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A project log for Tired Clock

A clock that is very tired, hands hanging down. Until someone approaches it

Michael MöllerMichael Möller 10/22/2021 at 22:000 Comments

Idea

It started with me bouncing ideas about my other clocks with an artist that is into "confrontation with machines doing their own thing". Thus, at the next exhibition - in two weeks time - I am graciously allowed to add one exhibit.

Outwards it looks like the clock is nonfunctional, both hands hanging straight down (which is impossible on a normal clock) At random minute intervals, the clock hands slowly and erratically manage to move up to their correct position, and hold it there for a moment,  shiver and then fall back down. Additionally, a distance sensor triggers the display sequence on person approaching.

Internally it is simply two steppers driving each hand, via some simple mechanics, an Arduino orchestrating this and a clockchip for timing.

The challenge is the short time, and the software to make the movements seem like the clock makes an effort to get the hands into position. Otherwise, piece of cake, right?

Gathering parts

Time is short, but I know I have the parts lying around in my workshop. Found two stepper motors in the box with leftover/salvaged motors, fortunatly they are the bipolar type, so no complicated driver chips needed, so a pair of ULN2001 I have in plenty from other projects should do.

Arduino: check, DS1307 chip: check (but SMD?!), prototype shield for Arduino that fortunatly has a SMD area. Clock face ... hmmm ... repurpose from the Jumbleclock.

Also two 3D printed plastic far left; quick prototype/test of the gear and mount of the steppers for moving the clock hands

MISSING: A distance sensor. I think I have one somewhere, but if I do not find it soon, I'll have to buy one. Let's hope it is next-day-delivery available.

Assembly

First soldered the SMD DS1307 on the prototype area and a buttoncell holder. Get the pinheaders and a few wires. I think I'll test the clockchip before the next.

Hmmm... it allows me to set the time, but doesn't keep running when unplugged. After a some software twiddling I seemed to have not "started" the clockchip correct. Now it seems to be working.

Onwards to mounting the ULN2001 and drive steppers.

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