Questions tagged [interference]

For questions about electromagnetic interference (EMI); see also the [emc] tag.

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32
votes
2answers
14k views

Does Bluetooth interfere with WiFi?

I've read that WiFi b/g/n is using 2.3995 to 2.4845 GHz. Bluetooth is in between: 2.4000 to 2.4835 GHz. So what will happen when I put a Bluetooth sending device next to a WiFi sending device? Will ...
31
votes
5answers
19k views

How come radio signals don't interfere with each other all the time?

I'm a newbie on wireless technologies and I'm trying to understand how they work. One thing I don't understand is this: How come transmissions from different devices don't interfere with each other ...
30
votes
5answers
24k views

What is causing large oscillations in my DC/DC boost converter? Is this ground bounce or some other effect?

I designed my first PCB for a DC-DC boost converter only to find that it produced very noisy output. The design is based around the MIC2253. Here's a schematic: Although my circuit allows for ...
20
votes
2answers
5k views

Why are many IR receivers in metal cages?

I'm guessing it's a Faraday cage around the receiver, but don't know why they might need one. Is there some sort of common interference around 38kHz (their operating frequency)? It's the only ...
20
votes
2answers
11k views

FCC part 15 “must accept interference from other sources”: what does this mean?

I've googled around a bit and here are the interpretations I've found in non-authoritative sources: that the device is unable to filter out interference caused by other certified equipment that if ...
17
votes
5answers
7k 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 ...
16
votes
11answers
3k views

Is it possible that the phases of the moon could have an effect on the operation of certain types of electronics?

What type, what could the potential effects be, and why would this happen? EDIT: Yes, I am talking about physics not the supernatural. I figured this would be obvious unless people thought I was ...
16
votes
4answers
9k views

Microcontroller with a long wire for digital input

I have the doorbell button on my house wired into a GHI EMX dev board. The software evaluates the time of day and determines whether or not the doorbell should ring. Side Note: This was ...
16
votes
1answer
326 views

Unusual interference [closed]

I'm experiencing an effect somewhat like GSM frame-rate audio breakthrough in my auditory systems - completely different frequencies but equally wideband. I've noticed it occasionally in the past - ...
14
votes
1answer
3k views

PCB clearance/keepout area surrounding wireless antenna

Suppose a PCB antenna or chip antenna is integrated onto a board design with a wireless IC, e.g. a Zigbee or Bluetooth module. What are some guidelines regarding clearance/keepout area on the PCB ...
13
votes
5answers
8k views

Is it possible to jam wireless home alarm systems?

Sorry if this is the wrong community for this question but in my mind, it's the best fit. Please close or move to a more appropriate community if it's off topic. The other day, several home alarm ...
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 ...
12
votes
6answers
3k views

How to avoid interference in wireless communication?

I am working on wireless communication system. We are using around 10 pairs of transmitter and receivers. We are using atmega16 microcontroller for encoding and decoding by USART ports. Now we are ...
12
votes
4answers
21k views

Wireless Home Automation 2.4GHz versus 433MHz [closed]

Project specifications To make some things clear first(wow that sounds so arrogant): This is an Arduino project This is supposed to be internationally applicable I have experience with 433 MHz ...
11
votes
4answers
2k views

Why is RS-422 interface interference insensitive?

I am trying to understand differences between RS-232 & RS-485. I just don't grasp what is the core principle behind RS-422 inteference resistance? Is it number of wires (4 instead of 3)? Is it ...
11
votes
10answers
6k views

EMI: CFLs vs Incandescent Lights in Your Lab?

Being a green-oriented treehugger, I've put in all CFL lights in my house. Just as much light for about 1/4 or 1/3 the power. Nice, but flourescent lights put out a lot of EMI. Does this cause ...
10
votes
5answers
1k views

What are some quick, cheap hacks for determining the source of EMI in my house?

TL;DR - Without dumping a bunch of money, is there a quick MacGuyver-y way to help diagnose what's causing the EMI in my house? Longer - I have the curse that I'm a little too technical to be helped ...
9
votes
1answer
6k views

What should I know about interference between wires in a multi-conductor cable?

