Want to add wireless capabilities to your next Arduino project, for less than the price of a cup of coffee? Well, then 433MHz RF Transmitter and Receiver Modules are just for you! They can often be obtained online for less than two dollars for a pair, making them one of the most inexpensive data communication options that you can get. And best of all, these modules are super tiny, allowing you to incorporate a wireless interface into almost any project.
Let’s have a closer look at the 433MHz RF Transmitter and Receiver Modules.
This little module is a transmitter among two. It is really simple as it looks. The heart of the module is the SAW resonator which is tuned for 433.xx MHz operation. There is a switching transistor and a few passive components, that’s it.
When a logic HIGH is applied to the DATA input, the oscillator runs producing a constant RF output carrier wave at 433.xx MHz and when the DATA input is taken to logic LOW, the oscillator stops. This technique is known as Amplitude Shift Keying, which we will discuss in detail shortly.
This one is a receiver module. Though it looks complex, it is as simple as the transmitter module. It consists of a RF tuned circuit and a couple of OP Amps to amplify the received carrier wave from the transmitter. The amplified signal is further fed to a PLL (Phase Lock Loop) which enables the decoder to “lock” onto a stream of digital bits which gives better decoded output and noise immunity.
ASK – Amplitude Shift Keying
As discussed above, for sending the digital data over radio, these modules use a technique called Amplitude Shift Keying or ASK. In Amplitude Shift Keying the amplitude (i.e. the level) of the carrier wave (in our case it’s a 433MHz signal) is changed in response to the incoming data signal.
This is very similar to the analog technique of amplitude modulation which you might be familiar with if you’re familiar with AM radio. It’s sometimes called binary amplitude shift keying because there are only two levels we are concerned with. You can think of it as an ON/OFF switch.