This is the first prototype of the housing for the electronics. It has been developed in the 3D modeling program, SolidWorks, and sent to a rapid prototyping machine to be formed.

I originally considered using the prototype as a mold to produce plastic casings. I have no experience in mold making so I consulted people with experience in this matter. I was informed that the tolerances of a 1/16 inch that I am dealing with could be problematic in the mold making process.

Considering this information, I tested the robustness of the ceramic prototype and was pleasantly surprised. I subjected the prototype to abuse (i.e. by dropping the prototype on floor, by squeezing it in a clamp) and it is apparent that it is more tolerant to strains than the pint glass that it will be affixed to.

The rapid prototyping process is relatively inexpensive (>$5 per piece), and in small quantities (>20 pieces), it seems economical to just use the ceramic prototypes instead of producing plastic versions of the casing.

I wanted to squeeze the electronics into a smaller area, but with the tools that I have access to, the casing that I have produced seems like the smallest I can go at this point. My desire was to fit everything in a 1/2 inch puck glued to the bottom of the glass, but the size of the 850 mA Li-ion battery alone makes this desire improbable. I may be able to go smaller in future iterations of this project, but for now, the size of the casing which I am using is acceptable.



Affixed to the pint glass, the image above is what the complete module will look like. Unfortunately, I have not completed the electronics that will be put inside.

I have attached a clear conductive plastic film that skirts the glass to the capacitance sensor in the glass. I have also experimented with other methods such as conductive paint. Conductive paint is opaque and it doesn’t adhere to the glass surface well. I tried creating a meshed mask and then painting on the conductive paint in attempt to give the touch surface of the glass a somewhat transparent appearance, but even covering this coat with a clear liqueur, the paint still has problems sticking to the glass.

The plastic film has achieved the best results even though it has its own problems. For one, it gets dirty really easily. Fingerprints seem to affix themselves to the plastic film quite easily. Also, liquids easily get caught in between the glass and the plastic film. I ameliorated this problem by applying a clear paint around the edges of the plastic. At this point, the conductive plastic is the best solution, but I really want to find a better solution in the future.

This entry was posted on Saturday, November 8th, 2008 at 9:18 pm and is filed under capacitance, package design. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.