[Lab] Arduino CapSense library + Shiftbrites + interference

[Andrew O'Malley]

Interesting, I'll try adding the small capacitors.

I find the capactive sensing works fine off the battery powered
circuit, despite not having the second electrode (foil), so long as
the shiftbrite circuit is off.

Thanks,
Andrew


On Wed, Apr 13, 2011 at 12:44 PM, Jean-Marc LeBlanc
<jeanmarc.leblanc at gmail.com> wrote:
> when running on a battery (non grounded circuit), you need to have
> your hand pass between 2 tin foils where as if its get power from the
> USB (grounded circuit), only one foil is required.  That is my
> understanding of it.  I am not sure how you have it set up I am going
> off what I ready here
>
> http://blog.hodgepig.org/2010/09/16/launchpad-capacitive-sensing/
>
> quote:
> "If your Launchpad isn’t grounded (ie. running from battery power),
> add a second foil to ground and move your hand between them.
>
> I’ve found that when using a small capacitor alongside the foil I see
> less background noise."
>
>
>
>
> Jean-Marc Le Blanc
> ---
>
> "Do you pine for the nice days of Minix-1.1, when men were men and
> wrote their own device drivers?" Linus Torvalds
>
>
>
>
> On Wed, Apr 13, 2011 at 12:13 PM, Andrew O'Malley <aomalley at gmail.com> wrote:
>> Hi all,
>>
>> Thanks for your replies thus far.
>>
>> @Charles, the acrylic sheet is integral to the design as it is the
>> diffusing material.
>>
>> @Tom + Adam I'm going to try the tinfoil shielding tonight.
>>
>> Here's a preview of what we're working on, including pics of the inner
>> electronics and renderings of the outer enclosure (the acrylic will be
>> the windows):
>> http://www.facebook.com/album.php?aid=289063&id=101546226937
>>
>> Cheers,
>> Andrew
>>
>>
>> On Wed, Apr 13, 2011 at 12:07 PM, Charles Richer
>> <charles.richer at gmail.com> wrote:
>>> Silly question does it make a difference whether you have the acrylic sheet
>>> or not.
>>>
>>> --cr
>>>
>>>
>>> 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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>>>
>>>
>>
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