Some years ago three young students inquired about a moderately complex project to earn some credits. I happily agreed to supervise them and assigned moderately diffcult tasks, namely, to build from scratch a data acquisition system for slow signals. I suggested to connect some sensors to an Arduino microcontroller and then write a program for the Arduino to interface the measurement values to the control system we use in our lab.
The students were very dedicated and a real joy to work with. They had the Arduino under control within a few hours and had the first sensors reporting their measurement values after the first day. Then they worked out a protocol that is compatible with our EPICS-based control system, and after discussions with our control systems experts and even more debugging, eventually the students had a prototype system working. After cleaning up their project, they had to give a presentation and write a report to earn their well-deserved credits.
I soon realized that there is a clear progression of the information generated by a sensor. The information bubbles upwards through a sequence of microcontrollers and computers that provide data-handling, storage, and online presentation to a seminar presentation, and eventually ends up in a report. Understanding the path the measurement data take appeared like a useful concept to communicate to students. Moreover, I wanted the students to understand the details of the signal chain and how it really works. Therefore, I used the hands-on approach with programming the Arduino that serves as communication glue between the sensor and the control system. This proved benecial for the students’ understanding and was appreciated by them. The abstract concepts thus led to a very concrete realization. In the final stages of the project I coached the students on how to prepare a presentation for a seminar according to some simple guidelines, and eventually put the oral presentation into writing for a report to hand in and receive their credits.
This book is inspired by these students and their projects, but goes a step further and adds a number of additional topics such as signal conditioning, controlling actuators such as switches and motors, as well as control system setup, data storage, and networking. Please note that I cover only basic examples that are boiled down to the bare essentials in order to illustrate the main concepts and to get started quickly. Anyway, the concepts covered should come in handy when working with real-world data-acquisition tasks. I basically follow Mrs. Robinson’s guideline of “help you learn to help yourself” (remember the Simon and Garfunkel song?) and try to fill the toolbox with practical know how. This know how should enable the reader to help herself and pick up datasheets and manuals to adapt the basics from this book to realize far more advanced projects.
The main theme of the book is From Sensor to Report, and that should be the guiding principle of using it in the classroom, either in a student laboratory or as the basis for individual projects.
For a student laboratory I suggest installing the software with some of the more arcane instructions before starting the lab. This comprises turning the Raspi into a router (Section 5.4), installing the MySQL database (Section 5.6.2), and installing EPICS (Section 6.1). The students should focus on the sensors and use the above systems as a background infrastructure. They should, on the other hand, understand the basic operation of the sensors, learn how to interface them to a microcontroller, and move the information to the next level on a different computer. This requires them to write network code, fill an SQL database, prepare the protocol files for EPICS, or present data on a web server. In the lab a knowledgeable supervisor, a “tutor”, should be available to answer questions and guide the students. Using solderless breadboards in the lab enables the students to quickly arrive at a working system on which to base further experiments and try out new ideas.
A suitable scope for student projects, suitable for a single or a group of two students, is to connect a small number of sensors to an Arduino. Then they should be given a target system where they can publish the data. This can be a database, EPICS, MQTT, or a web page. After a prototype system is working, the students should present their system in a seminar and prepare a report.
All code and the corresponding images of the circuits on a breadboard, prepared with Fritzing, are available on this book’s web site at https://www.crcpress.com/9780815393603.
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