Four years after building version one of my Word Clock, it had started to die. This was not surprising as, the method I used to drive the LEDs required much higher current than the datasheet says is allowable.
I figured it was time to redesign, with a focus on manufacturability and reliability.
My requirements for version 2 were:
- Electronics should be entirely PCB assembled to make manufacturing easier
- LEDs should be used within spec to ensure longer life
- Mechanical design should be simple and repeatable
- Visually, it must look a product that could be purchased in a store
- Powered by a common USB power supply (Battery supply is not viable due to the amount of current required by the LEDs)
- Can be made for as little money as possible
I started first by designing a 20cm x 20cm PCB with a 9×10 grid of LEDs. This was the optimal layout of words I came up with. Then I chose an LED driver to control the LEDs without needing to use a mess of shift registers and transistors.
The mechanical design was based around layers of laser cut acrylic panels. Then panels would stack together, sandwiching the PCB, and be held together by a decorative bolt.
Based around the version 1 software, the code required little modification. The use of the larger memory of the Attiny841 meant I didn’t have the same low memory restrictions the version 1 had.
Once the basic design was completed, I was able to try a number of new ideas, including a larger round clock face. In addition, I explored different face colours and materials, as well as different LED colours.
Once I have ironed out a few kinks in manufacturing and packaging, the goal is to sell these as a complete product. Watch this space.
EDIT: And we’re live
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