Hmm, because the wires are tightly twisted wouldn't any noise be=20
cancelled out?

When I touch the case and wires the count goes back to what it is=20
without me touching the wires.

Gordon


On 16-09-17 11:30 PM, Gordon Williams wrote:
> Sitting down, standing up, etc. doesn't change it. It is very repeatable
> and steady.  But having one hand on the wires and the other touching my
> desktop case does!
>
> Gordon
>
>
> On 16-09-17 10:53 PM, James Cameron wrote:
>> Environmental RF induced into your body will be passed through your fing=
er, changing the voltage unpredictably.
>>
>> You may have a different result if you repeat the test inside a faraday =
cage, or change seating position or hip angle; thus your wavelength.
>>
>> On Sat, Sep 17, 2016 at 10:35:12PM -0400, Gordon Williams wrote:
>>> Hi,
>>>
>>> I have an arduino nano where I am using a red LED for a light sensor.
>>> It seems to be working well and has good sensitivity, but there is some
>>> effect that I don't understand.  I hope someone can provide an explanat=
ion.
>>>
>>> The setup consists of an LED with a 220 Ohm resistor soldered to one of
>>> the legs.  The light/resistor than gets connected to pins 7 and 8 on th=
e
>>> board through a pair of twisted wires.  I reverse bias the LED to charg=
e
>>> it up then change the positive pin to an input and read it in a loop
>>> while counting how long it takes to go from high to low as the charge
>>> bleeds off the LED.  The more light shining on the LED the faster the
>>> pin goes from high to low and the lower the resulting count.  All this
>>> works as expected.
>>>
>>> The thing that I don't understand is when I touch the twisted wires the
>>> count decreases indicating that the charge is bleeding off faster.  I
>>> understand that there is likely a capacitance effect from having my han=
d
>>> close to the wires, but I would have though that this would have
>>> increased the capacitance and therefore this should have taken longer
>>> for charge to bleed off and not shorter.  Does the fact that they are
>>> twisted have anything to do with it?  If I wet my fingers before I touc=
h
>>> the wires it seems to become a lot more sensitive to touch as you almos=
t
>>> don't have to touch the wires before you see the effect.
>>>
>>> Thanks,
>>>
>>> Gordon Williams
>>>
>>>
>>>
>>>
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