But a bunch of small devices can be managed by a huge device running Linux — maybe even something as expensive as a Raspberry Pi.
(Apart from some time trying to sell in the Ag sector I spent a lot of time on embedded devices)
I hear you that $20 is high - but the status quo in this business now is monitoring devices that sell for AUD $600+, and with LTE-M or LoRa comms modules that cost over AUD $60 alone.
I'm forever thinking about ways you could drive the cost down further. I'd love it if there were a way to get the on-plant modules under $1. Feel free to get in touch if you want to discuss further.
It's an interesting problem and I am sure reference designs already exist. Maybe talk to someone at Nordic.
As I said in the previous comment, right now, high-value crop growers like wine grape growers pay $700-$1000 or more per site (including reader/comms module and sensors), and generally only install one monitoring point per block (I have a system running at one of Australia's top boutique/biodynamic wine makers and at current prices he can only cost-justify having one 10 monitoring sites over his 70 acres of vines).
So, whatever we can do to drive down the cost to $20 or less should deliver big wins.
> Maybe talk to someone at Nordic
Yep, we're working with hardware engineers who are well connected to people at Nordic.
But the economics of farming in the Eyre Peninsula is quite different and they really have a water problem. From a food PoV these are the people we really need to help.
(I have family in both, not to mention in laws in Germany who also have a water problem...getting rid of it!)
Right now it costs about $750-$3000 to set up each monitoring site, so growers can only afford to install a low number of devices per acre [1], thus a high number of plants per device. In that case you’re not optimizing to anywhere the specific requirements of each plant, you’re assuming (often falsely) that all the plants in that area have the same needs as the one you’re monitoring.
The lower the cost per device, the higher your resolution and precision of monitoring can be, and the more you can accurately provide for the specific needs of each plant.
[1] Very often that number is zero.
Wouldn't a device that travels like a snail along a cable or something, while less glamorous than a self propelled (and navigating) device, deliver a reading for a whole line of plants every day without all of the eroding parts per plant?
Having machines moving around taking readings “each day” is insufficient, as during hot conditions the soil/plant moisture changes too rapidly. You need to take readings at least once every hour or even every 30 or 15 minutes in order to be able to start irrigating immediately when the moisture level starts dropping rapidly.
I can imagine that a lot of small devices becomes economically viable.. I find that unfortunate since I think it will be a lot of permanent ewaste lost in fields relative to very temporary water optimization benefits.