Investigating Analogue and Digital Control during a RET Summer Project
Andrew M. Fawcett
During a summer NSF funded research experiences for teachers project at CMU, participants investigated the electronics components and circuits required for driving and control of a DC motor. An in-service teacher was teamed with a pre-service teacher, an undergraduate electrical engineering student and an electrical engineering faculty member. In this project, emphasis was placed on the use of electronic components accessible to a high school physics lab with the goal of allowing science students to develop an engineering mind set when exposed to analogue and digital electronics concepts.
As a participant on the research experiences for teacher’s (RET) summer program at CMU I was introduced to the Next Generation Science Standards which are structured around three dimensions, scientific and Engineering Practices, Crosscutting Concepts and Disciplinary Core Ideas. What stood out for me straight away was the accent on designing, building and evaluating of devices that serve to solve a defined problem. The NRC framework states that the new standards will “clarify for students the relevance of science, technology, engineering and mathematics (STEM) to everyday life”.1 It was with this in mind that during the RET six week project time in which I was working in a group assigned with the task of driving and control of a DC brushless motor, I reflected on how the project could influence physics instruction at a high school level.
Research Experiences for Teachers Project:
The Research Experiences for Teachers Project is a three year NSF funded project that allows in-service and pre-service teachers to be involved in research in the college of engineering at CMU during a six-week period each year. Participants are placed in groups of four which include a in-service teacher, a pre-service teacher , an undergraduate electrical engineering student and an electrical engineering faculty member. The commonality between the groups is the building or use of smart sensors to solve a defined problem. The project is also supported by the Center for Excellence in Education, who provided pedagogical support and facilitated group dialog during this time.
Control – Learning the Basics:
A control system is any group of components that maintains a desired result or value.2 Control systems are numerous in our lives. Your thermostat in your house is a temperature controller. Similarly a thermostat in the oven regulates the temperature inside. Human beings are also complex control systems. You use your eyes as sensors which give you feedback on how close your hand is to picking up a cup. Based on information from your eyes about proximity and speed, your brain will make a decision on what to do with your hand next. A car might have a cruise control to keep it at a desired speed or a chemical process controlled for quality.
We implemented a systematic approach to understanding control, first looking at manual control and how the position of a toggle switch can influence the voltage applied as an input to a control system component such as a logic gate, digital circuit or DC motor (load).