The Next Project – PropClock Reboot!

Last two weeks I have been thinking about what my next project should be, and then this got me thinking about why I keep working on these projects in the first place?

Thinking back, I started most of my electronic projects because I could easily apply the things I learn and see the results firsthand. One day I get an idea, and then I really want to try and see if it would actually work. Most of my projects build up on the work I have done and the things I have learned in past projects.

Some projects like the MSYNC and the Music and Lights system surprised me by working better than I expected. Then there are a few that worked but not quite as well as I expected them to. One of those projects is the Keychain propeller clock (the PropClock). If it’s not obvious by the name what it does then this photo will explain it pretty well.

The PropClock V1 displays the time when it is spun
The PropClock V1 displays the time when it is spinning

And the actual device looks like this,

The PropClock has 7 LEDs  arranged in a row. The case is made from an excel mint can.
The PropClock has 7 LEDs arranged in a row. The case is made from an excel mint can.

Even though from the photo it looks like it is working perfectly, it has many issues. The time doesn’t always show up in the same location. Also the case tumbles when spinning so the LEDs are not guaranteed to face the same direction in every rotation. It is also bulky and heavy to carry around in a pocket. Fixing these problems requires major design changes and so it kind of fell into the bottom of the stack.

This is my original design, but not my original idea. When I was making my desktop propeller clock (pictured in the background of this webpage) I stumbled upon the website of Jussi Angesleva & Stephen Hughes, who used a PIC microcontroller in their original keychain propeller clock (called “Spin”). I used an Arduino Micro for my design without much thinking and this turned out to be a major mistake.

The Micro needs +5 V to operate fully and this means I had to include a voltage booster to increase the voltage of the rechargeable Li-Poly battery from 3.7 V to 5 V. Although smaller than a regular Arduino board, the Micro board was the major constraint for the overall size of the device. Also when not displaying time, the Micro board still consumes a significant amount of power, making this device very inefficient.

Another source of problem was the accelerometer (MMA8452Q) I used to detect the rotation speed of the device and to orient the clock display. The accelerometer output was fairly good when detecting static orientation, but when the device is spinning I had no way to see the exact output from the accelerometer. Hence I was not able to figure out how to accurately detect a rotation using the accelerometer.

By this point you may have guessed what my next project is going to be! Yes, the next project is completing the PropClock and designing it to fix all the problems I ran into last time. To make sure I don’t make the same mistake twice I will set up a proper project plan, project scope, goals requirements, tests and validation procedures and a timeline before I begin. Before getting too deep into this project I am going to write a project proposal and do a feasibility study to come up with an initial design solution.

In related news, I have successfully assembled the Attiny85 programmer board I got from ASIMOWALK5, and will be using it to do a series of tests to see if the Attiny85 would be a suitable MCU for the PropClock project.

Thanks for reading, and stay tuned for more!

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