Making FM Radio Receiver Using Arduino and Si4703

                        FM Radio Receiver Using Arduino and Si4703

Reference: TeknoTrek in CircuitsArduino

    In this project, we will build a fully functional FM radio receiver using the Arduino Nano and the Si4703 FM tuner module. This easy-to-follow guide is perfect for hobbyists and electronics enthusiasts who want to dive into the world of radio frequency and wireless communication.

    The Si4703 module is a highly integrated FM receiver that simplifies the process of tuning and listening to FM stations. Paired with the Arduino Nano, a rotary encoder, and an LCD display, this project will not only provide you with a working radio but also teach you the basics of RF circuits and Arduino programming.

    By the end of this tutorial, you'll have a clear understanding of how to set up and program an FM radio receiver, tune into your favorite stations, and adjust the volume with just a few components.

What You'll Learn:

1. How to interface the Si4703 FM receiver module with an Arduino.

2. How to use a rotary encoder for frequency tuning.

3. Displaying information on a 16x02 LCD screen.

4. Building a compact and functional FM radio with a stereo amplifier.

5. Let's get started on your journey to building your own custom FM radio receiver!  

                                                      Supplies

1. Arduino Nano (or any compatible Arduino board)

2. Si4703 FM Tuner Module

3. PAM8403 Stereo Amplifier Module (for enhanced audio output)

4. 16x02 LCD Display (to show the frequency and other information)

5. Rotary Encoder (for tuning the frequency)

6. Speaker or Headphones (for audio output)

7. Push Button (for power or station selection)

8. 10k Potentiometer (to adjust the display contrast)

9. Breadboard and Jumper Wires (for easy connections)

10. 5V Power Supply (or USB power for the Arduino)

11. Soldering Tools (if needed for permanent connections)

Optional:

1. Enclosure or Casing (to house your project neatly)

2. Antenna (for better FM signal reception)

Step 1: Schematic

                                              Arduino Fm Radio

    The schematic for this FM radio receiver project is straightforward and easy to follow. It consists of the following key components:

Arduino Nano: The central microcontroller used to interface with the Si4703 FM module and control other components such as the rotary encoder and the LCD display.

Si4703 FM Module: This FM tuner module is connected to the Arduino via the I2C (SDA and SCL) lines. It receives the FM signals and sends the audio data to the amplifier module.

PAM8403 Stereo Amplifier Module: The amplifier boosts the audio signal from the Si4703 and drives the speaker or headphones. It is powered by the same 5V supply as the Arduino.

Rotary Encoder: The rotary encoder is connected to the Arduino to allow for tuning of the FM frequency. Turning the encoder changes the frequency and is displayed on the LCD screen.

16x02 LCD Display: The LCD screen shows the current FM frequency and other information. It is connected to the Arduino using the I2C protocol, sharing the same SDA and SCL lines as the Si4703 module.

Power Supply: The entire circuit is powered by a 5V supply. If a 5V supply is not available, a 7805 voltage regulator can be used to step down from a 12V supply.

    In the schematic, connections are clearly shown between components. The I2C lines (SDA and SCL) are shared between the Si4703 and the LCD. The rotary encoder is connected to digital pins on the Arduino for detecting changes in rotation. The amplifier is powered by the same supply as the Arduino and receives audio signals from the Si4703 module.

Make sure all connections are secure, and follow the schematic carefully to ensure correct functionality.

Step 2: Gather All Components and Set Up the Breadboard

 

    Start by gathering all the required components for the project: Arduino Nano, Si4703 FM module, LCD display, rotary encoder, PAM8403 amplifier, and other parts. Once you have everything, set up the breadboard by placing the components and connecting them according to the schematic. Make sure to organize the wiring neatly to avoid confusion during the assembly.

Step 3: Video Presentation In this section, you'll find a video demonstration of the DIY FM radio project. The video walks you through the assembly process, component connections, and the final testing of the radio. You’ll also see how to tune into different FM stations and adjust the volume using the rotary encoder. Watch the video to gain a better understanding of each step and see the project in action!

