC304 with a 64-pin (same package size, finer pin pitch) dsPIC33FJ64MC506. In the datasheets for both chips, Microchip recommends a ...
5
votes
3answers
147 views
Is it better to have a poor top layer copper pour or no copper at all?
For a few small 2 layers boards I'm doing, I'm using the top layer for parts and signals and a ground pour on the bottom layer with no or very short traces, based on comments and answers to my ...
0
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2answers
98 views
Effect of radiation detectors on electronic components
After the Fukushima nuclear disaster that took place in Japan in 2011, any imports from there are checked for nuclear radiations using radiation detectors.
I recently ordered components from Digikey ...
2
votes
0answers
38 views
Digital RGB interface EMI filtering
Consider the following system:
where:
The motherboard contains a LCD controller (SSD1963 from Solomon Systech) and other components (application processor, solenoid drivers, power supplies, etc.)
...
2
votes
3answers
105 views
TFT LCD pixel clock filtering
I would like to know how to filter the pixel clock in order to reduce emitted radiations.
Block diagram
The LCD controller is part of a motherboard. A board, connected at the other side of the FFC ...
11
votes
5answers
421 views
Why does a simple conductor start to emit EM waves when carrying a signal?
I understand that on circuit board traces with a clock, if the higher harmonics have sufficient power, it results in electromagnetic waves being emitted from the traces which creates EMI. What I don't ...
1
vote
0answers
38 views
Parallel, low noise motor driver design with L293D [duplicate]
I'm designing a very basic motor driver circuit for 12V DC brushed motors to be connected with my microcontroller. The motor needs to be driven in forward and reverse
My objective is to do that with ...
0
votes
2answers
83 views
PWM controller to meet EMI/EMC regulations
I'm designing an application in which the current running into a load is controlled by PWM.
A microcontroller generates a PWM cycle at 20kHz and this signal is used to control a MOSFET which is ...
3
votes
2answers
111 views
Return current in 8 Layer stackup
I have to design a multilayer Board (8 Layer). This is a part of 4 PCBs in a product with plastic enclosure. The high speed signal on PCB are Ethernet, USB2, LAN and UMTS integrated modem. Product ...
8
votes
1answer
175 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 ...
5
votes
1answer
431 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 ...
1
vote
1answer
111 views
EMC Design Precaution
I'm designing a simple circuit which will pass a 5A current for few Microseconds.Then after this it will charge again the Big capacitor and for 3S interval it will pump again a 5A and goes on.
And ...
10
votes
2answers
222 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 ...
1
vote
1answer
173 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
votes
1answer
89 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 ...
-1
votes
3answers
140 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 ...
1
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0answers
97 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 ...
8
votes
1answer
364 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 ...
6
votes
1answer
342 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
votes
1answer
110 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
vote
1answer
140 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.
...
8
votes
2answers
472 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 ...
9
votes
3answers
504 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 ...
4
votes
2answers
2k 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 ...
20
votes
2answers
483 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 ...
3
votes
1answer
208 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 ...
5
votes
2answers
214 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
vote
1answer
142 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
votes
1answer
89 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
votes
5answers
289 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 ...
8
votes
2answers
247 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 ...
16
votes
2answers
486 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. ...
6
votes
1answer
312 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
votes
1answer
426 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 ...
0
votes
0answers
99 views
electromagnetic compatibility and diesel generators [closed]
If one were to deploy one or several diesel generators, what if any EMI can be generated and cause interference in for example HF antennas in close proximity? If there is the possibility of potential ...
6
votes
1answer
501 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 ...
7
votes
4answers
316 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
votes
2answers
260 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 ...
0
votes
2answers
2k 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 ...
2
votes
2answers
187 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
votes
2answers
1k 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
votes
1answer
100 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 ...
1
vote
1answer
140 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 ...
5
votes
3answers
2k 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 ...
10
votes
1answer
331 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
0answers
61 views
External Accessories for VFD
I am trying to decide what external accessories I need for my VFD 7.5 HP for a 1500Watt Vibrator motor. The three options I have come up with are below. I'm using a standard 220VAC line supply from ...
1
vote
0answers
110 views
CFL'S causing pixelation [closed]
I work for a resort with 584 rooms we recently replaced all living room tv's to 42" LG flat screen HDTV's The challenge we are having is freezing picture and pixelation when we plug in a hair dry it ...
1
vote
1answer
155 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 ...
9
votes
1answer
934 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 ...
