ArcoFlex Sensei – Creating Virtual Sensors
ArcoFlex Sensei introduces a brand new concept to the IOT
market: virtual sensors. Not possible on LoRA or single device gateway
solutions, Sensei can combine one or more real sensors into virtual sensors to
represent real data or conditions that are dependent on multiple real world inputs.
What a virtual sensor solves is important. Taking the
example of a bio-security airlock, there are two doors with door switches and the
airlock is in breach if both doors are opened simultaneously. Without virtual
sensors you are constrained to writing code in the visualisation layer or
stream analytics layer which constantly monitors the outputs of two sensors, the
two door switches. Not only do you have to customise the code each time you
need this implementation, the processing workload is now on the server side and
scaling is a problem. If 1000 nurseries need an airlock, the server has to
continually monitor this process for a 1000 sites. It is a massive performance
hit and an unwanted complexity.
Enter ArcoFlex Sensei and a virtual sensor. The Raspberry PI
code will create a sensor from the combined input of both door switches and
report breach data like any other sensor. This is a simple Logical AND where
both doors open creates a breach and even the length of time in breach can be
measured in the visualisation. All processing is done on the remote PI so now
scaling is not a problem. The dashboard merely displays data as if it were another
sensor.
The
key to sensor and device performance is in making the 1000’s of PI’s do the
processing rather than the visualisation layer or the server. The resulting data
stream becomes raw data just like any other data stream. This also allows for universal coding
in the visualisation layer because the output is treated just like any other
sensor.
So far, we have come across several very useful
implementations:
·
Hothouse
Airlock – At the Toolangi Seed Potato farm, bio-isolation is required
in order to obtain certification to sell into Queensland. Whilst the doors can
be rigged with alarms locally, Sensei records breaches (or lack of) and
provides documentation for compliance purposes.
·
Filter
Differential – in our standard irrigation monitoring solution there is
a pressure sensor either side of the micro-filter. A virtual sensor is created
to monitor the difference in pressure across the filter. Once it gets too
great, a new filter is ordered and a replacement scheduled. Again, proactive
alerts are generated to warn of pressure deterioration.
·
Irrigation
line Leaks – when the line is pumping, there is a certain back pressure
that is normal. If the outward leg pressure drops too much when the pump is
running, there is a leak that must be attended to.
·
Pump
Run Confirm – the float switch for refill can be actuated but if the UV
sterilizer breaks, the pump is disconnected. This means that the float switch
alone isn’t enough of an indicator that the pump is actually running. This
virtual sensor might check three inputs to determine if it is actually running.
·
Fungal
Growth Profile – there is a relationship between humidity and
temperature that creates conditions ideal for fungal growth in a hothouse. The
formula for this relationship can be coded into the PI so that raw data can be
fed to the customer as a percentage of ideal.
·
Heartbeat
– based around a simple timer, a single byte can be sent through to the
dashboard confirming that comms and data channels are all in order. This is
critical where you have data which of its nature, changes only very slowly or
not at all for long periods. The heartbeat allows you to very economically
detect the overall health of your sensor array.
·
Trending
Patterns – perhaps you are monitoring air pressure or temperature and
you have a need for a dashboard gauge which simply shows rising/steady/falling
or drier/wetter and so on. Quite often, this fact is a metric of itself or can
be used to combine into alerts and notifications. Defining these at the PI
level solves all those scaling issues mentioned and ensures the output is
recorded as data points of themselves.
With ArcoFlex Sensei, you can build virtual sensors to represent quite complex relationships between other sensors. These virtual sensors generate real time data in their own right but keep all the processing down at the sensor gateway. This makes for fully scalable business logic solutions to generate compound data without processing overheads.
But there is one other use for virtual sensors: output! Being
able to control digital or analogue output is a vital part of remote monitoring
and control. This isn’t just internal feedback, important as that can be, this
is configurable control. Implemented with simple relays, a digital output could
be instructed to turn on or off a motor, a fan, a compressor, a pump or in fact
anything that can take a switched power supply. With a little bit of extra
wiring we can also make an analogue output (something like 0V to 5V) to control
a potentiometer. An example of this might be a thermostat or a stepping motor.
The virtual sensor gives us a structured way to provide
configurable metrics to a digital or analogue input. Expect this to be the growth
zone for IoT going forward. Well, once they’ve solved all the other issue
first.
Geoff Schaller@ArcoflexIOT
google
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