Step 4: Arduino Code Use this libraries: GitHub

Step 5: Enjoy! Power up your FM radio using a 5V power supply. If a 5V supply is not available, you can use a 7805 voltage regulator with a 12V input to safely power your radio.

Congratulations on completing the project! I hope you enjoyed building this FM radio and learned something new along the way.

Feel free to share your version of the project, and don't hesitate to ask any questions or share feedback. If you liked this project.

                                 Thanks again for following along!

Voltage Standing Wave Ratio

          When a transmission line (cable) is terminated by an impedance that does not match the characteristic impedance of the transmission line, not all of the power is absorbed by the termination. Part of the power is reflected back down the transmission line. The forward (or incident) signal mixes with the reverse (or reflected) signal to cause a voltage standing wave pattern on the transmission line. The ratio of the maximum to minimum voltage is known as VSWR, or Voltage Standing Wave Ratio.

          A VSWR of 1:1 means that there is no power being reflected back to the source. This is an ideal situation that rarely, if ever, is seen. In the real world, a VSWR of 1.2:1 (or simply 1.2) is considered excellent in most cases. In an EMC lab where many of the tests are very broadband in nature, a VSWR of 2.0 or higher is not uncommon. At a VSWR of 2.0, approximately 10% of the power is reflected back to the source. Not only does a high VSWR mean that power is being wasted, the reflected power can cause problems such as heating cables or causing amplifiers to fold-back.

          There are ways to improve the VSWR of a system. One way is to use impedance matching devices where a change in impedance occurs. Baluns are used extensively in antennas to not only convert from balanced to unbalanced signals but also to match the impedance of the source to the antenna. It is common practice in EMC testing to include attenuators at any point where there is an impedance mismatch. One emissions standard, for instance, specifies using an attenuator at the connector of a biconical antenna since it has a high VSWR at some frequencies. One of the conducted immunity standards suggests using a 6dB pad at the input of the coupling device, which is commonly 150 ohms. Attenuators obviously cause power loss, but they reduce VSWR by providing an apparently better termination to a signal.

          For example, lets look at a 6dB attenuator and its affect on circuit impedance. Following is a schematic for a 50 ohm 6dB attenuator:

          If a 50 ohm termination is added to the output of this attenuator, the source will see a 50 ohm load. Two extremes for terminating a transmission line are open and short circuits. In a completely open circuit, the impedance would be infinite. Adding this 6dB pad to the output of a signal source, without terminating the output of the attenuator, would cause the source to see an 84 ohm termination (17 ohms in series with 67 ohms). Shorting the output of the attenuator would cause the signal source to see a 30.5 ohm termination. In each case, the VSWR would be approximately 1.65:1. (The math will be covered later).

          There are various ways of measuring and/or calculating VSWR. In the old days of open transmission lines, the voltage could be measured along the length of the line until the maximum and minimum values were found (which were ¼ wavelength apart) hence the reference to Voltage Standing Wave Ratio. Thus, VSWR would be calculated by the following formula:

          With the use of coax cables, measuring voltage along the cable is impractical. Dual-directional couplers can be used to measure the forward and reverse power, and these values can then be used to compute VSWR.

          VSWR can also be represented other ways, such as Return Loss, Mismatch Loss and Reflection Coefficient. Reflection Coefficient is common, can be calculated several ways, and ultimately used to calculate VSWR. Here are some formulae for determining Reflection Coefficient (Y):

          Once the reflection coefficient has been calculated, it can be used to determine VSWR by the following formula:

          Another way to describe the affect of VSWR is Return Loss. Return Loss is the measure in dB of the ratio of forward and reverse power. If the return loss is 10dB, then 1/10 of the forward power is reflected back. Return Loss can be calculated by the following formulae:

         Yet another way to reference reflected power is Mismatch Loss (or Transmission Loss). This is a dB ratio between the incident power and the power actually absorbed by the termination. Following are formulae for computing Mismatch Loss:

         For instance, if 100 watts forward power is delivered into a load and 15 watts is reflected, 85 watts is absorbed by the load. This gives a reflection coefficient of 0.387, a VSWR of 2.26, a return loss of 8.2dB and a mismatch loss of 0.7 dB. In other words, the power actually absorbed (or not reflected) by the termination is 0.7 dB less than the forward power delivered to the termination. Keep in mind that the terminating device may have its own internal losses and therefore may not utilize all of the absorbed power in the intended fashion. Such is the case with an antenna that may have some losses associated with its balun.

