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Designing a case for BicycleCompanion

A project log for BicycleCompanion

A modern, low-power and hackable cycling computer designed for bicycle-touring

Matias N.Matias N. 06/01/2020 at 21:060 Comments

While waiting for parts (already arrived!) and PCBs (to arrive tomorrow) I decided to start designing a case for BicycleCompanion. Initially I intended to do so in OpenSCAD but, while I like the programming-based approach, it lacks certain features that can quickly make a relatively simple model become really complex to develop. I then turned to FreeCAD. I struggled to learn to use it in the past and I gave it a honest attempt, watched tutorials, etc, but the interface is really unintuitive and I couldn't go past a very basic attempt. Finally, I decided to give Fusion360 a try. I don't really like that it is a Windows only, closed-source application but at least they provide a free license for personal/hobby use. Coupled with the free Windows license I get from my University it made sense to try.

Immediately after starting Fusion360 I really liked the interface, it is completely intuitive and well thought. I must say that it took me about three attempts to start doing things right, until I really understood the philosophy behind the tool. Understanding the timeline concept was critical and once I handled that, it became really powerful. So, at my third attempt I managed to produce a decent case which is based on a bottom plate and a cover plate. Both parts hold the PCB in place between each other. I created a model of the Sharp Memory LCD which really allowed me to get a clear idea of how it would look. Finally, I created an animation from the design (it is incredibly how easy and intuitive this was):

You can see that there are four tact buttons, the waterproff USB connector, the bottom spring-contacts for wheel sensor and the Sharp LCD. This is about 4cmx4cm so really small (although could probably made smaller).

There are a few things missing. First, for robustness I should add screws to hold both pieces together. Right now, I will probably rely on friction between both parts for quick testing. The buttons will need to be covered also (maybe I will add a fexible tab). I don't think I will worry about waterproofing yet, that can be dealt later. Finally, some mounting mechanism is needed, maybe I will copy the twist-lock design of most bicycle computers.

I will also need to design a mount for this, which will expose the sensor contacts. Not sure yet which kind of contacts to use. I could make a really simple PCB and use pads, but maybe there's an easier way. Another option for the moment would be to buy a really cheap computer and break out the contacts to a custom housing.

Anyways, now that PCBs will be arriving (tomorrow, supposeddly), I only need to buy a bunch of passives locally which may take a few extra days. So, really soon I will have a finished prototype to test. I plan to make some videos of the build process (using an external camera and digital microscope), so stay tuned for that.

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