FM Transmitter Dec06-01 Client Iowa State University – Senior Design Team
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Transcript of FM Transmitter Dec06-01 Client Iowa State University – Senior Design Team
FM TransmitterFM TransmitterDec06-01
ClientIowa State University – Senior Design
TeamGrant Blythe Luke Erichsen
Tony Hunziker Jacob Sloat
AdvisorsDr. John W. Lamont
Prof. Ralph E. Patterson III
DefinitionsDefinitions FCC: Federal Communication Commission FCC: Federal Communication Commission LCD: liquid crystal displayLCD: liquid crystal display MP3 player: digital music player, (i.e. ipod)MP3 player: digital music player, (i.e. ipod) Satellite radio: subscription radio signal sent via Satellite radio: subscription radio signal sent via
satellite, (i.e. XM radio, Sirius radio)satellite, (i.e. XM radio, Sirius radio) Transmission frequency: The frequency at which Transmission frequency: The frequency at which
the device is transmitting the FM modulated the device is transmitting the FM modulated signal to the FM radio. signal to the FM radio.
Wall wart: AC power transformer designed to plug Wall wart: AC power transformer designed to plug into a standard wall outletinto a standard wall outlet
General Problem StatementGeneral Problem StatementThe objective of this project is to design a The objective of this project is to design a FM transmitter that will:FM transmitter that will:
Connect to a standard headphone output Connect to a standard headphone output jack of an mp3 playerjack of an mp3 player
Transmit a minimum of 12ftTransmit a minimum of 12ft Transmit between frequencies of 88MHz to Transmit between frequencies of 88MHz to
108MHz108MHz Have 4 programmable preset buttonsHave 4 programmable preset buttons Receive power from a cigarette Receive power from a cigarette
lighter/power socketlighter/power socket Automatic on/off functionAutomatic on/off function
General Solution ApproachGeneral Solution Approach The FM transmitter will modulate the signal, send it The FM transmitter will modulate the signal, send it
through an amplifier, and finally through an internal through an amplifier, and finally through an internal antenna. antenna.
General Solution ApproachGeneral Solution Approach
Internal memory will store four programmable station Internal memory will store four programmable station presets from the frequency band. presets from the frequency band.
A LCD screen will display the current transmission A LCD screen will display the current transmission frequency. This LCD will be backlit for easy night use.frequency. This LCD will be backlit for easy night use.
The transmission frequency and presets will be The transmission frequency and presets will be accessible through a button/knob interface that may accessible through a button/knob interface that may also include a lighting system.also include a lighting system.
There will be a microcontroller to access memory, There will be a microcontroller to access memory, automatic turn off/on function, possible lighting, automatic turn off/on function, possible lighting, display frequency, and any other controlling display frequency, and any other controlling concerns. concerns.
Operating EnvironmentOperating EnvironmentThe finished device will operate within a personal The finished device will operate within a personal vehicle or a household room that could be vehicle or a household room that could be exposed to:exposed to:
MoistureMoisture DustDust DirtDirt ImpactsImpacts Reckless negligenceReckless negligence
Intended User(s) / Use(s)Intended User(s) / Use(s)Intended User(s)Intended User(s)
The intended user for this product is anyone The intended user for this product is anyone owning MP3 players or satellite radio devices. It owning MP3 players or satellite radio devices. It does assume the amount of operating knowledge does assume the amount of operating knowledge associated with MP3 player/satellite radio users.associated with MP3 player/satellite radio users.
Intended Use(s)Intended Use(s)
The FM transmitter is intended to make personal The FM transmitter is intended to make personal music players more accessible to listen to music players more accessible to listen to through home and car stereos.through home and car stereos.
AssumptionsAssumptions
The transmitter will be used for all varieties of The transmitter will be used for all varieties of personal music players.personal music players.
The transmitter will be used in a variety of The transmitter will be used in a variety of environments including varying temperatures, environments including varying temperatures, humidity, seismic conditions, and electromagnetic humidity, seismic conditions, and electromagnetic noise.noise.
