Tuesday, 16 August 2016


ArcoFlex Sensei – Solving the IOT Sensor Problem
 
The IOT space – the bit that talks about remote monitoring and control (and most people ignore the control bit) - is full of companies scrambling to provide sensors and devices, vainly hoping someone will know what to do with them. The problem for the solution developer is that none of them are compatible and all of them are different. So how is the average business to navigate this sea of differences? This is where ArcoFlex Sensei comes to the rescue.


Add to that the fact that everyone will tell you WHAT you should be doing, very few, if anyone, actually tells you how. Whilst it is easy enough to code visualisations and dashboards once you have data, how on earth do you get the data out of a sensor and into an event hub in order to extract it down to a visualisation. Let’s look at the problem:

·         you have sensors and now need to wire it to “something” to extract the data
·         Your sensor gateway needs to be able to address the sensor and extract the actual data
·         There is scaling and limits and DAC conversion to be concerned about
·         Digital inputs need some way to get their value into the gateway
·         Code is needed somewhere to find these values, connect with the Hub and send data
Each of these sensors needs to connect to the central gateway computer via an IO card. Unless you’re an electrical engineer or hobbyist with some experience, this is going to be a massive problem so let’s go over the sensor types you will encounter:

One-Wire.          One-Wire devices have an address and you need to determine (or read from the packet someone binned 6 weeks ago). Once you have the address your gateway code will simply read the value in the form of a string. No conversion necessary but you will get 86 decimals places if you aren’t careful. One-Wire is good because the sensors are very cheap and quite accurate. Code is need to loop around all possible addresses each time you want a value.
Analogue.           To confuse matters, there are 4ch and 8ch analogue devices and they scale differently. 4ch sensors are vastly more accurate but you can only have 4 per IO card. They can be either current oriented (4ma) or voltage oriented (5V). they may or may not have a zero setting as an offset. This will further reduce resolution. 8ch analogue sensors can only provide 0-255 as a maximum resolution and if there is an offset, this is often 25% smaller. You need to know all of these characteristics so that you can correctly scale the resulting value.
Digital.                 To operate a digital sensor, you are required to supply a voltage (or 0V) to a set of pins that can be read as on or off. This means providing power to the circuit being switched or sensed.  The same goes if you are supplying a signal back. You will now be operating a relay to switch something on or off that will carry current to the device being controlled.
So the IO cards used to connect sensors need to have compatible input channels and if there are multiple cards, dip switches set to addresses to the cards. The code in your gateway device needs to accommodate all this and try as we might, the smaller Arduino Yun boards just couldn’t carry the programming. This was especially true once we came to the conclusion we needed to manage and compress the collected data. Our conclusion was to move on to a Raspberry PI3 B processor board and Windows 10 IOT Core as an operating system. Linux would have worked too but we’re a Microsoft shop and the attraction of using one language for the entire code base was just too attractive.
So ArcoFlex Sensei was built to solve all these sensor related problems. The basic model includes the following:
·         Raspberry PI3B with 1GB RAM and 8GB SSD card
·         W10 IOT Core and an application to manage the IO cards, all comms and management
·         One one-wire IO card (256+ sensors possible)
·         One 4 channel analogue IO card
·         One Digital IO card with up to 8 inputs
·         A power supply
·         A 4G gateway router and/or RJ45 LAN socket
·         Instructions (Yes!) on how to wire in your sensors
With just a few bits of wire, some pliers and a soldering iron, anyone can wire in any sensor they choose. $5 temperature sensors are a good start but we have taken all the complexity out of knowing how to get data out of a sensor and onto the web. If you obtain one of our starter kits we can also provide the back-end code to visual your sensor data through to a dashboard and even generate alerts.
With ArcoFlex Sensei, you can build a proof of concept device in just a few minutes.

Geoff Schaller
@ArcoflexIOT

2 comments:

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