andies
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Noise with 433MHz receiver [Completely solved]

Sat Oct 29, 2016 5:52 pm

I am trying to recode a 433MHz signal (two: garage door opener and roller shutter/opener). I bought a simple chinese Model: MX-FS-03V and installed RFSniffer as well as piscope (using pigpiod). I cannot decode any signal because there is too much noise. RFSniffer does not output anything. Therefore, I added two 100muF and two condensators (following https://dmohankumar.wordpress.com/2015/ ... n-note-13/) and still have without pressing any buttons on the sender the picture below
Bildschirmfoto 2016-10-29 um 19.41.59.png
Bildschirmfoto 2016-10-29 um 19.41.59.png (8.58 KiB) Viewed 10003 times
Since I am living in the countryside I suspect that to be noise, in particular because RFSniffer does not output anything (without and with lamda/4 antenne attached to the receiver).

Does anybody has an idea what is going on here? I tried this on a RPi3 with jessie (newest version) and RPi2 with wheezy.
Last edited by andies on Fri Jan 13, 2017 5:42 pm, edited 6 times in total.
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andies
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 6:41 pm

OK, I managed to kill much of the noise using a 1kOhm (between Data and GRD). But now I have a constant high
HighSignal.png
HighSignal.png (11.89 KiB) Viewed 9970 times
and putting my sender about 1cm close to the receiver gives nothing.
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joan
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 7:18 pm

Have you tried http://abyz.co.uk/rpi/pigpio/examples.html#pdif2__433D ?

It should be a lot better at rejecting noise (and use a lot less CPU).

Get rid of the resistor.

andies
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 7:32 pm

Yes, I tried that - to no avail. My problem seems to be that there is a constant HIGH on data (or too much noise) and in particular nothing if I press the button of my sender.
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joan
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 7:40 pm

Have you removed the resistor?

Could you capture a few milliseconds of the received data and show the piscope display?

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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 7:44 pm

The picture above was without the resistor (entire length is 1000ms, as in the default piscope setup). The picture below (my second post) was with resistor.
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 7:47 pm

(Maybe the receiver is broken?)
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 7:58 pm

I'd get rid of any signal conditioning (capacitors and resistors) so we can see the actual signal - noise and all.

A fob message will be about 40 ms long (see http://abyz.co.uk/videos/433MHz.webm to get some idea).

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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 8:01 pm

Thanks for your patience. Here is the raw signal without any resistors or capacitors.
rawsignal.png
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joan
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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 8:18 pm

Okay, there may be a signal there.

Try filtering out short edges to see if it can be cleaned up.

Try pigs fg 17 150 from the command line. Increase the 150 figure to filter more aggressively.

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Re: Noise with 433MHz receiver

Sat Oct 29, 2016 8:32 pm

I just crashed my Pi. Uhmpfg. It will take some time ;-(
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Re: Noise with 433MHz receiver

Sun Oct 30, 2016 7:29 am

I think I have fooled myself: My RPi has rpimonitor installed. This uses port 8888 that is also occupied by PiGPIO. Both seem to interact and this stoped my RPi.

I have now deinstalled rpimonitor. Everything is fine besides I only get a constant high on GPIO 27, no noise nor any signal. Maybe it was rpimonitor that produced the "noise"? And also it seems that the receiver is broken? I have ordered two new receivers and can check in a few weeks.
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Re: Noise with 433MHz receiver

Sun Nov 13, 2016 9:25 pm

OK, the new receiver arrived ("433Mhz Superheterodyne Wireless Receiver RXB8 3.3V-5.5V Steady for Arduino/AVR"). I also set up a competely new RPi3, just to be sure that nothing is disturbing. Unfortunately, I have no reaction if I

Code: Select all

./_433D -r2
with GPIO 2 (PIN 27 according to https://www.raspberrypi.org/documentati ... nd-raspi2/). Now that I have checked two receivers and in fact two raspberries I am more or less finished. Any idea anyone?

(No RPi-Monitor installed.)
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Re: Noise with 433MHz receiver

Sun Nov 13, 2016 9:55 pm

andies wrote: GPIO 2 (PIN 27 according to https://www.raspberrypi.org/documentati ... nd-raspi2/)
GPIO2 is not on pin 27 according to my reading of the link. It should be on pin 3. See also http://pinout.xyz
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joan
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Re: Noise with 433MHz receiver

Sun Nov 13, 2016 9:58 pm

GPIO 2 is connected to pin 3. Pin 27 is connected to GPIO 0.

Do you have an aerial attached to the receiver? Are you powering the receiver from 3V3 or 5V? If 5V are you cutting the receiver output to a Pi safe 3V3? Have you connected the receiver ground to a Pi ground?

A photo of your set-up will be useful.