The transmitter will be used at all hours of the The transmitter will be used at all hours of the day.day.
Similar products will come directly from the Similar products will come directly from the personal music players producers as competition.personal music players producers as competition.
Assumptions Continued…Assumptions Continued…
The device will be used with standard North The device will be used with standard North American FM radio equipment.American FM radio equipment.
The input audio signal will consist of standard The input audio signal will consist of standard music with a frequency range of 20 Hz to 20 kHz.music with a frequency range of 20 Hz to 20 kHz.
The device design will implement solid state The device design will implement solid state electronics.electronics.
The user will have access to a steady power The user will have access to a steady power source able to supply the rated voltage and source able to supply the rated voltage and frequency (if AC) within a 10 percent tolerance.frequency (if AC) within a 10 percent tolerance.
LimitationsLimitations The cost to purchase this product shall not become The cost to purchase this product shall not become
uncompetitive.uncompetitive. The transmitter must conform to FCC regulations.The transmitter must conform to FCC regulations.
– The FCC has regulation broadcast strength of .1kW. The The FCC has regulation broadcast strength of .1kW. The transmitter must not exceed this strength. transmitter must not exceed this strength.
– The device shall conform with FCC rules Part 15 concerning The device shall conform with FCC rules Part 15 concerning unlicensed FM broadcasting. unlicensed FM broadcasting.
– The RF field strength 3 meters from the device should not The RF field strength 3 meters from the device should not exceed 250uV/m.exceed 250uV/m.
The transmission frequency band must stay within 88-The transmission frequency band must stay within 88-108 MHz.108 MHz.
The device shall be capable of obtaining power from The device shall be capable of obtaining power from both a 120 V AC and a 12 V DC source. both a 120 V AC and a 12 V DC source.
Limitations Continued...Limitations Continued... The form of the device must be manageable for ease of The form of the device must be manageable for ease of
transportation and storage.transportation and storage. There must be at least 4 programmable preset There must be at least 4 programmable preset
transmission frequencies.transmission frequencies. The device must transmit at least 12 feet.The device must transmit at least 12 feet. Transmission frequency must be adjustable.Transmission frequency must be adjustable. Transmission frequency must be displayed.Transmission frequency must be displayed. The size shall not exceed 6 in. by 6 in. by 3 in.The size shall not exceed 6 in. by 6 in. by 3 in. The weight shall not exceed 1 lb.The weight shall not exceed 1 lb. The device shall be compatible with both digital and The device shall be compatible with both digital and
analog tuned radios. analog tuned radios.
Expected End-ProductExpected End-Product
The device case will be made of plastic The device case will be made of plastic The case will allow for easy hand manipulation and The case will allow for easy hand manipulation and
transportationtransportation The device will implement an LCD screen The device will implement an LCD screen
displaying the transmission frequency. displaying the transmission frequency. The user input interface will consist of six buttons. The user input interface will consist of six buttons.
– ““up” and a “down” button to adjust transmission up” and a “down” button to adjust transmission frequencyfrequency
– 4 buttons will each access a programmable preset 4 buttons will each access a programmable preset frequencyfrequency
Detailed FunctionalityDetailed Functionality Pushing and releasing a preset button, in less than 3 Pushing and releasing a preset button, in less than 3
seconds, will adjust the transmission frequency to seconds, will adjust the transmission frequency to the stored frequency assigned to that button. the stored frequency assigned to that button.
Pushing and holding a preset button for greater than Pushing and holding a preset button for greater than 3 seconds will assign and store the current 3 seconds will assign and store the current transmission frequency to that preset button.transmission frequency to that preset button.
Both the LCD display screen and the buttons may be Both the LCD display screen and the buttons may be backlit for use in low ambient light environments.backlit for use in low ambient light environments.
