[Lab] Arduino CapSense library + Shiftbrites + interference

Tom Burns tom.i.burns at gmail.com
Wed Apr 13 11:55:28 EDT 2011

On this topic (I build synthesizers and for some reason keep using plastic
cases so the it is relevant to my interests)

Usually when wrapping something in tinfoil the next step is to attach the
tinfoil directly to ground.  I'd be interested if you find a noticeable
difference with the tinfoil attached to ground compared to tinfoil not
attached to ground.


On Wed, Apr 13, 2011 at 11:52 AM, Adam Hill <theadbo+modlab at gmail.com>wrote:

> Hi Andrew,
> I suspect that your EMI thesis is the correct one. I see that on the CapSense
> arduino page <http://www.arduino.cc/playground/Main/CapSense>, it notes
> that "At its most sensitive, the sensor will start to sense a hand or body
> inches away from the sensor" so I'm sure the array's are sufficiently noisy
> for the sensor to notice, especially when they're shifting! You could try
> wrapping the cables in tinfoil but other than that I can't think of any good
> solution except to put the setup into some kind of Faraday box<http://en.wikipedia.org/wiki/Faraday_cage>
> .
> BTW, care to share a few pics of the setup?
> -a
> On Wed, Apr 13, 2011 at 11:07 AM, Andrew O'Malley <aomalley at gmail.com>wrote:
>> Hi everyone,
>> I have a pretty specific situation here that I'd love to hear your
>> thoughts on:
>> I have four panels of 5x6 Shiftbrite arrays, attached to plastic
>> supports.  In front of each panel I'm placing an acylic sheet for
>> diffusion, and on this sheet are several wires attached to an Arduino
>> running the CapSense library.
>> I can get useable data from the capsense arrangement running by
>> itself, but when placed (3") in front of the shiftbrite arrary, the
>> capsense values become extremely unstable (huge fluctuations making
>> the data unuseable) when the Shiftbrites are receiving data.  The
>> capsense circuit and the shiftbrite circuit are electrically isolated,
>> as the capsense circuit is running from its own battery while the
>> shiftbrite circuit is plugged in via a power supply; so I don't think
>> it's noise from the power supply.  Is it possible that the array of
>> Shiftbrites are giving off significant EMI while shifting data?
>> If this is the case, anyone have any suggestions for add-on shielding
>> for the shiftbrite array/cables?
>> Thanks for your time and attention!
>> Andrew
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