How to Build a Tiny FM Radio Transmitter With an Arduino for Under $5

Building your own miniature FM radio transmitter using an Arduino is a fun electronics project that can be completed on the cheap. With just a handful of components, you can broadcast your own music or voice over any standard FM radio within about a 50-foot radius.

What You'll Need

To build a tiny FM transmitter with an Arduino, you'll need the following parts:

• Arduino Nano or another small Arduino board - The Nano is perfect for this project thanks to its tiny size. Any Arduino will work though. Cost: Around $4 on Amazon

• 433Mhz or 315Mhz ASK RF Transmitter Module - This module handles the FM transmission. They cost just a few cents. Cost: Around $1 on eBay

• Length of wire - This works as the antenna. You'll want around 20cm of thin insulated wire. Cost: Free if you have some spare wire around

• Breadboard - For easily connecting the components. Cost: Around $5 on Amazon

• Assorted jumper wires - For hooking up the Arduino and transmitter module. Cost: Around $5 for a pack on Amazon

That's it for required components! Optional extras could include a small amplifier or outdoor antenna for increased range. But the parts above are all that's needed to get your micro FM transmitter up and running. The total cost is under $5, assuming you already have an Arduino available.

Circuit Design

The circuit for this DIY FM transmitter is very straightforward.

We simply need to:

• Connect the Arduino to the RF transmitter module so it can feed audio signals to the module.

• Provide power to both components.

• And hook up an antenna to transmit the FM radio waves.

Here is a circuit diagram showing how everything needs to be connected:

We'll use the Arduino's TX pin (pin 1) to feed audio data to the transmitter module's data pin. The Arduino and transmitter module should share a common ground.

A breadboard makes it easy to plug everything together. Jumper wires connect the modules to the Arduino's TX pin and ground pins.

Code

With the circuit wired up, we need to upload code to the Arduino to generate the FM audio signal.

Here are the key steps in the Arduino sketch:

• Import required libraries - Especially the SoftwareSerial library for transmitting data from the TX pin.

• Set up SoftwareSerial - This establishes serial communication on the TX pin to feed data to the transmitter.

• Set transmission frequency - We define the exact frequency we want to broadcast on.

• Generate audio data - In the loop(), analogWrite() generates the mono audio signal. You can plug in your own audio samples or noises here!

• Transmit audio data continuously - The SoftwareSerial object feeds the audio data to the transmitter module.

The full code for the Arduino FM transmitter is available on GitHub. You can tweak the code to modify the broadcast frequency or audio being generated.

Upload the code, and you're ready to broadcast!

Building the Antenna

A wire antenna helps extend the range of the transmission. The antenna should be about 20cm long. Strip both ends of the wire and twist the exposed ends.

Connect one end of the wire to the antenna/ground pins on the transmitter module. The other end can dangle freely. Positioning the antenna vertically will give the best results.

Testing and Using Your DIY Transmitter

Once everything is assembled, give your Arduino FM transmitter a test!

Power on the Arduino, and tune any nearby radio to the frequency specified in your code, such as 107.0 MHz. You should suddenly hear your audio broadcast emitting from the radio's speakers!

The broadcast range is roughly 50 feet for this little DIY transmitter. Outdoors or with an upgraded antenna, you can extend the range. Just stay within legal transmission power limits.

To use your micro FM station long-term, you could:

• Enclose it in a custom radio case for portability.

• Power the Arduino via batteries or a USB charger.

• Add an audio input device like a headphone jack or microphone.

• Replace the default audio in the code with your own sound clips or voice tracks!

So there you have it - with about $5 of parts and some simple Arduino code, you can set up your very own miniature FM radio station for endless DIY broadcasting fun!