Backyard Meteorological Instrumentation

Site One Physical Layout

"Site One" has been cleared on weeds  and edged with old border slabs.

Another edged area with a concrete base has been  created inside that area and it will be where the box of electronics will be installed. The cables from the shed will come from the left of the image and along the upper edge of the outer border. and pass under the edge and come up next to the inner border.

The next step is to level the sensor area and sew it with grass. Bare dirt can heat up significantly and disturb sensors with radiated heat, although that wll happen anyway because of the metal fences. In reality, a grass surface  makes it less likely that dirt will be tramped back into the house, creating a "domestic disturbance".

The air quality sensors will need to be mounted externally from the electronics box as the electronics box only has limited ventilation. To adequately expose the sensors, they will be placed in a ventilated solar radiation shield and mounted on one of the enclosure's poles or the pole behind the enclosure installation.

Mounted in the bordered area and away from the enclosure will be the sensors like the thermometer/relative humidity sensor, the ground temperature and soil moisture sensors.

Main Equipment Shelter

The 540mm x 600mm x 255mm main equipment shelter is to be mounted in the concrete pad area in the above photo, with the door facing the rear fence for easy access. The power, LAN and sensor cables from the shed, as well as the sensor cables exiting the shelter do so via cable entry holes on the bottom of the shelter. The underground conduits are  being installed.

Internally, there is a removeable 350mm x 370mm x 12mm metal mounting plate that will be used to mount the equipment inside the shelter. Using this mounting plate means that no additional equipment mounting holes need to be drilled in the shelter walls, reducing the risk of water ingress.

The shelter has four (4) mounting holes on the rear to bolt the shelter to fence posts set into the ground. The tops of the posts that extend above the enclosure will be used to mount radio antennas for digital receivers.

The box is mounted on two 50mm x 50mm x 1800mm posts. Each post will be set 400mm into the ground with concrete base, The bottom of the box will be set 400mm from the ground, allowing 400mm above the box. The tops of each post are capped to keep out the rain.

Power & Communication Conduit

The enclosure obtains power and Ethernet for local communications via the garden shed. To ensure that these cables do not present a trip hazard, they are buried in a conduit.

There are four cables, plus a draw string, in the conduit. There are two Ethernet cables to provide GigE (1000Base-T) data communications, a +24V 5A power cable and a status cable.

The conduit is only about 75mm under the ground and is not covered by underground detectable tape. This is because there is little likelihood that anyone will dig in this area, and the maximum voltage in the conduit is +24V.

It is expected that additional conduits will  be installed from the enclosure, but as the details are not known yet, the trenching was filled in after the cables were inserted into the conduit.

The +24V power cable was taken off a roll of 15A automotive power cable. The Power cable has a red wire for +24V and a black wire for 0V. Although the cable is rated at 15A, there is a 10A fuse in-circuit between the power supply and the enclosure. The mains 24V power supply is internally limited to 5A. The cable will be terminated on the DIN Rail connector rail for distribution.

The status cable uses a 6-wire security cable and will also be terminated on DIN Rail connectors for later use.

The two (2) Ethernet cables were made by doubling over a very long commercial Ethernet cable and trimming to length in the shed. This required that the cuts ends were terminated to connect to the Ethernet switch in the shed. The patch cable connectors are straight through using the T568B configuration. One Ethernet cable will be used to connect the Raspberry Pi to the home LAN, while the other cable will be a spare, although later it may be used for a video camera.

Licenced under Creative Commons Attribution Share Alike 4.0 International or better by Mark Little (2022 - 2023)