Wireless sensor devices for post-harvest crop quality and pest management
Embodiments of systems and approaches for managing post-harvest crop quality and pests are described. Such a system may include a plurality of edge devices each comprising sensor components and collectively forming a mesh network, for measuring the local physical environment within stored crops and, for example, transmitting the measurements to a service from within the crop storage area. In certain embodiments, such a system may be used to manage post-harvest crops and storage areas—for example, approaches are described for determining fumigation treatment duration, determining phosphine dosage, determining heat treatment duration, and determining safe storage time for crops.
1. An edge device, comprising:
a plastic housing encasing an environment-exposed compartment and a sealed compartment, the environment exposed compartment defined by a cap and an upper housing and the sealed compartment defined by the upper housing and a lower housing, the cap having a first threaded portion mated with a second threaded portion of the upper housing and a plurality of vents configured to allow air passage from an environment external to the edge device into the environment-exposed compartment, the upper housing having a third threaded portion mated with a fourth threaded portion of the lower housing and an upper surface containing a sensor opening;
an electrochemical gas sensor comprising a sensor cell and a sensor circuit board, the electrochemical gas sensor is partially disposed within the sealed compartment and in a fixed position abutting the upper surface of the upper housing such that a portion of the sensor cell protrudes into the sensor opening and is exposed to an atmosphere within the environment-exposed compartment;
one or more upper rubber o-rings circumferentially disposed around the portion of the electrochemical gas sensor that protrudes into the environment-exposed compartment creating a seal that abuts the sensor opening of the upper housing;
a main circuit board disposed within the sealed compartment and communicatively coupled to the electrochemical gas sensor, the main circuit board having a plurality of mounted components respectively coupled to a battery, a reed switch configured as an on/off switch for the edge device, an antenna, and radio frequency (RF) circuitry;
a magnet disposed on a first plastic ring, and a second plastic ring, wherein the first plastic ring is configured to rotate around the fourth threaded portion of the lower housing, disposed between the upper housing and the second plastic ring, rotationally translating the magnet with respect to the reed switch, and the second plastic ring is configured to mate with the fourth threaded portion of the lower housing; and
one or more lower rubber o-rings disposed at an interface between the upper housing and the lower housing.
2. The edge device of claim 1 , wherein the housing is formed from an acetal plastic, such as an acetal copolymer.
3. The edge device of claim 1 , wherein the vents are micro holes.
4. The edge device of claim 1 , wherein the battery is a lithium thionyl chloride battery.
5. The edge device of claim 1 , wherein the monopole antenna is a short inverted-L monopole antenna with an orthogonal meander line top plate having a total line length of a nominal quarter wavelength.
6. The edge device of claim 1 , wherein the first plastic ring is rotatable between two detents representing “on” and “off” positions.
7. The edge device of claim 1 , wherein the number of upper rubber o-rings is two.