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I'm not sure if this is the property community to ask this in, but it's the best I could find. I'm new to this kind of stuff, so please excuse me if this question is a little stupid.

I currently have a Raspberry Pi that sends rf remote codes to turn on and off outlets over 433 Mhz, so a 433 Mhz transmitter and a receiver are currently hooked up to my pi, and I use ninjablocks' 433Utils command-line tool to send and receive the codes with no problems:

pi@pi:~ $ /var/www/rfoutlet/RFSniffer &
[1] 1761
pi@pi:~ $ /var/www/rfoutlet/codesend 123456 -l 180
Sending Code: 123456. PIN: 0. Pulse Length: 180
Received 123456
Received pulse 188
pi@pi:~ $

Now, I am working on another project where I would like to send and receive codes betweens PIs, and I happen to have a 315 Mhz transmitter and receiver lying around that I would like to use. To do a little proof of concept, I simply swapped them out with the 433 Mhz one on the breadboard I am using (although the connections are a little different):

433 Mhz: 1

315 Mhz: 2

As you may or may not be able to see from the photos, for both transmitters I have the pins labeled GND, VCC, and DATA connected to the same spot, and for the receivers, I did a simple swap since the pins are laid out the same. (One thing to note is that the 433 Mhz transmitter has an antenna pin, unlike the 315 Mhz transmitter).

For some reason, when I run the same command to send and receive a code, I get no output:

pi@pi:~ $ /var/www/rfoutlet/RFSniffer &
[1] 1732
pi@pi:~ $ /var/www/rfoutlet/codesend 123456 -l 180
Sending Code: 123456. PIN: 0. Pulse Length: 180
pi@pi:~ $

What's going wrong here? I can think of a few different possibilities, but I lack the expertise to figure it out:

  • Do I need to solder a antenna onto the transmitter and/or receiver?
  • Do I have a conceptual misunderstanding of rf codes, and so what I'm attempting to do only works at 433 Mhz?
  • I notice that the 315 Mhz received says "ATAD" rather than "DATA", like on the 433 Mhz transmitter. Does that mean that I need to invert the signal or something like that (and if so, how?)? I assumed "ATAD" and "DATA" were synonymous when swapping the transmitters.
  • Are the 315 Mhz transmitter and receiver are faulty?

If anyone could help me out, I would much appreciate it. Thanks :)

liam923
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  • i think that if you run the LED blink demo code and connect the transmitter instead of the LED, then the receiver should be getting the signal at its output. you can verify with a voltmeter or with an LED. – jsotola Apr 06 '18 at 02:40
  • regarding antenna: I recommend one, a simple wire (17 cm) does the job here, see https://www.einplatinencomputer.com/raspberry-pi-433-mhz-funksteckdose-schalten/ – Fabian Apr 06 '18 at 08:54
  • @Fabian I tried pressing a wire against the antenna connection to test if that would work, but still nothing happened. – liam923 Apr 06 '18 at 13:32
  • only regarding antenna (not an answer): length and windings are important https://electronics.stackexchange.com/questions/132051/433mhz-quarter-wave-length-antenna-longer-is-better – Fabian Apr 06 '18 at 16:30

1 Answers1

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Note: These modules are indiscriminate and will receive a fair amount of noise. Both the transmitter and receiver work at common frequencies and don’t have IDs. Therefore, a method of filtering this noise and pairing transmitter and receiver will be necessary. The example code below shows such an example for basic operation. Please refer to the example code and links below for ways to accomplish a robust wireless data link. Source: http://www.buildcircuit.com/how-to-use-rf-module-with-arduino/

Hope its helps a little.. Reg.: jan

j.d.
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