The happiest two weeks of my life

Here is the result of about two weeks’ worth of work.

The year is 1982 in the autumn and all the kids will spend two weeks working somewhere – school is out, it’s called “arbeidsuke”. We are supposed to gain experience from working somewhere. I have discussed working at the local COOP in Tromsø in the audio/video department. This is where they sell the Technics rack that I crave.

Then at the last moment there is a change. Maybe it was the Italian guy called Alessandro who had joined my class, and who had found a place at the Nordlysobservatoriet. He reeked of garlic most of the time, and I think he had curly hair, and he certainly struggled with Norwegian. Suddenly I found myself at the Nordlysobservatoriet in the electronics lab. 3 or 4 guys worked there, and electronics was my great passion, see Til minne om Stein Torp.

As I recall, already on day one I was allowed to play with creating a digital circuit on a Vero board (the one you see above). The integrated circuit was a four-bit counter, and I made it reset itself when it reached a certain value – 10, for instance. With a carry to a second counter it was beginning to look like a clock. Now it would count to 59, and when it hit 60 it would reset itself. This is achieved by using a few AND-gates to detect the number 60 and use the output to reset the counter. So, the value 60 is present at the outputs for a very short time. Not the most elegant solution, but it works.

What I remember, though, is the excitement of going to work every morning with the anticipation of working on my circuit. Piece by piece I added more counters to make a 24-hour clock. I then added a LED-driver integrated circuit which decodes BCD to a standard LED display, and wired it all together. The white ICs on the left contain 7 resistors used to drive the LED. Now I needed a clock pulse, and this comes from a crystal and a counter or two – the result is a 1 HZ signal. It took trial and error to stabilize the crystal, and if I remember correctly a small capacitor in parallel did the trick, probably shorting a higher harmonic to force the crystal to oscillate at its main frequency, the one stamped on the outside. I used a digital analyzer to inspect all the waveforms. Probably Hewlett Packard.

The final steps where a voltage regulator, a transformer, a bridge rectifier, a smoothing capacitor… the regulator IC was a quite expensive one.
The people in the mechanics lab helped me make a metal chassis, and the whole setup was finished before my two weeks were up. I added two push-to-make switches for setting the time.

One day I could not work on the circuit – we drove to the telescope station deep inside Troms, at Skibotn (see this link). That was quite interesting, but I don’ remember much!

The clock still runs all this years later, but I don’t use it anymore.

One thought on “The happiest two weeks of my life

  1. Åsmund March 28, 2022 / 07:07

    Wow! I’m impressed. Must have been fun.

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