You could use piscope to confirm you are using the correct GPIO. Connect it to ground and then to 3V3 at you should see the signal on piscope.

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Re: Noise with 433MHz receiver

Sun Nov 13, 2016 10:14 pm

joan wrote:GPIO 2 is connected to pin 3. Pin 27 is connected to GPIO 0.
Sorry for the misunderstanding. I connected Data to
Physical pin 13 / BCM pin 27 / Wiring Pi pin 2.
joan wrote:Do you have an aerial attached to the receiver?
No, but the distance is <1cm.
joan wrote:Are you powering the receiver from 3V3 or 5V?
5 V.
joan wrote:If 5V are you cutting the receiver output to a Pi safe 3V3?
No. Is this necessary?
joan wrote: Have you connected the receiver ground to a Pi ground?
Yes, I did. And: Thank you all!

Attached are two pictures of the setup.
Attachments
IMG_7225.jpg
The setup
IMG_7225.jpg (47.12 KiB) Viewed 9362 times
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Re: Noise with 433MHz receiver

Sun Nov 13, 2016 10:17 pm

IMG_7226.jpg
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next foto
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Re: Noise with 433MHz receiver

Sun Nov 13, 2016 10:37 pm

I can't make out the connections at the Pi end. I'll assume they are GPIO 25, 5V and ground.

If you power the receiver from 5V it is likely to output 5V on its output (unless the datasheet says otherwise). 5V frd into a Pi GPIO can damage the GPIO and the Pi. It is safest to use a pair of resistors as a voltage divider to drop the 5V to a Pi safe 3V3.

I can't see anything wrong with your set-up. Are you sure the transmitter is working?

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Re: Noise with 433MHz receiver

Mon Nov 14, 2016 5:23 am

I will use the other GPIOs to check (I am using GPIO 27 currently). If one GPIO is destroyed, are the other still working?

This is the third receiver I am using.
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Re: Noise with 433MHz receiver

Mon Nov 14, 2016 8:45 am

andies wrote:I will use the other GPIOs to check (I am using GPIO 27 currently). If one GPIO is destroyed, are the other still working?

This is the third receiver I am using.
I doubt the GPIO is destroyed. Because something can happen doesn't mean it will.

I'm not sure if I have already pointed to a test, http://abyz.co.uk/rpi/pigpio/faq.html#H ... ed_my_GPIO

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Re: Noise with 433MHz receiver

Tue Nov 15, 2016 7:21 am

Thank you for the test. Result:

Code: Select all

Skipped non-user gpios: 0 1 28 29 30 31 
Tested user gpios: 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 
Failed user gpios: None
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Re: Noise with 433MHz receiver

Sun Nov 20, 2016 3:41 pm

I have now put a complete new jessie light on my RPi3 with nothing on it except wiringPi: No result. Then I added PiScope (with all the dependencies) and connected the GPIOs with two different receivers. I do not get any result. I have two 433-utils (garage opener and shutters mover) - nothing happens in PiScope.

Does anyone have an idea where I get search for the error? Maybe buying an ardino? I have seen on the web that some people have used exactly the garage opener that I am using and were able to sniff the signal. Why do I see nothing at all?
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Re: Noise with 433MHz receiver

Sun Nov 20, 2016 4:07 pm

andies wrote:I have now put a complete new jessie light on my RPi3 with nothing on it except wiringPi: No result. Then I added PiScope (with all the dependencies) and connected the GPIOs with two different receivers. I do not get any result. I have two 433-utils (garage opener and shutters mover) - nothing happens in PiScope.

Does anyone have an idea where I get search for the error? Maybe buying an ardino? I have seen on the web that some people have used exactly the garage opener that I am using and were able to sniff the signal. Why do I see nothing at all?
I have no ideas. I'd expect the receiver to pick up a signal even if it's just static. I do have a 16 cm aerial soldered to my receivers and transmitters though.

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Re: Noise with 433MHz receiver

Sun Nov 20, 2016 4:28 pm

Noise could be coming from many sources - Wireless Sensor on Central Heating, Harmonic from cell phone, even the processor on a PC, If you have other wireless devices try switching them off and seeing if the signal goes away. Some old BT adaptors also cause the problem as do some routers
Not saying this is the cause but you can't be certain.
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Re: Noise with 433MHz receiver

Sun Nov 20, 2016 4:40 pm

UK_Ham wrote:Noise could be coming from many sources - Wireless Sensor on Central Heating, Harmonic from cell phone, even the processor on a PC, If you have other wireless devices try switching them off and seeing if the signal goes away. Some old BT adaptors also cause the problem as do some routers
Not saying this is the cause but you can't be certain.
The problem isn't noise per se, it's the absence of any signal, even noise.

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