Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6 002 Circuits and Electronics Spring 2003 Handout S03 059 Lab 4 Audio Playback System Introduction In this lab you will construct test and demonstrate the audio playback system that you designed in Homework 11 The lab consists of two parts pre lab exercises and in lab exercises there are no post lab exercises You should complete the pre lab exercises in your lab notebook before coming to lab Then carry out the in lab exercises on your assigned lab day between May 5 and May 9 After completing the in lab exercises have a TA or LA check your work and sign your lab notebook You may hand in your lab notebook to your TA for grading at that time or any other time before the week of final exams During the in lab exercises you are welcome to work with a partner In this case it is best if one person constructs the clock and digital to analog converter while the other person constructs the low pass filter and power amplifier These blocks can be constructed on separate protoboards Signal and ground connections may then be made between protoboards to complete the construction of the audio playback system The point of working with a partner is to speed up construction but not to miss out on testing all four blocks If you do work with a partner make sure to participate in testing the two blocks constructed by your partner so that you see how they work Pre Lab Exercises 4 1 Copy your design for the clock from Problem 1 of Homework 11 into your lab notebook Label all resistor and capacitor names and values 4 2 Next to your design for the clock copy the graph from Part E of Problem 1 of Homework 11 into your lab notebook You will use this information to determine whether the clock you construct during In Lab Exercise 4 2 works correctly 4 3 Copy your design for the digital to analog converter from Problem 2 of Homework 11 into your lab notebook Label all resistor names and values 4 4 Next to your design for the digital to analog converter make a table showing the expected converter output vDAC when each of the data bit input voltages is 5 V and the others are all 0 V Base the table on the actual resistor values used in your design Also note the expected value of the offset voltage vOFF required to center the converter You will use this information to determine whether the converter you construct during In Lab Exercise 4 4 works correctly 4 5 Copy your design for the low pass filter from Problem 3 of Homework 11 into your lab notebook Label all resistor and capacitor names and values 4 6 Next to your design for the low pass filter copy the graph from Part F of Problem 3 of Homework 11 into your lab notebook Also make a table showing the expected magnitude and phase of the filter output vLPF given a 2 V peak to peak sinusoidal input with a frequency of 4 kHz 8 kHz and 16 kHz Base the table on the actual resistor and capacitor values used in your design You will use this information to determine whether the filter you construct during In Lab Exercise 4 6 works correctly 4 7 Copy your design for the power amplifier from Problem 4 of Homework 11 into your lab notebook Label all resistor and capacitor names and values Include the modification which provides for a variable gain of 1 to 5 4 8 Next to your design for the power amplifier make a table showing the expected magnitude and phase of the power amplifier output vOUT given a 2 V peak to peak sinusoidal input with a frequency of 10 Hz 100 Hz and 1 kHz Base the table on the actual resistor and capacitor values used in your design You will use this information to determine whether the amplifier you construct during In Lab Exercise 4 8 works correctly In lab Exercises The in lab exercises involve constructing and testing the individual functional blocks of the audio playback system and then demonstrating the operation of the system as a whole Before you begin to work on the in lab exercises you must obtain from the Instrument Desk in the Lab a plug in board with the counter and memory and a piezo electric speaker The 74HC14 CMOS inverter chip needed for constructing the clock can be found in your lab kit You must return the board and the speaker or headphones after you finish this lab There are a limited number of parts and other students will need them The in lab exercises are organized so that you will construct and test one functional block at a time As each block is found to work properly you will connect it to those which already work Consequently you will alternately construct and test various parts of the audio playback system As you develop the system in this manner it is essential that you turn off the power to the protoboard before you make modifications to your system or begin any new construction Also check your wiring carefully before turning the power back on This will avoid damaging the components in the system and save you considerable debugging time Finally construct the functional blocks as compactly and neatly as possible In this spirit you should find it easiest to use the components to wire themselves together rather than using extra wires This will save you considerable construction time as well as considerable debugging time 4 1 To minimize wiring in this lab the counter and memory have already been assembled on a printed circuit board On the back of this board are pins that will plug into the protoboards in the Lab Plug these pins into the protoboards so that each pin is inserted into a separate protoboard row Further locate the board so that there is considerable protoboard space on the side with the memory output data bits This will make connection to the board easiest For example locating the board towards the lower left corner of the protoboard may prove best The clock can then be constructed above the board while the digital to analog converter the low pass filter and the power amplifier can be constructed to the right of the board Figure 1 shows the pin assignments for the printed circuit board The pins for the eight memory output data bits are on the right hand side The pins for power and ground and the clock input to the counter are on the left hand side You should connect the power pin to the 5 V power supply on the protoboard and the ground pin to ground on the protoboard There are also four counter and memory control pins which must be connected to the 5 V power supply and ground as shown in Figure 1 4 2 Following your
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