Ipod Fm Transmitter

iPod FM Transmitter

Created by: Larissa Duron David Orozco

FM Transmitter - Purpose


Created to stream music from your iPod using an FM stereo in your car or at home.




The sound from the iPod will broadcast through the transmitter and play through an FM frequency.

FM Transmitter & iPod


A FM Transmitter is portable device that uses FM radio waves to send sound from any audio device that contains an auxiliary port or mini jack.




The iPod is a portable media player that plays several audio formats using a flash memory, a touch screen with video capabilities.

FM Transmitter & iPod

FM – Frequency Modulation


The carrier’s amplitude stays constant and its frequency varies according to the amplitude variations of the audio signal.




When the input signal’s amplitude increases the frequency of the carrier increases too.

FM – Frequency Modulation


When the input signal decreases in amplitude the carrier frequency decreases.




The output frequency the transmitter is adjustable from 88 to 108 MHz which is the FM band that is used for radio broadcasting.

FM - Testing


For testing purposes, the circuit was designed in Multisim to assure working ability.




The input frequency (iPod) was defaulted to 100 MHz.

FM – Testing Multisim

In this figure, you can see that the frequency range is at 116.83 MHz which indicates that the circuit works. Adjustments will be made after the calculations for accurate FM broadcasting.

Components





iPod Analog Auxiliary cable (male to male) ¼ copper wire (antenna) LED




Capacitors: C1, C2 = 0.01uF C3 = 10PF C4 = 1uF C5 – 0.33uF C6 = 0.1uF C7 = 100pF (Variable)




IC Regulator = 7806









Resistors: R1 = 27 K ohms R2 = 10 K ohms R3 = 470 ohms R4, R5 = 1 K ohms R6 = 150 ohms

Transistor: Q1 = BC337 Vin = 9V

Components

Purpose of the components


Capacitors - to protect the circuit by storing energy in the electrostatic field.




Voltage regulator - to maintain a constant output from a voltage source even when the load current varies. **The voltage regulator is keeping the voltage constant at 6 volts – 5 volts in Multisim**

Purpose of the components


RF coil - acts as an inductor and stores the energy in a magnetic field and creates a carrier frequency to the variable capacitor.




Variable capacitor - changes the energy from 5% to 100% and works with the RF coil to create a carrier.




Resistors - provide a given opposition to the current flow which is also needed for protection to the current flow.

Schematic

XFC1 123

V2 5V 0

C3

R3

8

C7

470 Ω

10pF 100pF-VAR Key = A

10 5%

XMM1

0 0

0

5

27k Ω R6 150 Ω

C5 0.33uF 0

R1

4

LINE VOLTAGE

COMMON

1

V1 9V

Q1 BC337

L2 SAMPLE_RFCOIL

U2 LM7805CT VREG

0

C6 0.1uF

0 0

C2 0.01uF

C4 1uF C1 0.01uF

3 LED1

0

R2 10k Ω

0

0

0

7 R4 1k Ω

R5 1k Ω

XFG1

0

12

In this figure, 100 MHz frequency was used as the input frequency (iPod).

Calculations for RF coil (Inductance) 5 = 2.5mm 2 N = NumberTurns = 4 B = LengthCoil = .8mm C = Diameter = 5mm A = Avgdiameter =

0.8( NA) 2 0.8(4 ⋅ 2.5mm) 2 induc tan ce = µH = = = 5.3µH 6 A + 9 B + 10C 6(2.5mm) + 9(0.8mm) + 10(5mm)

f R ( MIN ) = f R ( MAX ) =

1 2π L ⋅ C 1 2π L ⋅ C

= =

1 2π 5.3µH ⋅ 100

−12

1 2π 5.3µH ⋅ 10

−12

= 36.2 MHz = 143.5MHz

Calculations with Inductors replacing the RF Coil


Use two 8.2 µH inductors in parallel

1 1 L= + = 4.1µH 8.2 µH 8.2µH 1 1 f R ( MIN ) = = = 78.6MHz −12 2π L ⋅ C 2π 4.1µH ⋅ 100 f R ( MAX ) =

1 2π L ⋅ C

=

1 2π 4.1µH ⋅ 10 −12

= 248.5MHz

Calculations for Antenna λ = wavelength f = 100MHz c = 300,000,000 f =

3 × 10 →λ = = 3m λ 100 MHz 1 = λ × Lantenna = 3m × = 0.75m 4

300,000,000

Lantenna

8

Testing Frequency - Oscilloscope

Conclusion


Music was transmitted from the iPod to the antenna output source of the FM Transmitter to a FM radio station – 90.1 FM.

Pros:
Inexpensive
Simplicity
Portable

Conclusion