RF 433. "Noise"

Hi,

Im new to Radio communication with Arduino.

Basically im trying to see the signals my remote switch for wallplugs are sending. I started follow this walkthrough http://arduinobasics.blogspot.se/2014/06/433-mhz-rf-module-with-arduino-tutorial.html.

The problem is when im Reading the analog pin that the 433 receiver is plugged in to i get alot of noise. I have also tried go outside my apartment but still the same result. Is it possible that what i call noise isnt noise at all?

Giving the remote a keypress i can see some sort of a pattern in the output. I have no clue how to get rid/sort out all the "noise".

Spec:
Basic Specification:
Frequency: 433Mhz.
Modulation: ASK
Receiver data output: High - 1/2 Vcc, Low - 0.7v
Transmitor input voltage: 3-12V (high voltage = more transmitting power)
Transmitting range (work at 5V): 40m indoor, and 100m in open air

My code:

#define rfReceivePin A0 //RF Receiver pin = Analog pin 0
#define ledPin 13 //Onboard LED = digital pin 13

unsigned int data = 0;

void setup(){
pinMode(ledPin, OUTPUT);
Serial.begin(9600);
}

void loop(){
data=analogRead(rfReceivePin);
Serial.println(data);
}

The problem is when im Reading the analog pin that the 433 receiver is plugged in to i get alot of noise. I have also tried go outside my apartment but still the same result. Is it possible that what i call noise isnt noise at all?

Yes, that isn't noise. The output of the 433 receiver is NOT analog data.

Its actually the digital equivalent of noise.
The 433 receiver simply converts thermal noise which is present everywhere into a digital equivalent, which simply looks like random transitions between 0 and 1, perfectly normal.

Ok.
How do i determine if something returns analog or digital data?

Whats the different from my RF receiver compare to the one used in the link in my first post?

You have to write a program to distinguish noise from signal. Usually this involves measuring pulse widths. This link is a good place to get started: Interface with Remote Power Sockets – Final Version « RAYSHOBBY.NET

mauried:
Its actually the digital equivalent of noise.
The 433 receiver simply converts thermal noise which is present everywhere into a digital equivalent, which simply looks like random transitions between 0 and 1, perfectly normal.

No necessarily, could be a nearby amateur radio station or even military radar. Both may operate on or near 433 MHz.

Paul

I have seen some examples using a libary called radiohead. I have also tried it...but i cant get any output. Is that due to the "noise"?

I have seen some examples using a libary called radiohead. I have also tried it...but i cant get any output. Is that due to the "noise"?

Probably not. Code and a picture of your setup would be useful. Some explanation of your environment would be useful.

Sorry the libary i have been testing is RCSwitch.

Arduino Setup:

Arduino Uno rev 3

This RF module: http://www.lawicel-shop.se/prod/433Mhz-RF-link-kit_1040722/Seeed-Studio_79829/SWE/SEK

RF Receiver module goes to Digital pin 2.

Code:

/*
Simple example for receiving

*/

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

void setup() {
Serial.begin(9600);
mySwitch.enableReceive(0); // Receiver on inerrupt 0 => that is pin #2
}

void loop() {
if (mySwitch.available()) {

int value = mySwitch.getReceivedValue();

if (value == 0) {
Serial.print(“Unknown encoding”);
} else {
Serial.print("Received “);
Serial.print( mySwitch.getReceivedValue() );
Serial.print(” / ");
Serial.print( mySwitch.getReceivedBitlength() );
Serial.print("bit ");
Serial.print("Protocol: ");
Serial.println( mySwitch.getReceivedProtocol() );
}

mySwitch.resetAvailable();
}
}

Maybe the signal sent by your outlets is not compatible with the RCSwitch library. It CERTAINLY will not be compatible with the RadioHead library.

See reply #4

How many wallplugs is your remote designed to control?
You can figure this out by how many buttons there are on the remote.
The RC switch library is designed to decode the protocol format of the SC2262 / PT2262 data encoders
which are used in many remote wallplugs , but not all.
A good guide is that if the wallplug remote is designed to control up to 4 remote wallplugs, theres a good chance that it will use one of these decoders, otherwise it wont , and you are then in for an interesting exercise in reverse engineering a proprietary protocol.
Another option is to pull the transmitting remote apart and see if you can identify any ICs in it.

Hi
This topic is allready 5 years old, but I feel it is still an actual one.
I recently started with RF 433 modules and had a lot of noise in a simple setup where the receiver was connected to an arduino uno. I tried a pullup, condensor (both on the output) and a supply condensor but nothing worked well enough.
For some reason I took the receiver supply away from the arduino and connected a separated DC/DC converter instead.
From there, my signal is noise free.

My conclusion is, that the noise is produced by the MCU that has an impact on the arduino supply. (And of course, that
receiver is very sensitive).
In this case a software noise reducer will not help, neither will packet repetition. Power supply decoupling however will.

cool

I recently started with RF 433 modules and had a lot of noise in a simple setup where the receiver was connected to an arduino uno.

That is normal behavior and not a problem.

To test the receiver, connect a matching transmitter to another Arduino somewhere nearby, and send a valid signal.

cool53:
My conclusion is, that the noise is produced by the MCU that has an impact on the arduino supply. (And of course, that receiver is very sensitive).

There is an element of truth in that.

It is true that the running CPU can produce enough EMI to affect radios and in general the faster the CPU clock speed the worse the problem. You can for instance see slightly reduced sensitivity of LoRa devices and GPSs from high clock speed CPUs, but then these are running with very low signal levels indeed. Some USB powerbanks radiate very large amount of EMI and I have seen them cause reductions in sensitivty of LoRa devices by 20dBm+.

However the problem is really that the Arduino is as a board producing the EMI, and its next to impossible to stop it being picked up by the radios antenna, unless your receiver is in a screened box.

Good supply decoupling can help a bit, but its by no means the full story.