This device shall come with an adapter for use with This device shall come with an adapter for use with an American standard wall outlet. This will be a an American standard wall outlet. This will be a simple wall wart device. The output from this simple wall wart device. The output from this adapter will be a male power jack.adapter will be a male power jack.
Detailed Functionality Detailed Functionality Continued…Continued…
The transmitter will also come with an adapter for The transmitter will also come with an adapter for the standard cigarette outlet for automobile use. The the standard cigarette outlet for automobile use. The output of this adapter will be a male power jack.output of this adapter will be a male power jack.
Both adapters will connect to the device through a Both adapters will connect to the device through a common female jack. The adapters will be designed common female jack. The adapters will be designed so that the device will receive the same power input so that the device will receive the same power input regardless of which adapter is being used.regardless of which adapter is being used.
An instruction manual will also be included. An instruction manual will also be included. The device and accessories should be deliverable by The device and accessories should be deliverable by
December 2006.December 2006.
Detailed DesignDetailed DesignThis includes the different systems within the This includes the different systems within the design, the parts currently considered to design, the parts currently considered to implement these systems, and preliminary prices implement these systems, and preliminary prices of these components.of these components.
InputsInputsManual InputsManual Inputs
These inputs allow the user to adjust and fine tune the These inputs allow the user to adjust and fine tune the transmission frequency manually.transmission frequency manually.
There will be two buttons for the manual input function.There will be two buttons for the manual input function.
– one to adjust the transmission frequency up and one one to adjust the transmission frequency up and one button to adjust the transmission frequency down.button to adjust the transmission frequency down.
Adjustment of the transmission frequency will happen in Adjustment of the transmission frequency will happen in increments of 200 kHz. increments of 200 kHz. – For example 102.7 MHz will increase to 102.9 MHz or decrease to For example 102.7 MHz will increase to 102.9 MHz or decrease to
102.5 MHz in response to the received input.102.5 MHz in response to the received input.
Inputs Continued…Inputs Continued…Preset InputsPreset Inputs
The four programmable preset frequencies shall be The four programmable preset frequencies shall be stored in non-volatile memory in the device. stored in non-volatile memory in the device.
The transmission frequency shall be adjusted to any of The transmission frequency shall be adjusted to any of these frequencies by pushing one of the four these frequencies by pushing one of the four corresponding buttons. corresponding buttons.
A preset shall be programmed to the current frequency A preset shall be programmed to the current frequency by pushing and holding the corresponding button for by pushing and holding the corresponding button for greater than 3 seconds. greater than 3 seconds.
These four buttons will be backlit for use in low light These four buttons will be backlit for use in low light environments. environments.
Inputs Continued…Inputs Continued…Power SupplyPower Supply
The device shall receive its power input The device shall receive its power input from a 12 V DC cigarette lighter/power from a 12 V DC cigarette lighter/power socket in an automobile or a standard 120 socket in an automobile or a standard 120 V AC wall outlet. An adapter will be V AC wall outlet. An adapter will be provided for each of these two sources. provided for each of these two sources.
– Both adapters will provide a common 5 V DC Both adapters will provide a common 5 V DC output to the device. output to the device.
– The device will have one power input jack that The device will have one power input jack that will be capable of connecting to either adapter.will be capable of connecting to either adapter.
Inputs Continued…Inputs Continued…Power Supply Continued…Power Supply Continued…
The adapter for the cigarette lighter will be a single The adapter for the cigarette lighter will be a single stage adapter that plugs directly into the standard stage adapter that plugs directly into the standard cigarette lighter/ power outlet of an automobile. cigarette lighter/ power outlet of an automobile. – The adapter will convert the 12V output of the cigarette The adapter will convert the 12V output of the cigarette
lighter to the 5V DC input needed for the devicelighter to the 5V DC input needed for the device The source from the wall outlet will be a wall wartThe source from the wall outlet will be a wall wart
– Converts the 120V AC to a 5V DC output Converts the 120V AC to a 5V DC output – Provided by the EE/CprE Senior Design Provided by the EE/CprE Senior Design
Inputs Continued…Inputs Continued…Input SignalInput Signal The input signal may come from an The input signal may come from an
mp3 player, or a satellite radio mp3 player, or a satellite radio system. system.
