The Stopwatch That Took Two All-Nighters

Breadboards, wire-wrap, and parts haggled for at Yongsan market — a logic-design lab, and a stopwatch that came together at sunrise.

A look back — long before any of the tools we argue about now.

In my second year there was a required course simply called Lab — the hands-on version of Logic Design, time spent touching hardware. You wired AND, OR, and NOT gates together and checked whether they worked, on up through flip-flops and PLA/PAL. It was my first experiment on something other than a computer, and a strange delight. The seniors called it ppangpan — literally “bread board” in Korean — and in English it really was a breadboard.

The Breadboard with a Built-in Power Supply

Online now you mostly see slimmed-down versions, but the one in our lab was a hefty thing. Teammates put our heads together, dropped in various chips, and tried whatever the assignment specified — and since it was part of Logic Design, input switches and light-emitting diodes were the whole of input and output; the usual task was testing whether the logic came together, per the book, for a given input.

It took more sharp eyes and handiwork than I’d expected, and the main issue was stripping wire insulation to just the right length — not too long, not too short — and connecting it. Later, out in the working world, that side needed study too, but the analog RLC-circuit worries weren’t ours; the tester tracked only the 0-and-1 states of whether current flowed. When something shorted, the breadboard let out a cheerful “beep,” and what began with giggles turned steadily more irritable as the things we built grew complex.

The Final Project

The end-of-term assignment was to build a stopwatch: two buttons for start and stop, five stored lap times, seven digits down to hundredths of a second. Design together, split up the digits, wire them — should work, and (of course) doesn’t. Connect external power and, with that cheerful sound, a short happens somewhere; leave it too long, unlucky, and the chips you’d scraped together burn out.

With no soldering, wire-wrap became the main skill, and most of the patience lived there. Keeping wires short, using colors for distinct purposes, laying things out so debugging would go easier later — it all took a certain instinct. Debugging meant cutting a line and adding another, so a steady hand mattered. The thing came together over two nights, after ten rounds of patch-and-debug, and I handed in a finished product. Patience and a happy ending — watching the sun come up, I turned it in and went to catch the train home. A warm memory.

Buying Parts at Yongsan

There was a Yongsan Electronics Market that looked nothing like today’s, and I wandered it for days buying parts for the final project. The Seonin arcade, I think it was called; you’d just order online now, but back then a wrong turn led you into a computer dealership — the kind of ah, Seoul neighborhood. We’d spread the parts sheet out, note the flip-flops and the rest, dig through bins one by one, group-buy wire and wrapping sockets with friends, and — they were expensive — haggle over the price. Cost optimization was happening too: buy one 74AC374 octal D-type flip-flop instead of four 74AC74 duals, that sort of thing.

P.S. In grad school (1997, 1998) I was the lab TA for this course for two years, so I feel a bit more of a bond with the cohorts a couple of years behind me, and I remember good beer bought on the department budget for the end-of-term party. A few of them became well-known, and I catch news of them now and then — a belated, small wish that it was part of a good memory. One junior, whose name I can’t recall, asked, “I don’t get why we’re doing this drudgery,” and I remember giving the crusty answer that it’s the same question as what use is learning calculus in school. The project I set them was a ping-pong game on an LED array — sorry for assigning something I’d never built myself.

Part of 90s Computer Science Stories — first-person notes on growing up with computers and studying CS in Korea in the 1980s and ’90s. See the full series →

Adapted from my Korean essay on Brunch: brunch.co.kr/@chaesang/52