Electronics
Module 3 – Practical Coursework
The aim of my project is to create a sound distortion circuit for the amplifier of an electric guitar.
To research for a project I chose the internet for my research. I will browse through websites in order to search for the material needed for a project the sites use to find my project was:
- http://users.chariot.net.au/~gmarts/index.html
For my chosen project I will have to perform a minimum of two investigation of research[JI3]. For my chosen project I will research the pin-out diagram for the 4011 NAND gate chip. The Source I used to discover this was the catalogue ‘Rapid Electronics’
I also need to research the pin-out diagram of the 741 op-amp.
Specification
The specifications of the circuit to be constructed are:
· For the circuit to distort the input signals the circuit must have operational amplifiers[JI4]
· The voltage range for the power supply will be 0V to 9V[JI5]
· The voltage range for the inverted power supply for the operational amplifier will be -9V to 0V
· The voltage range for the non-inverted power supply for the operational amplifier will be 0V to 9V[JI6]
Generation of Possible Solutions[JI7]
I now have to deciding on the final circuit diagram. Here are the possible solutions.
1.
The circuit is not complicated
to construct and stands to the chose for the project. However the circuit only
consists of only 2 active devices; the project requires 3 as a minimum. 
2.
The circuit diagram to this
circuit are displayed is two sub-systems, with both of them are able to be
created for the project; however the circuit diagram looks complex[JI8]. The circuit also meets the needs of the course as it contains
three active devices. 
3. This circuit is the probable one to assemble; it meets the needs by containing three active devices. This circuit is the circuit I am going to construct in my project.
Sub-System[JI9]s Development
To construct the circuit I will develop it in sub-systems.
The diagram shows the circuit with the sub-systems outlined.
Key
------- Sub-system 1, a voltage follower
------- Sub-system 2, a filter
------- Sub-system 3, a filter
------- Sub-system 4, not gate astable circuit
Current calculation – I will perform a current calculation on the not gate astable[JI10] sub-system
Þ V = IR
Þ I = V/R
Þ I = 6.46/220K
Þ I = 29.36 mA
The system is designed to distort an
input signal. The signal is first inputted into the circuit at this point the
input wave is at the first sub-system which is the voltage follower which
consists of an operational-amplifier. It is used as a buffer amplifier and has
very large input impedance and low output impedance. So although it has a
voltage gain of 1, it does have considerable current and power gain and can
very effectively isolate a source from a load.
From this the current has now
increased thus the power is also increased by an amount and the impedance has
lowed. The input signal is now at the second sub-system a low pass filter;
which attenuates high frequencies, and allows low frequencies to pass through
without much attenuation. Output of the input signal will now be lowed if the
frequency is high.
The final sub-system is a NAND gate
astable circuit. The output of this sub-system does not have a stable output
state. The output instead oscillates between two voltages levels. Due to the
filter attenuating the high frequencies the input signal is now distorted and
the peaks and troughs of the wave will be cut of, this is called clipping.
Measuring
the frequency
|
Frequency = |
1 |
= |
1 |
= |
1 |
|
|
T |
(2 x
10-3 x 6.5) |
0.013 |
Component
Layout
This
is a diagram of the system layout on the prototype board.
Key
------- Sub-system 1, a voltage follower
------- Sub-system 2, a filter
------- Sub-system 3, a filter
------- Sub-system 4, not gate astable circuit[JI15]
Testing
On the
complete system I will test:
·
The power output of the circuit
·
The output voltages
·
The frequency output of the complete circuit
·
The frequency output of the 3rd
sub-system
Testing the power output of the circuit
|
Power
= IV = |
V2 |
= I2R |
|
|
R |
|
|
|
|
|
|
Power
= IV = 7.32V x 2.71 x 10-3 = 0.01984 Watts = 19.84 x 10-3
|
||
Testing the output voltages [JI16]– A
multi-meter was set as a voltmeter on the 20V range; this was then connected in
parallel with the power supply to give the reading of the input voltage to the
circuit. A second multi-meter with the exact configuration was connected across
the output of the system to read the output voltage. The results were:
This
measurement shows that the voltage output of the circuit do not exceed the
voltage values of the course requirements using the input voltages stated[JI17] in
the specification.
