Questions tagged [interference]

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

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24 views

Prevent Reception from an Extended Distance (Beyond Design)

I have a magnetic field that is being induced onto a power line by a transmitter, which is following the length of the power line to the receiver. The receiver communicates via a loosely coupled coil ...
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93 views
+50

Waves on raspberrypi camera feed, Ground loops? electrical interference?

I run a video recorder in a vehicle built on Jetson Nano (Very Similar to raspberry pi). It runs on 5V . The vehicle has a 24V power supply. I power the video recorder with an automotive-grade 24V to ...
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67 views

Fixing power supply interference issue (?)

I am working on a project that involves controlling WS2812B led strips using a Teensy 4.0 microcontroller. I got everything working during the testing phase, but now, after transitioning from ...
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68 views

How to prevent common ground circuits messing with each other

I made an Arduino based 18650 battery tester that has 4 identical circuits that charge and drain. Testing one battery at a time gives one set of results which I deem to be correct but testing more ...
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222 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 ...
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61 views

Radio static caused by windscreen wipers

I was driving past a radio station transmitter of the radio station I was listening to. I turned on my windscreen wipers, which caused a noticeable static to be emitted through the speakers for the ...
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61 views

Experimenting with a Walkie Talkie

This is one weird bizarre thing which I noticed while I was in the electronics lab. I had this Power Supply and a walkie talkie similar to this I have not ventured in RF side yet. The power supply ...
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1answer
36 views

How to conclude the nature of interference for such scenarios?

This is abit a hypothetical question. Imagine a signal chain where a AC-DC power supply is powering a transducer and the transducer output is coupled to a data acquisition input by a BNC cable. Or I ...
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33 views

Touchscreen keeps failing to communicate with raspberry pi, except when I touch the INT pin

I bought a display with a i2c touchscreen from Aliexpress and hooked it up to my Raspberry Pi 3b+. The screen part works fine, however, the touchscreen part is flaky. When I just boot the pi, the ...
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3answers
186 views

2.4GHz WiFi module causing interference on 433MHz RF receiver module

I have a prototype board which has two RF modules on it, a 2.4GHz Wifi module (ESP-01) and a low cost 433.92MHz RF receiver module (Wenshing RWS-371F-6). My 433MHz transmitter (a remote control) sends ...
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23 views

Can these SPICE models be used to compare single ended versus 4-20mA current signals?

I want to compare the environmental or common mode interference effect to current vs voltage signals by using two different transducer types current and voltage respectively. Below I compare two ...
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1answer
37 views

PCB with 5 Pluggable RF modules and 1 LTE puggable module - will it cause issues for reception at different antennas?

I am designing a prototype PCB which shall have 5 pluggable RF modules and one 4G LTE module as shown in the image The Base board size shall be 240 x 140 mm, RF board size is 40 x 50 mm and LTE board ...
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5k 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 ...
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27 views

Voltage variation and electrical fields Maxwell Equations

I actually know without knowing the reason or the mathematical expression of the physical phenomenon, that if we apply accross a capacitor a voltage which varies in function of the time, it produces ...
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37 views

Hall effect current sensor and proximity to EMI

I am preparing to layout a PCB. I have an ACS723, that I want to use to sense the current going through a relay. In addition to the relay I have a Meanwell IRM-12-20 to supply ac to dc voltage to the ...
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1answer
59 views

DC brush motor EMI

What kind of frequency does a DC brush motor generate? There are a few explanations online as to what causes EMI in DC brush motors (commutator sparking for example) and how to reduce it, but no ...
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34 views

How far does a PCB antenna need to be from a capacitive sensing touch button?

From my basic understanding, capacitive touch works by having a small voltage applied to a touch plane on a PCB, resulting in a uniform electrostatic field. When a conductor (human finger) touches the ...
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1answer
83 views

Can two Radar motion sensor, running next to each other, result a false detection?

