Lab Exercise: PWM for D/A Conversion & DC Motor Control in ECE 341, Fall 2005, Lab Reports of Electrical and Electronics Engineering

Download Lab Exercise: PWM for D/A Conversion & DC Motor Control in ECE 341, Fall 2005 and more Lab Reports Electrical and Electronics Engineering in PDF only on Docsity! 1 ECE 341 Fall 2005 Lab Exercise #8 I. Overview In this exercise you will explore issues associated with using pulse width modulation (PWM) to perform digital to analog conversion (DAC). This is the second step in closed loop control of dynamic system. The DAC converts binary values into electrical signals that are discrete in amplitude and time. A DAC is commonly used with some type of energy conversion actuator such as a servomotor, solenoid, or light. The transformation of computer-controlled variables to an electro-mechanical device is what allows computers to control their environment. II. Expectations You will characterize the open loop speed control characteristics of a DC motor using PWM to vary the voltage on the motor and the ADC monitoring the tachometer signal to monitor the motor speed.. III. Objectives 1. Develop a task control flow diagram that models your program. 2. Manage multiple background tasks in an interrupt driven system 3. Send real time data to the LCD. 4. Capture a PWM waveform on the oscilloscope. IV. Process (Same as Lab 1) 1. Determine the requirements for the functionality of the program from the functional requirements. 2. Determine the resources needed to implement the functionality. 3. Modularize the problem into a list of simple tasks. 4. Draw a detailed task list flow chart that implements the required tasks. 5. Develop a test plan to validate that the performance requirements are met for each task. The test plan must include test equipment configuration, watch variables monitored, and/or data sent to the terminal window. For more complicated processes, computational models would also be developed for algorithm verification. 6. Develop and validate the code for each task. 7. Integrate the tasks into a system. 8. Document tests of the system software for compliance to functional requirements established in step 1. 9. Report on the results. V. Functional Requirements (20 points) 1. Calibrate the tachometer for 100% speed 2. Set the output to the percentage of full speed indicated in Table I. 3. Sample the “Tach” feedback once each 20ms. 4. Output the average tachometer value to the LCD every 250ms using floating-point notation in the format of “%5.4f” in percent of full speed.