Testing the output frequency of the complete
circuit – The CRO was connected to the output of the
complete system adjacent to the frequency input wave from the signal generator.
The results were as shown:
The
overall gain in the compete circuit is 1.48; the base frequency for system is
77Hz. However the may be a great deal of uncertainty due to the reading of the
CRO.
Testing the frequency output on sub-system 3
a filter – The CRO was connected to the output of the 3rd
sub-system and a frequency wave was inputted into the input. The frequency wave
was produced by a signal generator. The results were as follows:
The
overall gain in the compete circuit is 1.67; the base frequency for system [JI19]was
77Hz. However the may be a great deal of uncertainty due to the reading of the
CRO.
The
complete system is working and fully functional. The system is designed to clip
the peaks and toughs of the wave in order for the sound to distort. This was
achieved.
The
yellow lines indicate the original peaks and toughs before there were clipped.
The red line indicates the clipped wave or the distorted wave.
Limitations
The complete circuit now has been
constructed and a limitation was found. The limitation was that the input
frequency cannot be greater than 7000Hz (7 kHz), as the input frequency follows
through the base frequency which is 77Hz. If the input frequency is too high
the base wave will sound unchanged to the human ear[JI21].
Evaluation
The in the overall system evaluation
on the project it was a success. The input was clipped at the peaks and toughs
of the wave too give a distorted wave. However this was not a straight forward
procedure as problems were encountered. One problem was when it came to
measuring the frequency for the last sub-system. The last sub-system is an
astable circuit; the theory that has been achieved in class came to this equation
for learning the f[JI22]requency
|
Frequency
= |
1 |
|
|
2.2
R C |
A
diagram of the astable circuit studied in theory
A
diagram of the astable in my project
The
problem came deciding on which resistor is to be R, and capacitor is C. Thus I
concluded that the equation could not be applied. So in response to that I read
the frequency off the CRO using the equation:
|
Frequency
= |
1 |
|
|
T |
That
was then calculated to give the answer 77Hz[JI23].
The second problem was only minor.
Once the circuit was constructed it was connected to the power supply in order
to test the circuit. The power supply was on D.C. and the output wave was shape
like a capacitor charging and discharging. This problem was overcome by using
an A.C. power supply to get the clipped wave.
Here
is a diagram of the circuit setup.
Here
is the circuit from a birds eye view.
Repo[JI24]rt
|
23-Feb |
Introduction
to Project Written
aim for project |
|
24-Feb |
Started
Research on project |
|
25-Feb |
Finished
Research Completed
Specification |
|
27-Feb |
Generated
Possible Designs |
|
01-Mar |
Sub-System
design |
|
02-Mar |
Ordered
components from Rapid Electronics |
|
08-Mar |
Components
arrived from Rapid Electronics |
|
09-Mar |
Started
construction on sub-system 4, the astable circuit Started
to write report for the write-up |
|
12-Mar |
Continued
with construction on sub-system 4, the astable circuit Written
report up to date |
|
15-Mar |
Finished
constructing sub-system 4, the astable circuit |
|
16-Mar |
Started
construction on sub system 3, the filter |
|
19-Mar |
Finished
construction on sub-system 3, the filter Started
construction on sub-system 2, the filter Written
report up to date |
|
23-Mar |
Finished
constructing sub-system 2, the filter |
|
26-Mar |
Constructed
Sub-system 1, the voltage follower |
|
02-Apr |
Devised
a testing procedure |
|
09-Apr |
Started
to test the circuit by testing the power output of the entire system |
|
19-Apr |
Continued
with system testing, this time testing the measurement on the output voltages |
|
20-Apr |
Testing
the output frequency of the complete circuit. A signal generator was used in
order to produce the input wave |
|
21-Apr |
The
3rd sub-system was tested using the signal generator to produce a
input wave, the output frequency was noted |
|
26-Apr |
Continued
with writing up project testing |
|
27-Apr |
Finished
writing up project testing |
|
29-Apr |
Continued
with finishing touches to write up |
|
01-May |
|
|
02-May |