I had this kitchen scale. It was off. The calibration that is. The spring used for the scaling tension (or what it’s called) had been stressed too much, I guess. Actually seemed steched, or whatever it’s called when it’s a spring.
I like the way the scale looked though. I wanted to use it for something, but what?
A scale is an indicator after all. And while indicators are cool; what do I need to indicate at home?
Well.. I’ve allways had a soft spot for those analog “24-hours” clocks. Those with 24 segments around it’s face, 1 hand and running at half speed of the hour hand on a 12-hour clock.
The way they force one to not focus on the exact time or even just minutes.
So let’s build a clock!
All code, schematics etc is in this git repo (also linked to, at the top under title).
Clocking in So how does one convert a scale to a clock. It should be quite simple. Squeeze a motor in somewhere between the tray and the hand. I might even be able to use the “pushing down” of the tray to activate a button. That should be enough for a working clock.
Materials If I wanted to make a “normal” clock. One with 12 hours. I could probably have used a ready made module. But where’s the fun in that? I tried to run one at half speed, but it wasn’t reliable enough. I don’t know if it was because of my hacking or the quality (or lack thereof) of the module, but the ones I tried ran either too fast or slow. I found a good video about how to use such a clock mechanism as a time reference, though. Do check it out, if you are using that route.
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Well that was quite the break.. I’m back in school for a short time, and don’t have my commute time on the train. But here’s a bit about the code. There will not be invented any wheels here, but i thought I would write a bit about it anyway. I do recommend to read the code in the repo, though. The code is well commented.
First of all. Here is a temporary setup of the hardware collected in the last post.
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Coupling and stands Last time I got the software side of the build together. Now is it time to connect all the hardware more permanently. The most interesting connection is the coupling between the motor and the hand of the weight. The hand gets turned by a rack and pinion mechanism. With the rack connected to the tray (linear motion) and the pinion on the shaft connected to the hand. The pinion was a perfect place to couple the motor onto. (Almost as is it was its purpose..) So I used the gear plugin in freecad1, made one wit same pitch and tooth count2 as the one connected to the hand, and cut it out of a cylinder body with a cutout for the motor shaft. The motor had one of those shafts that had been cut on two side (right side in picture below).
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With the electronics and code in place, there’s not much left to do and say. Or so i thought.. It turns out that completely covering black lines on a white background with white spray paint takes a lot of layers. It ended up taking me months before there had been enough dry days where I was home, and day the paint could dry before the face plate was ready for the facility.
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