Where to Measure

          It is important to know that for accurate VSWR measurements of devices, the VSWR should be measured at the input of the device in question (antenna, CDN, etc). Any cable loss, or attenuation, will make the VSWR at the input of the cable appear much better than at the load or termination. The reason is that the cable loss or attenuation increases the return loss.

          For example, (see diagram below) let’s say that there is 3 dB of attenuation along the length of a cable. If we send 100 watts forward power into the cable, only 50 watts makes it to the termination. Let’s say that the termination reflects 30 watts back. When the reflected signal makes it back to the amp, the same 3dB of cable loss will reduce the reflected power to 15 watts. The amp would see a VSWR of 2.26. However, using 50 watts forward power and 30 watts reverse power to calculate VSWR, we end up with a VSWR of 7.9! The amp sees a return loss of 8.2dB, but at the termination the return loss is 2.2dB, or exactly 6dB difference.

          While the cable loss can be added into the measurement, it is more accurate to make the measurement at the input of the device in question. The reason is that every connection or device along the way can have its own VSWR.

          Evaluating a device for VSWR properties should be done in a laboratory with something like a VSWR or impedance bridge, measured at the input of the device. However, in the real world it is not often safe or practical to monitor VSWR at the device input during normal operations.

          Earlier it was mentioned that inserting an attenuator would improve VSWR. Keep in mind that it does not change the VSWR of the terminating device -- that remains constant. However, it does improve the VSWR seen at the other end of the cable. It does this at the expense of wasting power, however. Some amplifiers are not very happy when they see a mismatch in impedance, and may have reduced power output, a distorted waveform, or even be damaged. Using an attenuator may allow continued operation of the amp without fear of damage or shut-down due to the mismatch.

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Various Transmission Media

Transmission Media:

Transmission media is a pathway that carries the information from sender to receiver. We use different types of cables or waves to transmit data. Data is transmitted normally through electrical or electromagnetic signals.

          An electrical signal is in the form of current. An electromagnetic signal is series of electromagnetic energy pulses at various frequencies. These signals can be transmitted through copper wires, optical fibers, atmosphere, water and vacuum Different Medias have different properties like bandwidth, delay, cost and ease of installation and maintenance. Transmission media is also called Communication channel.

Types of Transmission Media:

Transmission media is broadly classified into two groups.

     1. Wired or Guided Media or Bound Transmission Media

     2. Wireless or Unguided Media or Unbound Transmission Media

Wired or Guided Media or Bound Transmission Media:

           Band transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. Popular band transmission media  in use are twisted pair cable, co-axial cable and fiber optical cable. Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc.

Wireless or Unguided Media or Unbound Transmission Media:

          Unbound transmission media are the ways of transmitting data without using any cables. These media are not bounded by physical geography. This type of transmission is called Wireless communication. Nowadays wireless communication is becoming popular. Wireless LANs are being installed in office and college campuses. This transmission uses Microwave, Radio wave, Infra red are some of popular unbound transmission media.

          The data transmission capabilities of various Medias vary differently depending upon the various factors. These factors are:

1. Bandwidth.

          It refers to the data carrying capacity of a channel or medium. Higher bandwidth communication channels support higher data rates.

2. Radiation.

          It refers to the leakage of signal from the medium due to undesirable electrical characteristics of the medium.

3. Noise Absorption.

          It refers to the susceptibility of the media to external electrical noise that can cause distortion of data signal.

4. Attenuation.

          It refers to loss of energy as signal propagates outwards. The amount of energy lost depends on frequency. Radiations and physical characteristics of media contribute to attenuation.