Download Lab #10: ADC

Lab #10: ADC
SAIT- ENT-DIGI-260
Lab #10: ADC
Edited April 2014
Print pages 3,4 and 5
Objectives:
1.
2.
3.
4.
Build an ADC circuit.
Analyze the operation of an ADC.
Measure the output parameters of an ADC.
Record observations of a functional ADC.
Pre-Lab Preparation:
1. Attend lectures and review the theory of operation of ADCs and related
circuits.
Equipment Required:
1.
2.
3.
4.
5.
6.
7.
Experimenter’s board with 5V power supply
Function Generator
Oscilloscope
Dual Power Supply
PC with access to specification sheets
Parts kit
Misc parts supplied in lab
Additional Notes:
1. Marks will be instantly deducted from your lab if you fail to set the
function generator or supply voltages properly.
2. Use the Experimenter’s board efficiently…the ADC circuit will be
combined with the DAC lab to create an ADC-DAC lab.
3. Wiring neatness is important for this lab. All components must be kept low
to the board as you will keep this circuit on your board until the end of the
semester (trim leads if necessary).
4. You are not permitted to exchange EWB files! Create your own EWB
files.
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Lab #10: ADC
SAIT- ENT-DIGI-260
Procedure 1:
Built, analyze and comment on the operation of an ADC using Electronics
Simulation software.
1. Using Electronics Simulation software, design a functional 8-bit Analog to
Digital converter. See Diagram #1 on the next page.
a.
b.
c.
d.
Use the model for an ADC.
Use 5 Volts as supply voltage and ground as the reference.
Connect a voltmeter to the signal input.
Connect 2 decoded 7-segment displays to the output (one as the
LSD and the other as the MSD).
2. Ensure the diagram is labeled and all the traces are routed neatly. Print
the labeled diagram and include it with your lab submission.
3. Through experimentation and analysis predict the hexadecimal output of
the circuit given a specific input voltage.
4. Answer the questions in the worksheet toward the end of the lab.
5. Demonstrate the circuit to the instructor. Proceed to procedure 2.
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Lab #10: ADC
SAIT- ENT-DIGI-260
U5
U4
DCD_HEX
MSB
DCD_HEX
LSB
U1
Vin
D0
D1
D2
D3
D4
D5
D6
Vref+D7
VrefSOC EOC
Vin
2.5 V
V2
5V
ADC
S1
Key = Space
V3
5V
Diagram #1: ADC/DAC wiring diagram
Procedure 2:
Design, build and analyze an ADC circuit using an ADC IC.
1. Configure an ADC from your parts kit. See diagram #2. NOTE: you may
alternately configure the output as 2, 7-segment displays with a CPLD
binary-to-7-segment display decoder.
2. Calculate the value of the LED resistors. Answer the question in the
worksheet.
3. Connect an open jumper to the WR’ and INTR’ jumper.
4. Connect a potentiometer as a voltage divider (top to 5V, bottom to
ground). Connect the output of the potentiometer to the V+ input.
5. Apply power. Momentarily short the WR’ and INTR’ jumper to ground.
6. Take the measurements required to answer the questions in the
worksheet toward the end of the lab. Verify your predicted outputs by
experimentation and demonstrate to the instructor.
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Lab #10: ADC
SAIT- ENT-DIGI-260
7. Answer the remaining questions in the worksheet.
Diagram #2: ADC Configuration, Procedure 2
Procedure 3 (optional):
Use a transducer in an ADC circuit using an ADC IC.
1. Connect a linear transducer to the input of an ADC and observe the output
results. Transducers may include Phidgets® analog sensors for
temperature, pressure, light, etc… . The device should function with a 5
volt supply.
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Lab #10: ADC
SAIT- ENT-DIGI-260
WORKSHEET
Measurements and observations for procedure #1 (simulated ADC)
Predict the hex display when given a Vin voltage
Vin = 2.5 Vdc
Hex Display =__________________________
Vin = 1.5 Vdc
Hex Display = __________________________
Vin = 4.5 Vdc
Hex Display = ___________________________
Vin = 0.5 Vdc
Hex Display =- ___________________________
Vin = 3.0 Vdc
Hex Display = ____________________________
Measurements and observations for procedure 2:
Show all calculations
1. Calculated values for the LED resistors (hint: spec sheet).
2. Input voltage measurements:
a. With a 0000 0000 output:__________
b. With a 1111 1111 output:__________
3. Calculated discrete voltage steps: _________ Volts per LSB increment
4. Calculated Resolution: ________ %
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Lab #10: ADC
SAIT- ENT-DIGI-260
5. Predict the input voltage to display the number 1A (show calculations).
Measure the circuit’s input voltage to display the value 1A. Record in the
table below:
Predicted VIN for 1A output
Measured VIN for 1A output
VMIN
VMIN
VMAX
VMAX
Do the measured values fall within an acceptable range of the predicted
values? Explain.
Signatures:
Procedure 1 Circuit: ___________
Procedure 2 Circuit: ___________
Submit:
Worksheets
Labeled diagram from procedure 1
Student Name: _______________________________
Date: __________
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