Electrical power engineering technology scholar, John McClure works full-time as an electronics design engineer, and in his "spare time" designed and built an arithmetic logic unit (ALU) that holds promise as a teaching aid for engineering technology design courses. His inspiration was a microprocessor architecture course that he took at the University of Houston during the summer of 2015.
Q: What was your motivation for tackling the design of the arithmetic logic unit project?
A: I took the microprocessor architecture course in summer 2015, which is taught by Dr. Moges. He explained how the ALU inside every microprocessor is merely a sophisticated network of simple logic circuits. I was fascinated by the idea and thought building one from simple components would be an interesting experiment. So, I bought several textbooks on the subject. The more I read about how simple transistor circuits combine into complicated computer hardware, the more I wanted to do this project.
At the end of the microprocessor architecture class, students from Dr. Moges' embedded systems class presented their course projects. I then realized that most students did not seem to understand some of the basic hardware or fundamental theory of electronics. I wanted to show students how to create an original electronic design, take it to the next level by designing a real circuit board, and create a professional finished product.
Dr. Moges explained how microprocessor logic works in a way that was very easy for me to understand. He cares about students and it is obvious in his teaching. Hopefully, what I have done has shown how he contributes to the development of every student.
Q: How did you go about building it?
A: I spent a few evenings reading books on microprocessors. Once I decided on the direction, I started doodling the original design on scrap paper, and then re-drew it. Each time I decided on another key detail. I spent another evening choosing which chips, resistors, capacitors, and switches to use in the design. Then I used free software (PCB Artist) to draw a schematic diagram. The schematic is huge - with very fine print it's about 2'x2' - and took two or three evenings to complete. The next step, laying out the printed circuit board (PCB), took another week. I made several false starts before realizing I had to try another technique. I completed the layout in the same software as the schematic. Once the PCB was designed and ordered, I waited about a week to get it from the fabrication facility. I then hand-soldered all the components onto the board over the next few lunch breaks at work.
Q: You have put a lot of work and thought into designing this board. How can it be used?
A: Since a functionally equivalent circuit exists inside every microprocessor, the only application for this device is as an academic training aid. I hope that the students can use it to better understand microprocessor architecture, and build similar devices that interface with it, and someday build an entire computer from scratch.
Q: What advice do you have for students who want to tackle challenging projects?
A: Go for it! If you don't know how to do something, just ask. But, don't be afraid of failure because you'll learn in the process. Set high standards for yourself and try to make your projects look like they were built by a professional. If you have a great idea, but need a little funding, try applying for the Succeed in Engineering Technology Scholarship (SETS). Not only can you get help, you will also meet students and faculty from all technology disciplines who will be eager to help you. Also, I would like to highly recommend the book that explains enough about computer logic for someone to build their own, The Elements of Computing Systems, by Nisan and Schocken.
Q: Describe a typical day in your current job.
A: I am an electronics designer and general electrical problem-solver at an oilfield services company. I absolutely love my job because I get to use my creativity and engineering skills to solve problems. A typical day for me involves working with others to find an innovative approach to a practical problem and using math and science to work out the details of the approach. I source hardware, finalize the design and create assembly documentation. I also do a lot of my own assembly work. Not all of these happen in the same day, of course!
Q: What's next for you?
A: I have a 2-year-old son and another baby due in May. I'll graduate in May as well. I look forward to having more time to spend with my wonderful family once I graduate! As for my career, I hope that my present employer is the right place for me to stay. I really enjoy what I do and the opportunities I have there.