DC Motor Control
Recommended for grades 9–14.
Introduction
Small DC motors find many uses in electronic devices and are a favorite component of engineers and hobbyists. The input voltage to a motor determines how fast it rotates, but in many projects it is important to be able to measure the speed of the motor. A tachometer is an instrument that measures the rotational speed of a motor's shaft in revolutions per minute (rpm). Tachometers are used on cars and aircraft to show the rate of rotation of the engine's crankshaft, and can be used to assist the driver in selecting the appropriate throttle and gear settings for safe driving conditions since exceeding the maximum safe operating speed on an engine can lead to overheating and engine failure. Some tachometers use lasers to measure rotational speed; others use a small generator to produce a voltage that is roughly proportional to the rotational speed. This Project uses a Photogate to determine the speed of the motor.
Objectives
In this Project, you will build a tachometer to measure the rotational speed of a DC motor. First you must build a circuit to power your motor from the Vernier Digital Control Unit (DCU). Your circuit should contain a potentiometer to allow the user to control the voltage to the motor. Then you will write a LabVIEW program to determine the rotational speed in revolutions per minute (rpm) by measuring the period of a propeller mounted to the motor shaft passing through a Vernier Photogate.
Sensors and Equipment
This project requires each of the following Vernier sensors and equipment (unless otherwise noted):
Additional Requirements
You will also need a SensorDAQ interface and LabVIEW software for data acquisition.
Download Experiment Preview
The student-version preview includes:
- Step-by-step instructions for computer-based data collection
- List of materials and equipment
The preview does not include essential teacher information, safety tips, or sample data. We strongly recommend that you purchase the book for classroom use.
Standards Correlations
No standards correlations for this experiment.
Experiment 5 from Engineering Projects with NI LabVIEW and Vernier Lab Book
Included in the Lab Book
Vernier lab books include a CD with word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.