Wickenburg High School Math Club Builds Computer

  Under the direction of their math teacher, Richard McKeon, these students had a great time constructing the computer on a 4 x 8 foot sheet of plywood. Not only was this a fun project, but an excellent learning experience in computer architecture and logic. For details of construction and wiring we used the book “How To Build A Working Digital Computer” by Edward Alcosser.

The plywood sheet was sectioned off for the different computer functions:

1.    The drum memory was a piece of stove pipe with several paper clip wipers. The program of instructions consisted of holes cut in a sheet of graph paper that was wrapped around the drum. The drum could be rotated so that one instruction at a time could be read.

2.    Because digital computers use binary logic, we built an encoder section to convert “regular” (base 10) numbers to binary. For this we built our own rotary switches from thread spools wrapped with un-insulated wire. The switches were programmed by wrapping tape around them that had holes cut in appropriate places. The wipers again consisted of bent paper clips.

3.    To get the results of an operation back out of the computer in base 10 numbers we built a decoder section using a series of knife switches and lamps to display the decimal numbers.

4.    For temporary storage while computing the core memory consisted of paper clips bent in such a way that they could store a “1” or a “0” by lighting (or not) a lamp.

5.    To wire up the arithmetic unit we had to understand how a series of knife switches could be arranged to perform binary arithmetic and display the results.