Page 772 - Mechatronics with Experiments

758 MECHATRONICS
1 kHz or 10 kHz. Then set the duty cycle (pulse width) of the signal to the following
percentages: 0, 25, 50, 75, 100%. Record the V (t) and V CE on the dual-channel oscil-
in
loscope. Discuss your results. Discuss the following condition: if the output circuit of
the transistor was connected to an electromechanical actuator’s amplification circuit,
what would be the voltage in the output circuit? Assume the actuator and amplifi-
cation circuit combined have a bandwidth of 100 Hz. Simulate this condition using
®
®
Simulink or MATLAB . What is the main advantage and disadvantage of PWM
base signal control versus linear base signal control?

11.3 EXPERIMENT 3: PASSIVE FIRST-ORDER RC FILTERS.
LOW PASS FILTER AND HIGH PASS FILTER

Objectives

1. Understanding the theory of filter circuits and their applications.
2. Circuit design of a passive low pass filter. Build and test the complete circuit.
3. Circuit design of a passive high pass filter. Build and test the complete circuit.
4. Getting familiar with standard measurement tools and signal generators. Measure the
input and output voltage signals of the filter circuit and confirm the expectations with
measurements.

Components

Item Quantity Part No. Supplier
Resistor as calculated 1 81832 Jameco Electronics (www.jameco.com)
Capacitor as calculated 1 130232 Jameco Electronics (www.jameco.com)
Breadboard 1 20722 Jameco Electronics (www.jameco.com)
Set of connection wires 1 set 20079 Jameco Electronics (www.jameco.com)

Theory

Filters are used to “filter” the frequency content of the input signal and present the“filtered”
or “cleaned-up” version of the input signal as its output signal. Low pass filters pass the low
frequency content and remove (more accurately “attenuate” or reduce) the high frequency
content of the input signal. High pass filters do the opposite: remove (filter-out, more
accurately “attenuate” or reduce) the low frequency content and pass the high frequency
content. Band pass filters pass the frequency content in a specific frequency range, and
remove the frequency content below and above that range. Notch filters do the opposite:
pass all frequency content except a selected range which is removed.
In this experiment, we will build and test a passive low pass filter and a passive high
pass filter. The filters will be built using passive components: a resistor and a capacitor.
Figure 11.7 shows the circuit diagram for a low pass and a high pass passive filter.
The input–output voltage relationship for the low pass filter can be derived as follows.
The voltage across the capacitor is the output voltage and is related to the current and
capacitance value as (assuming zero initial voltage at t = 0, V (0) = 0.0),
o
t
1
V (t) = i( )d (11.39)
o
C ∫ 0
1
V (s) = i(s) (11.40)
o
Cs