I have two CDM324 Radar motion sensors. I want to run the two sensors close to each other. The transmitted frequency is roughly 24 GHz and I am afraid that a small shift in one sensor transmitted ...
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3answers
165 views

I2C noise from 433MHz transmitter

I have built a little thermostat based on BMP280 temperature sensor over I2C, ESP8266 Lolin v3 and STX882 433Mhz transmitter. I have not added additional pull-up resistors or decoupling capacitors. ...
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1answer
44 views

Calculating Capacitance / Rolloff Frequency for Across the Line RFI Supression

I’m in the process of restoring my first All American Five (AA5) tube radio – in this case, a GE Model 115 from the late 1940s. As I’m getting ready to order replacement capacitors for it, one of ...
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1answer
66 views

ADC signal close to D+/D- signals layout suggestion

My circuit is laid out in way so that the analog front end is on a different pcb than the MCU board. The two PCBs are connected with a vertical connector of which 4 pins are used to transfer two low ...
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2answers
74 views

What's the suitable wire size for 9VDC @25 Amps line?

I am trying to put together the requirements for a cable and I was wondering what would be the most suitable wire size to load the DUT with 25Amps @ 9VDC. I will have few other high current lines ...
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92 views

bluetooth 5 interference from other phones interrupts audio (a2dp and hfp)

(I tried to find the best forum to ask this, here seems the best place; please recommend alternative before downvoting) Problem: while listening to music over bluetooth A2DP profile from a gps (zumo ...
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1answer
101 views

When are 1:1 baluns worth it?

I am trying to build an antenna to connect to the GOES-16 satellite (downlink at 1690,1MHz, linear polarization) with my SDR. My plans are using a 1m offset parabolic dish with a BiQuad feed, ...
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1answer
102 views

Can an isoSPI interface work without isolation?

Ive got a LTC6820 that I will be communicating with a LTC6811 and they both use isoSPI but all the example diagrams show the connections going through a transformers and twisted wire like this: But ...
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45 views

How to measure noise on an antenna in system

I am working on an antenna based RF receiver (AM/FM radio) that appears to be picking up interference from other parts of the circuit. I want to view the noise spectrum, but the receiver chip doesn't ...
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1answer
66 views

Where to place RF shield

I'd like to put a pump drive circuit similar to the one shown below on the same PCB that has two I2C devices, a GPS module, seven analog signals, an ESP32 MCU transmitting WiFi via a trace antenna, ...
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1answer
348 views

Brushless motor back and high current and IC

I'm trying to replace the brain of my neato vacuum which is broken. I've already repair a cleaning MOP but with this one I have a problem with the brushless motor which is throwing some party fun in ...
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1answer
84 views

Radar and Standing Waves

I have a doubt about the working principle of a simple Radar. Consider a stationary object, which does not move with respect to our transmitter. We send an electromagnetic wave to it, and it will ...
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1answer
143 views

SPI interfering with ADC sample

I'm attempting to record 8-bit/8kbps audio to an SD card using the samd21g18a microcontroller. I'm having an issue where the ADC sample value drops whenever the SD card is being written to. This ...
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2answers
41 views

Adjacent Signal Selectivity: Section 6.1 of ETSI EN 303 372-2 (RED testing). Bad procedure/standard?

I'm doing pre-certification testing to ETSI EN 303 372-2 V1.1.1 (2016-04), specifically the Adjacent Signal Selectivity test in Section 6.1. I am a Systems engineer with lots of experience designing ...
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1answer
40 views

Unexpected audio signal interference with camera recording

When watching this video I noticed that low audio frequency creates a visual ripple effect. I'd like to know how this is possible. I guess this can't be due to software smoothing of whole-camera ...
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38 views

Two brushless motors mounted together, magnetic interference?

This migth be a bit of an odd question... I got two brushless motors from an old air-board. They are 350 W each and I'm thinking of mounting them together for better torque. But what would happen? ...
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1answer
81 views

Thin CAT6 cable - RFI problems?

