Modulation Techniques Projecton

‘Audio Signal Tracer’

Submitted By:

Prashant Kumar

Pradyumn Pasari

Shashi Anand

Shivarth Sharma

AIM

To construct an audio signal tracer useful for troubleshooting audio signals.

OBJECTIVETo design an audio signal tracer that detects any audio signal (20Hz – 20KHz) in a given random circuit and thus to easily detect the portion of large circuit from where the signal is not transmitting further.

Components required1.100k potentiometer

2. resistors 47k- 2 nos

10k- 1 no

1M- 2 nos

3. capacitors 10uF- 3 nos

0.1uF- 1 no

220uF- 1 no

4. operational amplifier – ic uA741

5. speaker – 8 ohms

6. complementary pair of transistors – AC187 and AC188

SOFTWARE USEDMultisim 10

SCHEMATIC DIAGRAM

SIMULATION RESULT

C110uF

C210uF

C3

100nFC4

10uF

R1

1MΩ

R2

1MΩ

R3

10kΩ

R44.7kΩ

R54.7kΩ

R6

100kΩKey=A 50%

2

4 3

1

XFG1

VCC12V

VCC

VEE-12V

6

XSC1

A B

Ext Trig+

+

_

_ + _

0

5

VEE

U1

UA741CD

3

2

4

7

6

51

Q1

BC547BP

Q2

BC557AP

8

C5

220uF10

U2

BUZZER30000 Hz

0

7

HARDWARE IMPLEMENTATION

The above circuit diagram was assembled using all the components listed above in which input signal is applied across the 100k potentiometer and if the input signal is in audio frequency range the speaker starts to beep.

EXPLANATION

A signal tracer is a piece of electronic test equipment used to troubleshoot radio and other electronic circuitry.

Usually a very simple device, it normally provides an amplifier, and a loudspeaker, often battery-powered and packaged into a small, hand-held test probe. An optional diode detector is usually also provided, allowing the detection of amplitude-modulated signals.

The technician injects a test signal into the device under test. Then, by using the signal tracer, the tech can follow the signal through the various circuits of the radio receiver. So long as the signal can be heard, the circuitry up to that point is (at least minimally) functional. If the signal disappears, however, a fault can be assumed to be present in the stage of the circuit just passed.

The diode detector is only sensitive to amplitude modulation but even circuits that are normally used for other modulation schemes (such as FM radios) can be tested by using an AM test signal for testing the radio frequency circuits, then switching to an FM test signal (and switching out the diode detector) for testing the audio circuits of the radio.

More sophisticated signal tracers may display digital levels using, for example, LEDs. For long pulse trains, a cyclic redundancy check may be calculated and displayed, giving the tech insight into the content of circuits that are switching rapidly.

The input signal which is connected to the circuit (possibly though a probe) connected to a 100k potentiometer, which acts as a volume control device.

The signal is then amplified with the help of an IC741. The amplified output is then given to a complementary Class B amplifier to drive the speaker. The negative feedback from the common emitter junction of the two transistor stabilizes the gain of the circuit. The resulting audio output is sufficient to serve as a signal tracer.

REFERANCESwww.wikipedia.com/signaltracer

www.circuitstoday.com/audiosignal/tracer

TEAM MEMBER LIST

Name Registration no. Email ID

Prashant Kumar 09bec303 vit.prashant@gmail.com

Pradyumn Pasari 09bec302 pradyumnpasari123@gmail.com

Shashi Anand 09bec312 shashi.anand91@gmail.com

Shivarth Sharma 09bec313 shivarth.09@gmail.com