The audio signal input is expected to The audio signal input is expected to consist of audio frequencies within consist of audio frequencies within the range of 20Hz to 20 kHz. the range of 20Hz to 20 kHz.
The device shall accept a stereo input The device shall accept a stereo input audio signal through a standard 3.5 audio signal through a standard 3.5 mm stereo jack. mm stereo jack.
ProcessingProcessingMicrocontroller Design RequirementsMicrocontroller Design Requirements
It will take in the manual and preset inputs and tune It will take in the manual and preset inputs and tune the device to a transmission frequency depending on the device to a transmission frequency depending on which buttons are pushed. which buttons are pushed.
It will allow the device to store transmission It will allow the device to store transmission frequencies into the preset buttons. frequencies into the preset buttons.
It will also implement the auto turn on/turn off It will also implement the auto turn on/turn off function with respect to the input signal. function with respect to the input signal.
The LCD display will also be controlled by the The LCD display will also be controlled by the microcontroller. microcontroller.
Processing Continued…Processing Continued…Microcontroller SolutionMicrocontroller Solution
The PIC processor PIC16F873A was chosen along The PIC processor PIC16F873A was chosen along with the LM555 clock. with the LM555 clock. – It contains a 28 pin IO interface and the memory and It contains a 28 pin IO interface and the memory and
processing power needed for our application. processing power needed for our application. – PIC processors will give us the necessary computing power PIC processors will give us the necessary computing power
to control all components of the device including the LCD. to control all components of the device including the LCD. – At the same time PIC processors are inexpensive and will At the same time PIC processors are inexpensive and will
fall within the project budget. fall within the project budget. – PIC processors also possess the non-volatile memory PIC processors also possess the non-volatile memory
necessary to store the preset stations.necessary to store the preset stations.
Processing Continued…Processing Continued…Microcontroller Solution Microcontroller Solution
Continued…Continued…
PIC16F873A Microcontroller
Processing Continued…Processing Continued…Auto On/Off ImplementationAuto On/Off Implementation The microcontroller will be in a continuous loop The microcontroller will be in a continuous loop
awaiting the input in order to control the awaiting the input in order to control the peripherals. peripherals. – Upon detection of an input signal, the device shall power Upon detection of an input signal, the device shall power
on and begin transmitting within 1 second.on and begin transmitting within 1 second.– After detecting no input signal for 1 minute, the device After detecting no input signal for 1 minute, the device
shall power down within 1 second.shall power down within 1 second.– This count down is a period to wait for signal before This count down is a period to wait for signal before
actually powering down. This prevents premature power actually powering down. This prevents premature power down. down.
Modulation/TransmissionModulation/TransmissionModulation/Transmission BlockModulation/Transmission Block
After examining the available technologies, an After examining the available technologies, an integrated solution was found to provide the integrated solution was found to provide the modulation, amplification, and transmission.modulation, amplification, and transmission.
The device will implement a Rohm Electronics The device will implement a Rohm Electronics
BH1415F Wireless Audio Link IC to provide stereo BH1415F Wireless Audio Link IC to provide stereo modulation and FM transmission.modulation and FM transmission.
Modulation/TransmissionModulation/TransmissionRohm BH1415FRohm BH1415F
Modulation/TransmissionModulation/TransmissionRohm BH1415FRohm BH1415F The BH1415F consists of a stereo modulator for The BH1415F consists of a stereo modulator for
generating the stereo composite signal and a FM generating the stereo composite signal and a FM transmitter for broadcasting an FM signal on the air.transmitter for broadcasting an FM signal on the air.
The IC transmits on a frequency range of 88 MHz to The IC transmits on a frequency range of 88 MHz to 108 MHz. The transmission frequency is set by the 108 MHz. The transmission frequency is set by the microcontroller.microcontroller.