I have got a short length (1m) of standard fat CAT5 shielded cable that runs inside a piece of equipment before the signal exits via a bulkhead connector to a PC. It's the old kind that is a real pain ...
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2answers
94 views

MAX 485 performance

I wanted to test the performance of MAX485 drivers. I set up one driver and one receiver 2-3 meters apart. A 100 Hz square wave was being sent down the line. Roughly in the middle of the cable I put a ...
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3answers
81 views

If a PEC surface completely reflects an EM wave, why doesn't an ungrounded shield work?

I was thinking about shielding and its effectiveness. An ungrounded shield doesn't work well for either inductive or capacitive coupling. However, if you think about plane wave theory, a PEC surface ...
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1answer
105 views

Can wax really improve the performance of a FM transmitter?

Why would the use of wax improve the performance of a FM transmitter? Consider this from the video How to build a FM radio transmitter, at 4 min 14 secs: "Theoretically this helps decrease onboard ...
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1answer
83 views

Individual Three Phase Potential Transformers vs Three Potential Transformers in one case

If I had to select between Individual Three Phase Potential Transformers vs Three Potential Transformers in one case for a 600V system (which doesn't require many inches of spacing between phases to ...
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1answer
45 views

Interference from well pump pressure switch and microcontroller

I am using the Parallax Propeller to start and stop timers for an auto racing timing system. Out of 250 cars there were timing issues with about 10 or so. It was very random and hard to diagnose. I ...
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2answers
72 views

Is this quote about interference from wireless charging coils accurate?

This blog post suggests that apple dropped their promised AirPower wireless charging mat because it didn't pass EMI standards, specifically due to the (unconfirmed) idea that they were using a large ...
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32 views

Using a switching DC-DC converter in high dynamic range current/voltage sensing

I'm thinking of making a power meter circuit which will have a high-side current-sensing amp (LTC6102), a resistive voltage divider for sensing the voltage, a dual op-amp (OPA2365) as a buffer for the ...
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85 views

Weird SWD debug port behaviour

Today I have started to encounter strange problems with SWD debugging. The debug only works if I keep my finger on the SWD pins. To be more interesting I have the same problem with the boards I was ...
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4answers
72 views

How is electromagnetic interference possible when measuring voltage difference?

This question is primarily concerned with audio but it's probably applicable to other areas as well. As far as I understand, EMI is caused by electromagnetic waves adding power to wires as they ...
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1answer
65 views

Wireless phone chargers in a lab environment? [closed]

We are talking about devices that are designed to pump out quite a bit of power in the MHz. Admittedly the chips have comms protocols so they don't spew all the time, and the resonant circuits are ...
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140 views

Interference on car bluetooth system

I just did some work on my car audio system and am having some problems with interference. I added a bluetooth receiver and wired it directly to my stereo cd player input. The receiver is powered from ...
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2answers
86 views

Shield grounding location for an STP cable in a balanced system

If a balanced source or driver is coupled to a differential balanced receiver via a balanced STP cable as shown in the hand drawn illustration below: in such case I have read that grounding the ...
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157 views

Grounding the components of a DIY cnc machine

I'm in the process of building a DIY cnc machine. It already runs, but I noticed it has some interference problems (steppers act weird on occasions, the full graphic smart controller LCD has trouble ...
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1answer
63 views

Heaphone amplifier PSU noise

I built myself a headphone amplifier using the LM49600 and a PGA2310 for volume control. This part of the circuit is fairly standard and I don't think it's the problem. I wanted it to be powered by a ...
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1answer
51 views

Standards for conducted EMI testing

I have some doubts to interpret the CISPR standards, one of them is in relation to the test environment for EMI conducted (150kHz up to 30MHz). The minimum size indicated for the vertical or ...
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122 views

How to reduce spike in Power Supply and GND (SCR + Ignition Coil)

My circuit: Signal coupled in power supply (3.3V) of STM32F103 during spark: Is there any benefit to using this diode (circled in red) or not (without this diode the snubber circuit will start ...

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