Lab #10: ADC SAIT- ENT-DIGI-260

Lab #10: ADC

Edited April 2014

Objectives:

  1. Build an ADC circuit.
  2. Analyze the operation of anADC.
  3. Measure the output parameters of an ADC.
  4. 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. Experimenter’s board with 5V power supply
  2. Function Generator
  3. Oscilloscope
  4. Dual Power Supply
  5. PC with access to specification sheets
  6. Parts kit
  7. 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 labto 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.

Procedure 1:

Built, analyze and comment on the operation of an ADCusing Electronics Simulation software.

1.Using Electronics Simulation software, design a functional 8-bit Analog to Digital converter.See Diagram #1 on the next page.

  1. Use the model for an ADC.
  2. Use 5 Volts as supply voltage and ground as the reference.
  3. Connect a voltmeter to the signal input.
  4. 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.

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.

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.

WORKSHEET

Measurements and observations for procedure #1 (simulated ADC)

Predict the hex display when given a Vin voltage

Vin = 2.5 VdcHex Display =______

Vin = 1.5 VdcHex Display = ______

Vin = 4.5 Vdc Hex Display = ______

Vin = 0.5 VdcHex Display =- ______

Vin = 3.0 VdcHex Display = ______

Measurements and observations for procedure 2:

Show all calculations

1.Calculated values for the LED resistors (hint: spec sheet).

2.Input voltage measurements:

  1. With a 0000 0000 output:______
  1. With a 1111 1111 output:______

3.Calculated discrete voltage steps: ______Volts per LSB increment

4.Calculated Resolution: ______%

  1. 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 / VMAX / VMIN / 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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