Beehive Instrumentation Project-5: Case Installation and Temperature-Humidity Measurement Test in Hive


In this installment, I show the installation of the Raspberry Pi 2B into an obsolete NiMH charger case, along with the switching regulator to convert 18V to 5V.

Charger case RPi test fit

Test fit of the RPi 2B into old Ryobi charger case.

For the first test in one of our bee hives, I connected the Adafruit’s HTU21D-F breakout to the Pi’s GPIO header with a solderless prototyping board and proto jumper wires.

RPi Li-ion case install and Hive Test

Prototype board connection of T-H sensor to RPi.

I have mounted the sensor in a cut down plastic potting box, with 1/8″ holes for airflow.  Hopefully the holes will exclude bees, but not make it easy to plug with propilis.

T-H sensor case

Case for HTU21D-F breakout. (Potting box from DigiKey.)

For an initial test, I set the battery-computer assembly on the inner cover in the hive, and draped the T-H sensor through the access hole in the cover, on top of the frames.  (As is typical of Alaska beekeeping, we are still sustaining the bees with sugar syrup. Should have nectar in a week or so.)

I was skeptical about the long-range WiFi through the aluminum-clad top cover out in the yard, but the longer range WiFi USB dongle (Adafruit) is providing a very strong signal.

RPi inner cover test 6-10-15

Still using the Python code posted by Davespice to configure and read the sensor (see installment 3):  https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=76688

I’m operating the RPi through Putty SSH, as before.

Temperatue Humidity 6-10-15-1

The results show temperatures around 23 deg C (73 deg F) and relative humidity at first of about 47% (the RH fluctuated down to ~41 % after about 20 minutes, then rose again–not sure why).  The home weather station shows about 62 deg F and 52% RH.  The difference in humidity is probably due to the temperature difference, but I sort of expected it to be more humid in the hive, with all the sugar syrup curing in there (lots of pollen, but still waiting for the major nectar flow to start).
I was planning to build a small enclosure to hold the computer and battery at the back of the hive box. If the system works okay inside a spacer box on top of the inner cover, though, I might just stay with that.

Further intended developments include:

  • IR camera and illuminator (Pi NOIR camera)
  • A multiplexer for T-H sensors in additional hives.  This should allow a row of hives to share one RPi and battery for economy.
  • Battery monitoring.  Also have a few parts lying around for a solar charger with 4xAA batteries.
  • Hive weight measurement, taring, calibration, and logging.
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