[VicPiMakers Projects] Nap logger

[George Bowden]

Hi all
Implementation of my logging of naps continues:

   1. 10cm x 30 cm  light weight aluminum sheeting under mattress cover
   2. feeding into 4ft twisted pair
   3. feeding schottky diode
   4. (I'd like to amplify the signal at this point by a factor 5) HELP!
   5. feeding mcp3008 ADC
   6. feeding raspberry pi b+ SPI input

One wire of the twisted pair is grounded  to earth and the other end is
unattached at the foil. I thought this might reduce antenna pickup between
foil and ADC.

I'm currently measuring the 1/2 volt amplitude of the 60 cycle hum picked
up by the foil which is reduced by half when my body is on top of the
foil.  The mcp3008+RPI can sample about 100 times per 60hz cycle... good
enough.  Here is a plot of those samples.  1024 would be max amplitude

[image: image.png]

Below is a chart from midnight to noon. I got up a couple of times in the
night, then I got up around 8am, then again at about 9am,
The blue "short" line is a thermistor reading the room temperature, and red
"long" is a thermistor reading temperature beside the foil, for a check of
antenna sanity.
The yellow line, "cap" , is an integration of  a positive half cycles,
divided by 10.  I take measurements every 10 minutes.
[image: image.png]
Next I need to add the amplifier,

--[image: image.png]

and then some logic to turn on the alarm if my afternoon nap  goes over an
hour.😯

George Bowden  250-893-7423
Victoria BC
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