By now I've found many applications for the MGC3130 3D gestured recognition IC - if you're interested please see my other blog posts about what I've done with it- so of course I want to start creating my own devices using the chip.

 

One important consideration systems that rely on generating and sensing tiny capacitance disturbances to an e-field system is of course the electrodes. Fortunately the MGC3130 seems to be very tolerant and the datasheet lists a wide range of suitable materials:

 

  • Printed circuit board
  • Conductive paint
  • Conductive foil
  • Laser Direct Structuring (LDS)
  • Touchpanel ITO structures

 

At the very least you need one transmission layer and 4 or 5 receiver electrodes. The layers should be separated by about 1mm-1.5mm but in my experience the MGC3130 seems to tolerate more. Optionally you can add a ground layer, behind the transmission layer. This seems to help filter out some noise, but it's not required.

 

The  modular nature of Hillstar development Kit is really good for this since you can connect any electrodes you want, you don't need to use the 95x60 electrode they provide. I even tried using kitchen foil, with some success (but too much noise, maybe due to the poor connection - I was using crocodile clips) and/or poor separation.

 

One of the materials that has caught my interest recently is inkjet printed, copper plated, circuits printed on flexible, 300 μm thick, Melinex from DuPont... aka "plastic" for everyone else This is a service provided by Cambridge (UK) based InkJetFlex on their rapid prototyping offer. Essentially you can print any number of circuits onto a 280mm wide roll of any length you need. Then you pay by the meter, £50, which is a lot cheaper than PCB . You can also solder any surface mount component to it using low temperature (bismuth-based) solder - don't go over 150C or the Melinex wrinkles up.

 

So my plan is produce electrodes for the Hillstar development kit using this technology. I sent a few designs to be printed and they're almost ready.

They sent me a photo of the non-plated, just inkjet printed, material today. This will then be plated with copper next week.

 

Unplated print1.jpg

 

I'll keep you updated on how well the copper inkjet printed sensors work with the kit.