I want to use a multi-conductor cable for a few different circuits. What do I need to know about interference between circuits within a multi-conductor cable? Some of the wires will carry stepper ...
8
votes
1answer
2k views

Killing GSM Buzz with Ferrite Beads

I'm trying to rid my speakers of the typical buzz from my iPhone. I get poor reception in my apartment and so it's constantly trying to find a signal, meaning I get a near-constant buzzing when the ...
8
votes
3answers
1k views

What Regulatory Requirements are Really Necessary for Sale in the USA?

I understand that unless you fall into some specific product categories that are exempt from FCC regulations, electronic products sold in the US are legally required to meet FCC EMC limits. However, ...
8
votes
2answers
3k views

How to build a cheap device to determine where Wi-Fi interference is coming from?

In this post, the ServerFault guys use a fancy tool to map out the WiFi spectrum under normal conditions, with a microwave running, and with a baby monitor on. The baby monitor and microwave cause a ...
7
votes
3answers
5k views

50MHz SPI PCB routing, use vias or resistors?

I am trying to route the SPI between MCU and ADC. However, the pin orders between MCU and ADC are not matched, there are crossings. A four-layer board is used.(signal - ground - power - signal) I ...
7
votes
1answer
10k views

Permanent magnets near wifi device

Background I have a small circuit that consists of a microcontroller operating on 14Mhz and a wifi module. This circuit is enclosed in a small plastic box. I am considering gluing a few magnets on ...
7
votes
3answers
2k views

Sizing an RC snubber

My fridge is sending bad clacks to my loudspeakers when it turns on/off, I fear for the tweeters. I'd add a snubber/suppressor to the compressor but my notions about RC filters from school are 15 ...
7
votes
1answer
493 views

Closing loops or not? - supply lines on a PCB

When routing a Gnd line, I wonder if it's best to keep loops open, like so:   or to close the loop, like so: I could think of some arguments in favor of closing the loop: PRO Looping arguments:...
7
votes
2answers
451 views

What's this noise?

As in other years at precisely this time I'm experiencing an effect somewhat like GSM frame-rate audio breakthrough in my auditory systems - completely different frequencies but equally wideband. I've ...
6
votes
3answers
231 views

Wire to use with Sensors

I am trying to minimize interference in a sensor project. Can anyone recommend a good shielded wire I can solder into my board?
6
votes
1answer
6k views

How do I shield my pc-speakers from mobile interference? [closed]

I have a budget (not cheap :P) pc-speaker set from Logitech (2.1) at home which are extremely sensitive to cellsignal interference. My iPhone is about 1m from any part of the set - including the ...
6
votes
3answers
181 views

What happens to parts of induction cooker magnetic field not covered with the pan?

An induction cooker works like this. There's a flat coil of wire under the cooker surface which is connected to a source of high frequency AC and it produces an oscillating magnetic field with field ...
6
votes
1answer
2k views

GPS consideration for PCB with GSM (interference, setup etc)

I am working on a project which has a GSM and GPS on the same PCB (fairly near each other in an enclosure). Since I am not familiar with GPS I was wondering if any of you could give me some tips on ...
6
votes
1answer
424 views

Help review my first arduino PCB: What did I do wrong? [closed]

EDIT: After taking all what you guys said into account, I edited the pcb into the following. Changed the FTDI while breaking the ground loops and working on the traces a bit, changed the size of the ...
6
votes
1answer
134 views

GPS L5C Differential? Max Update Rate(bits/s|Hz)?

The differential GPS chips use L1 and L2C to calculate the ionospheric interference. With the new GPS satellites, the new band L5C is being deployed, and I am wondering about the following things: ...
5
votes
3answers
7k views

Why do cell phones sometimes interfere with amplifiers

I have an old Sony amplifier (TA-F117R) next to my desk where I keep my cell phone. Sometimes I put it ontop the amplifier, because it is pervecly alighed with the surface. When I hang some call up ...
5
votes
3answers
6k views

Non-metal cases

This question is really aimed at computer cases, but I suppose it also applies to other PCB cases. Most of the Computer cases I come across are aluminium, or else some other metal; As I understand it ...
5
votes
1answer
4k views

Why is an HDMI signal causing interference with Over-The-Air digital television? [closed]

I do not have cable or satellite television so I rely on Over-The-Air digital programming (free) and Internet streaming services to provide entertainment. A couple years ago, I purchased a video card ...
5
votes
2answers
2k views

Why are low frequency channels (10kHz - 200kHz) especially susceptible to interference?

