Components of a filter
jontha11
components.docxIn the next section of the lab, you are going to implement a real-time, moving average filter and measure its frequency response, but first, both input antialiasing and output anti-imaging low-pass filters need to be designed, built, and tested to ensure proper operation of the moving average filter.
Please note that both the antialiasing and the anti-imaging filters will be used in all the remaining labs in this course. Construct and test them carefully and do NOT dismantle them after this lab is completed as you will need them for the rest of the session.
The real-time filter will be implemented on the Tower microcontroller system that you already have from the previous microcontroller classes and will include the use of the analog-to-digital (ADC) and digital-to-analog (DAC) converter module board that is part of the total Tower system. However, the ADC will require an antialiasing, low-pass filter to condition its input, and the DAC will require an anti-imaging, low-pass filter to condition its output.
As a result, you are to design and test two identical, active, second-order, Sallen-Key low-pass filters per the following schematic shown in Figure 2.
You may refer to iLab 2 as a reference because this design was simulated there. However, now you are to actually design, build, and test the filters. The antialiasing and the anti-imaging filters may be identical, so once you build and test one, you may duplicate your design for the second. An LM741 op amp is used in the above schematic, so if you choose to use a different op amp, please verify the pinouts and connections prior to building. Please create and include a schematic of the filter design with the lab materials if you’re using a different op amp than the LM741.
The sampling frequency of the software provided for this lab is set at 2.0 kHz. Therefore, the filter specifications for the filters are as follows.
Low-Pass Cutoff (-3 dB) Frequency: 1,000.0 Hz
Pass Band Gain: 1.0 or 0 dB (Unity Gain)
R1 and R2 values should be the same, and C1 and C2 values should be the same. Please note that there are numerous combinations of resistor and capacitor values that could provide the same cutoff frequency calculations, but try to keep the resistor values between 1.0k Ohms and 10.0k Ohms.
Calculate the design values of the resistors and capacitors and record all values in Table 1 in the Week 3 iLab cover report.
Because it is highly likely that you will not be able to find actual resistor and capacitor components that match your calculated values, try to find values as close as possible to the calculated values for use in your circuit construction, and record them in Table 1 in the iLab cover report. If you cannot find close enough values, you will need to redo the design calculations.
Calculate the -3dB frequency from the actual component values used for the circuit. Please keep in mind that all components have a tolerance factor and that your test measurements will reflect this.
Once the filters have been designed and constructed, you are to test and record the frequency response of the filters to ensure their proper operation using a signal generator, power supply, and oscilloscope. The initial settings of the signal generator should be the following.
Frequency = 200 Hz
Vin (p-p) (amplitude) = 2.0 Vpp = 1.414 Vrms,
DC offset = 1 volt