Modulation/TransmissionModulation/TransmissionComposite Stereo Composite Stereo SignalSignal
Modulation/TransmissionModulation/TransmissionFM ModulationFM Modulation The composite stereo signal is then modulated The composite stereo signal is then modulated
with a carrier signal. with a carrier signal. – This carrier signal is the frequency you tune to with an This carrier signal is the frequency you tune to with an
FM radio.FM radio.
The carrier signal is set on the BH1415F by the The carrier signal is set on the BH1415F by the microcontroller using a data packet.microcontroller using a data packet.
Modulation/TransmissionModulation/TransmissionData Packet to BH1415FData Packet to BH1415F
Modulation/TransmissionModulation/TransmissionCarrier Frequency DataCarrier Frequency Data
For Example: in the case of 99.7 MHz carrier frequency.For Example: in the case of 99.7 MHz carrier frequency.
99.7 MHz / 100 kHz (fref) = 997 99.7 MHz / 100 kHz (fref) = 997 3E5 (HEX) 3E5 (HEX)
OutputsOutputs
There are two outputs from the device. There are two outputs from the device.
An LCD screen that will display the frequency that An LCD screen that will display the frequency that the device is currently transmitting at. the device is currently transmitting at.
The other output is the FM audio output The other output is the FM audio output transmitted by the antenna.transmitted by the antenna.
Outputs Continued…Outputs Continued…LCD Display RequirementsLCD Display Requirements
When a frequency change occurs, the When a frequency change occurs, the microcontroller will send the appropriate control microcontroller will send the appropriate control signals to the LCD display.signals to the LCD display.
Each of the 4 digits plus the decimal point displayed Each of the 4 digits plus the decimal point displayed will be controlled individually, and will only need to will be controlled individually, and will only need to be refreshed when the frequency is change. be refreshed when the frequency is change.
The format of this display will be “XXX.X” (i.e. The format of this display will be “XXX.X” (i.e. “102.7”). “102.7”).
The display is also backlit.The display is also backlit.
Outputs Continued…Outputs Continued…LCD Display SolutionLCD Display Solution
The LCD chosen was the VIM-404-DP-FC-S-The LCD chosen was the VIM-404-DP-FC-S-HV LCD manufactured by Varitronix. HV LCD manufactured by Varitronix.
It is a transflective backlit displayIt is a transflective backlit display The way it accepts inputs is dependant The way it accepts inputs is dependant
upon its programming making it a upon its programming making it a versatile choice. versatile choice.
Its 20 I/O pin interface is typical for LCD Its 20 I/O pin interface is typical for LCD components on the market. components on the market.
Outputs Continued…Outputs Continued…LCD Display SolutionLCD Display Solution
Outputs Continued…Outputs Continued…LCD Display SolutionLCD Display Solution
PinPin COMCOM11
COMCOM22
COMCOM33
1-31-3 N.C.N.C. N.C.N.C. N.CN.C44 1B1B 1C1C 1P1P55 2B2B 2C2C 2P2P66 3B3B 3C3C 3P3P77 4B4B 4C4C ------88 ------ ------ COMCOM
339-109-10 N.C.N.C. N.C.N.C. N.CN.C…… …… …… ……
Outputs Continued…Outputs Continued…AntennaAntenna
The device will use a small wire antenna that will The device will use a small wire antenna that will remain inside the device case. Because the case remain inside the device case. Because the case is plastic and the transmission range is small, is plastic and the transmission range is small, there should not be a need for an external there should not be a need for an external antenna.antenna.
Overall SchematicOverall Schematic
Unforeseen IssuesUnforeseen IssuesDisplayDisplay Interfacing with microcontrollerInterfacing with microcontroller
Rohm BH1415F Wireless Audio Link IC Rohm BH1415F Wireless Audio Link IC Phase Lock LoopPhase Lock Loop
Questions?Questions?