I am working on a system which should communicate with a ~100kHz signal, and read that low frequency channels, e.g 10kHz to 200kHz, are especially susceptible to interference. Why is that? Are they ...
5
votes
3answers
723 views

SPI Bus Routing: Signal Integrity Issue?

I am routing a two-layer PCB with a 10MHz SPI bus. (See picture below.) The device on the left is the 5V master, the device on the right is the 3.3V slave, and the IC in the middle is a 74XX08 quad ...
5
votes
3answers
858 views

Does a twisted pair cable radiate more EM radiation than non-twisted pair?

I am looking at many electronic forums and people always come up with different answers, so I would like to settle this question once and for all. Does a twisted pair cable radiate more EM radiation ...
4
votes
2answers
1k views

Long wires causing Raspberry Pi to die?

I've been working on a simple project involving a Raspberry pi and some switches. I would never thought I would have any problem for something as simple as a switch, but here I am. The 2 wires from ...
4
votes
2answers
6k views

2.4GHz Wi-Fi interference between devices in close proximity, even though they're using completely non-overlapping channels?

Is there any known electromagnetic / interference / [no idea] effect which can cause IEEE 802.11 (Wi-Fi) 2.4GHz devices located in very close proximity (one on top of the other) to severly interfere ...
4
votes
2answers
10k views

How to shield for electromagnetic interference (DIY level)?

I am building an optical rotation encoder for my "autonomous robot" (a LED pointing to a photodiode that gets interrupted as the axis rotates). My issue is that at the voltage that I am using the ...
4
votes
1answer
412 views

Audio oscillator cross-talk on small synth project

I am making a small 9V battery powered synthesizer with a square wave oscillator built around a 40106b Schmitt trigger (reference: http://richdecibels.com/blog/?p=11) and a few other components, one ...
4
votes
2answers
2k views

Guitar picks up computer interference

Years ago I bought a computer case because my other one was getting too small for the components. After moving all of the parts and booting up, one of the first things I noticed was that my guitar ...
4
votes
1answer
796 views

Multiple nrf24l01, shared power, ripple/interference, DSO screenshot provided

I've got this circuit with 3x atmega328 & nrf24l01+ running off shared power supply, either 2x AA battery or 3v3 reg. It acts as a repeater, and depending on the origin of the message and the ...
3
votes
7answers
2k views

Will this PCB trace GSM antenna be affected by EMI?

I am designing a PCB in which there are 3 SIM800 GSM modules sharing a (commercial) external antenna. The external antenna is connected to the PCB via an antenna connector, and from that connector, ...
3
votes
4answers
450 views

Dealing with signal noise over 50 foot communication link

Situation: Connecting a motor controller to an MCU. Motor controller is about 50 feet away from MCU. Connected via a single conduit (buried), containing the following cables: (There is no other ...
3
votes
1answer
611 views

Transformer vs capacitive vs both coupling to speaker

I have seen various configurations in my lifetime on how an 8-ohm output speaker is connected to amplifier circuits. Currently I'm doing a project using an LM386 amplifier and I capacitor coupled ...
3
votes
4answers
736 views

Humbucker-style microphone interference cancelling

For a recent experiment, I decided that it would be a good idea to try to add some electric guitar distortion effects to my otherwise Classical flute playing. In order to do this, I attached a small ...
3
votes
2answers
654 views

Verifying design that uses guard ring

I had a colleague design a board for pH sensor amplification based on schematic (fig 1)and spec in a paper. The paper recommends using the spec noted in figure 3. It uses a guard ring to reduce ...
3
votes
1answer
6k views

Why do library book detectors make my headphones buzz?

Whenever I enter or exit a library while wearing headphones (cheaper intra-aural type), I hear loud buzzing as I pass through the book detector gate. I can vaguely speculate at a high level that there'...

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