thechangelab.com

You Built It?!

Far and few are those times when, another site features something of direct relevance to thechangelab.

/. has this on their “AskSlashdot”

What’s the Coolest Thing You’ve Ever Built?

Aside from the usual humour, there are a few interesting posts.

tompaulco writes:

When I was about 11 or 12, I helped my dad build a Z80 based computer. As far as what I have done one my own (although the article had three people), all of my early exploits were software based. When I was around 13 I wrote the entire game of Monolopoly on a TRS-80. A few years later, since I couldn’t afford Tetris, but I had seen how it worked, I wrote Tetris on my very early PC.

IversenX writes:

As a freshman in the danish “gymnasium” (which is senior year of high school + 2 years of college), we had an project in physics class where we could write about anything we wanted to. As a group of three students we chose to write about digital logic. In the beginning, we only planned to write about digital logic theory, circuit design theory, and so on, but we soon realized we wanted to build an actual circuit design.

After spending days or even weeks designing the thing, we finally had our ÃœberMachine – we called it the DALO (Digital Arithmetic and Logic Unit). It was essentially an ALU with support for addition, subtraction, logic “or”, logic “and”, and logic “not”.

Now, in this day and age of computers, it would take most programmers just a few minutes to make such a program in most programming languages. But this was done entirely in hardware, with no fancy integrated circuits! We used about 15 simple chips (classic phillips 74xx-series), which only contains or, and, not and the occasional full-adder.

For the input, we used manual flip-switches, connected directly to the input legs on the microchips.

For output we used a series of LEDs to output each of the 4 digits in the A-input, B-input and the result. At the same time, we used a classic 7-segment display for each, driven by a 7-segment-decoder chip.

In the end, the things actually worked, which was quite amazing to see. We hadn’t received any formal training in digital logic, electronics, or circuit design – and yet it worked. The entire machine was soldered with more wires than I ever wish to see again, and it took a lot of blood, sweat and… time – but we did it!

Some years later, I was employed as a teaching assistant at the university. One of my classes were in machine architecture, a course which most students couldn’t see as relating to reality very much, because they didn’t believe anybody except large companies could build computers or circuits. On the day of my last class, just a few days prior to the exam, I brought our high school project with me, and showed them how it was built. Several of them were amazed by it, and it really seemed to make a difference. Computers were no longer magical devices crafted by dwarven builders, they were simply complex machines, free for anybody to build.

How about you? What’s the coolest thing you ever built and/or designed? Or did you have an interesiting disaster story? If it’s the latter, then you might want to check this out too.
- toshiya