ARDUINO Projects

• RF audio

  So I have an old project with nrf24l01 module which sending audio by radio frequency over 100 meters using the RF24 audio library which you can download it from GitHub and you can convert the example to make an intercom device or Walkie Talkie or sound system and so on, the only problem of this project it's MONO not STEREO so two Arduinos one for the lift channel and the second to the right channel.
  However the sound quality it's not that nice but after filtering the signal with a resistor and capacitor it's work nicely despite there is a very small amount of noise but I say it's OK so let's jump in the project.
  

  Demonstration

  First, you set up the sender and the receiver.
  

  Sender

  Connect the audio input to A0 (analog input) pin of the Arduino with an electro capacitor to filter the signal I have used a 1000uf 16 volt to get good quality.
  Then the Vcc of the nrf24l01 to 3.3v if you have an external power supply that can deliver 3.3v that will be better than power output pin of Arduino because sometimes it's can only 3v which that not enough to operate the model.
  Pin CE of nrf24l01 to digital pin 7.
  Pin CSN of nrf24l01 to digital pin 8.
  Pin SCK of nrf24l01 to digital pin 13.
  Pin MOSI of nrf24l01 to digital pin 11.
  Pin MISO of nrf24l01 to digital pin 12.
  At the end of the sender set up, you should have the contact like the photo below
  
  
  
  

  receiver

  You need the following thing to make that work.

  • an Arduino nano or uno
  • nrf24l01 to reset the signal
  • speaker 8 ohm 0.5 watt because it's work with 5 volt
  • an amplifier, in this case, I have used PAM8403
  • two resistors 10k ohm, 15k ohm
  • two capacitors, 0.1uf and the second 0.047uf

  connect the nrf24l01 to Arduino like the sender before.
  so the output of the audio is the pins number 9 and 10 the PWM output pins, if you connected directly to the amplifier then you will rarely hear something because of the noise that generates from the PWM signal that not design to drive a speaker only it's work with a tone not a sound like a song or voice.
  I had connected the project with audio output jack on my laptop and I hook up my oscilloscope to the output of the reserve but without the resistor-capacitor filter and this signal form has been shown in my oscilloscope.
  
  
  

  This another photo of the first not so clear

  
  
  
  that signal not working with a voice even 50%, you need an AC voltage to drive a speaker so my solution is to add a 10k ohm resistor on the output pin number 9 and capacitor 0.1uf to ground and 15k ohm to pin 10 with 0.047uf also to ground that work for me 90% and the signal shown in my oscilloscope like the photo below.
  
  
  
  
  when I directly connect it to speaker the sound was so clear but so low I have added an amplifier that works like magic high sound and clear, but only for one channel "MONO" but it's accepted for my wireless intercom project.
  

  Receiver pin connection