LAB REPORT-CONTROL SYSTEMS
Abstract
Filters are widely applied in many fields and are found in most of the devices. Such areas include low-pass filters installed in the landline telephones, a high-pass filters that are installed in the DSL modems with high-bandwidth and a band-pass filter installed in the cell-phone. The latter enables one to hear only the person to whom you are speaking, but not any other person around you even if they too are on their calls. Finally is the band-reject filter that helps to reject any AC power signal with a frequency of 50Hz or 60Hz when operating the sensitive appliances. They are also applied in the audio generations, communications, sensors and many others. This lab report analyses the use of both the passive and active filters and their application in the experiment. The report also gives the theoretical analysis and the simulation of the filters into the computerized software in order to determine their influence in the experiment and come up with a graphical representation of their behavior. The objectives of this experiment was to be able to connect the op-amp as a low pass, then as a high pass and finally as a band pass filters and then measure the gain on the output voltage.
The following apparatus were used in the experiment
A set with standard breadboard
A standard instrument suite
741 Op Amp
Resistors with the following range of ohms; 1-100 , 1-10 k , 1-100 k
Capacitors: ~nF
DC voltage supply
Function generator
Oscilloscope
Multi-meter
Connecting wires
Theory and discussion
Every component of a passive circuit such as capacitor, resistor and inductor can be made into complex resistances. In a DC current, there is a constant supply of the voltages. In the case where the circuit has reached its equilibrium, the three components of the passive circuit changes their roles such that the resistor now act as attenuators, the inductors will act as short circuits and the capacitors as the open circuits.
When a variable voltage source is inserted into the circuit, it will change the behavior of the passive circuit. For example, applying a sinusoidal input to the circuit network changes the behavior of the circuit.
A filter
Filters are circuits which are capable of performing functions such as signal processing in order to eliminate the unwanted frequencies in the signals while enhancing the desired ones. Filters are capable of being in different forms. They can either be passive or active, digital or analog, low-pass, high-pass, band-pass, band-stop (a notch for band rejection) or all-pass. Still, filters are either discrete-time or continuous time. Again, they can either be linear or non-linear. Finally, filters are either classified as an infinite impulse response or finite impulse response. Passive filters are made up of the three passive circuit components listed above, while active filters are implemented by combining passive and active devices. Active components are known to amplify the circuit, thus they require an outside source of power to drive them (Irwin, 1996, p.20).
Multisim
This is an advanced simulation device used by engineers, researchers and educators to ensure advanced analysis of the performance of the circuits under operation. It is advantageous in reducing design errors and to shorten the time taken in prototyping. In this way, it saves on the cost of printing and increases the operation life of printed circuit board (PCB) (Horowitz, 1989, p. 50).
Comparison between multisim and the real experiment
Multisim also called electronic workbench, uses a simulation interface, while the real workbench or real experiment has pots and switches that are physically controlled. Again, it is easy to perform mathematical calculations using the real value experiments as compared to the simulated multisim.
Design and results
Filters in the circuit
The electrical circuit was constructed using a 741 Op-amp as shown in figure 1 below. The op-amp had the following component specifications:
R1= 2.2 k, R2= 10 k, C1 = 100 nF and C2 = 220 nF
Figure 1: the filter circuit. Source:( lab 5 manual, n.d.)
The theoretical value of the cut-off frequency was calculated and found to be 60Hz.
Sine waves were then applied to the circuit input voltage and the corresponding output voltage measured. The result obtained was as shown in the table below.
The filters circuit was then simulated in the Multisim, whose main purpose is to regulate the operation of the filter circuit. The results from the experiment with the incorporation of Multisim were as follows.
Multisim in the circuit
The circuit was connected together with the Multisim as shown below
Figure 2: circuit with Multisim. Source: (lab 5 manual, n.d.)
The simulation of the circuit onto the computerized software gave a series of waveforms as shown in the diagram below
Channel A: Vout / Channel B: Vin
Figure 3: circuit simulation. Source: (lab 5 manual, n.d.)
The results obtained from the circuit with Multisim was given as shown in the table below
Summary of experience
The experiment was very interesting to me, especially in the connection of the filter circuit and to see it work perfectly. I learned to integrate filters and Multisim in the circuit. I found simulation process a bit confusing and the graphical a little tricky, but I managed to go through it successfully. The objectives stated for the experiment was successfully achieved, but with few errors due to the reasons stated above.
Time required
The experimental process took 112hours to carry out, while writing of the lab report took approximately 1hour. Thus the total time for the whole exercise was approximately 212hours.
Bibliography
Horowitz, P. 1989. The art of electronics. Cambridge: cambridge university press. p. 50
Irwin, J. D. 1996. Circuit Engineering analysis. Prentice-Hall. p.20
Lab 5 Manual, n.d. Filters using 741 Op-amp
