NEXO IoT Weather Station
A low-cost, agrometeorological weather station for smallholder agriculture.
Currently, only 10% of the smallholder farmers in sub-Saharan Africa receive any form of value-adding service. These services, ranging from simple farm management advice, to complex products such as access to loans or insurance, all help to increase the profitability of farming and gradually lift farmers out of poverty. Our mission at Climate Edge is to vastly increase the number of farmers who have access to such services, and to improve the livelihoods of smallholder farmers across the globe.
The NEXO weather station was our first effort to design a low cost device to collect climatic data for smallholder farmers. High resolution climatic data is vital to improve farm management practice and therefore quality, quantity and profitability of farmers.
Many agricultural information services require this data to deliver value, for example, we are working with scientific partners on delivering irrigation scheduling for bananas to smallholder farmers. The mathematical model uses data like soil moisture, rainfall, temperatures, etc. to calculate the water deficit in the soil and suggest an optimised irrigation schedule.
James Dyson Award - National Runner up, UK
The NEXO IoT weather station was selected as National Runner Up for the UK by the prestigious James Dyson Foundation
Learn more about the prototyping process
Developing the NEXO
The design process of the NEXO IoT weather station followed an agile and iterative process of build, test, review. As Chief Design Officer my responsibilities included managing the hardware development process, coordinating external engineers, suppliers and clients, as well as planning and executing all hardware prototyping and guiding the external PCB design.
We designed, tested and deployed 4 different versions of the NEXO weather station, each of them provided valuable lessons around usability, functionality and viability of a device like it.
Here are some details about each version, starting with the first proof of concept NEXO 1.
NEXO 1 - Proof of Concept
The NEXO 1 was a proof of concept which I constructed from a combination of adapted off-the-shelf components and custom designed 3D printed parts. Its main purpose was to test the value of data collection in the tropics for a limited time period of half a year.
Our client was Fairtrade International and we designed, built and tested these devices in only 6 months before installing them on smallholder coffee plots in Nicaragua in 2016.
We purposefully avoided power hungry mobile network connectivity for data upload or solar powered battery charging to increase testing speed and robustness. Rather than an autonomous and permanent data collection solution, this first NEXO stored data on an SD card and was retrieved from the field at the end of the project.
NEXO 2 - Automatic and remote
For the second iteration of the NEXO we introduced several features that would allow the weather station to work fully remotely and automatically.
We introduced powerful Lithium-Ion batteries which were charged by solar panels and a GPRS module to hold an international SIM card.
From arduino based electronics, we move to a custom designed circuit board
To have more control over the assembly process and end result, I replaced several off-the-shelf components with custom design parts
To prepare for scalability, I designed these custom parts to be liquid moulded or vacuum formed
To ease the set-up process and repairability, we replaced soldered connections with pluggable connectors
NEXO 3 - Design for Manufacturing & Assembly
The upgrade to the NEXO 3 represented a major push in design for manufacturing and assembly (DFMA). There were hardly any off-the-shelf hardware components left in the design and we invested into a professional 3D printer which would allow us to manufacture most components in-house.
We intended to build over 100 stations using our 3D printer, which set a clear priority to optimise the parts for 3D-printability. However to eventually manufacture at scale we were starting conversations with injection moulding factories and I paid close attention to construct each part to be ready for injection moulding with only minimal geometric changes.
The aluminium and stainless steel components were cut by our UK suppliers on state of the art CNC metal fabrication machines for a cost that was already close to scalable manufacturing.
NEXO 4 - Optimise for scale
The fourth version of the NEXO was another significant improvement in several ways.
Optimisation on the firmware offered big power savings and improved error identification
We introduced and innovative LED interface which could display the stage of the set-up process and error codes for improved trouble shooting (such as: low battery, no mobile connection, etc.)
During factory visits in Shenzhen I was successful in sourcing custom batteries and solar panels
Changes in like the smaller solar panel simplified the structural design and the bill of material substantially, reducing cost and installation time
Entirely 3D printed housing of the NEXO 4 including:
bayonet locked lid with snap lock
heat welded threaded inserts
bayonet lock air sensor
thin-walled LED windows
printed with DFM/DFA in mind