Wireless Interface RF Modules

The Theory
           The theory section will describe in more detail the flow of data from one end to the other, as well as take a closer look at how we can 'tune' the receiver module so that it receives the data more clearly. I don't want to describe how the RF modules themselves work as that would require a seperate tutorial. The modules rank at a moderate level on the complexity scale and as with any analog/rf electronics, there's a lot to know before you can really understand how they work.

Data Flow

           The transmitter/receiver data flow will be one way and start with the 18F452 PIC sending USART ascii data to the Transmitter. The transmitter converts the data into a wireless 434 MHz signal and sends it out the antenna. The receiver sees this signal through its antenna, demodualtes and amplifies it. The receiving PIC is passed the corrected signal and can see that it is USART ascii data.

Tuning The RF Receiver
   Green Is Transmitted Signal   |   Yellow Is Received Signal

           When you first connect the rf transmitter module and rf receiver they might not work because the received signal is very noisey. If you turn the RF coil with a small screwdriver it will change the properties of the receiver to be more like the transmitter.

If you use an oscilloscope like the pictures above you will be able to clearly see any noise on the signal and turn the RF coil until the noise disappears. The red circles indicate unwanted noise on the line, which are cleared away by turning the coil.