Inductive Sensing Design Challenge: USB Microphone based on the LDC1000 Inductance to Digital Converter (week 8 & 9)

I am still working on this project, but again it has been very difficult to find the time to finish things up. It has been a very hectic period at work and I've also just signed a contract for a new job next year. I've also had a ton of practical problems with the actual fabrication of all the parts.

First of all the 3D printer at my work (an original Ultimaker) is malfunctioning. The extruder seems to be broken, because the plastic gets smeared all over the nozzle during printing. I spent a day trying to fix it, but after taking apart the printhead, cleaning the nozzle and putting it all back together the problem was not solved. In the end I decided to use an online 3D printing service (Sculpteo), because I just do not have the time to get the Ultimaker working. In my honest opinion the construction of the Ultimaker is very poor, so if you are in the market for a 3D printer I suggest you get a different model.

Anyway, I just got the 3D printed rings I mentioned in the last blog post. The quality is pretty good, but I think I might have been better of choosing the flush finish (you can choose between rough or flush). As mentioned before, the two rings fit together to clamp a piece of Aluminum foil. I tried it out with some Aluminum foil, but the foil I have is very thin (13µm) so it just ends up getting torn. Here are some shots of the rings:

I did order some thicker foil online too, but I have not received it yet. It was also quite difficult to find an affordable source of Aluminum foil which was thick enough. There are plenty of adhesive tapes which are 100µm, but I don't think they would serve. In the end I got some 130µm tooling foil, which should be good enough for a basic test.

The final problem I'm currently having is finding an affordable PCB prototyping service which offers 4mil resolution for trace width and distance (this is the resolution required for a webbench produced coil). The process I typically use has a minimum trace width of 6mil so I can't use that.

The following image shows what I want the coil to look like. The PCB will be attached to the two rings with 2mm bolts (probably plastic).

Obviously I do not expect a high quality response out of this prototype, but if I could get it to pick up some sound it would prove the theoretical concept is sound (no pun intended).