I want to build a SmartSkin-like architecture. I am familiar with arduino and I found a chip, that seems to take away a lot of the electronics complexity: Freescale MC34940.
It features 7 capacitive sensors, that can be read one-by-one by simply sending 3bits 000->111 => 0=return no sensor value, 2=return second sensor, 7=return seventh sensor value. Although it sound so easy and forwarded, I am a little bit sceptic: Will I need to go through Op-Amp hell? Or will be the signal good enough to do post-processing on the computer?

Does anyone here have some experiences with that chip?

Here you see how it should look like:
moto’s capacitive multitouch

No experience with that but I’m very interested in it.
Please share your progress.

Tinkerman - 01 July 2008 10:52 AM

No experience with that but I’m very interested in it.
Please share your progress.

I will. and I hope, someone will join my attempts some day. on the weekend I will set up a blog (finally: a topic to blog about :D).

I am expecting the chips to arrive tomorrow.

Stay tuned

Does anybody know, what kind of tape is used for the antennas?

vikingosegundo - 01 July 2008 08:17 AM

I want to build a SmartSkin-like architecture. I am familiar with arduino and I found a chip, that seems to take away a lot of the electronics complexity: Freescale MC34940.
It features 7 capacitive sensors, that can be read one-by-one by simply sending 3bits 000->111 => 0=return no sensor value, 2=return second sensor, 7=return seventh sensor value. Although it sound so easy and forwarded, I am a little bit sceptic: Will I need to go through Op-Amp hell? Or will be the signal good enough to do post-processing on the computer?

Does anyone here have some experiences with that chip?

Here you see how it should look like:
moto’s capacitive multitouch

vikingosegundo,

I experimented with SmartSkin-like input methods a while ago. Single MC34940 chip will not work in this particular application because its electodes are internally couppled to the built-it sine wave oscilator. Because of this you’ll not be able to detect multiple points in 2 dimensions. You might be able to do something by using one MC34940 for 7 X coordinates and another MC34940 for 7 Y coordinates. Then you’d have to power each chip independently and read their analog output.

Note that this is not how SmartSkin circuit works. One problem that you’ll face is the limited length of the electrodes.
Therefore it is better to build your own circuit and go from there.

~Alex

AlexP - 03 July 2008 01:07 AM

I experimented with SmartSkin-like input methods a while ago. Single MC34940 chip will not work in this particular application because its electodes are internally couppled to the built-it sine wave oscilator. Because of this you’ll not be able to detect multiple points in 2 dimensions. You might be able to do something by using one MC34940 for 7 X coordinates and another MC34940 for 7 Y coordinates. Then you’d have to power each chip independently and read their analog output.

With this early prototype i dont want to replicate the smartskin technology. I want to try-out some things

AlexP - 03 July 2008 01:07 AM

Therefore it is better to build your own circuit and go from there.

How far did you come? Do you have some circuits for me?