QPLOX has engaged itself on the realization of a demonstrator for a wireless Air Quality (AQ) assessment station connecting a variety of sensors to the central IT services of the User Case partner Sandvik or the cloud, in the context of the ECSEL EU sponsored project codename “CHARM”.
One of the CHARM goals in the underground galleries mining proposed by Sandvik is to build a wireless Air Quality (AQ) data connected station capable of operating in the harsh environment prevailing on underground ore extraction operations: high number of airborne particles or dust, variable air composition, variable and high concentration of water vapor, machinery water jets, violent air pressure changes and shock waves due to nearby rock blasting operations, to name a few.
We do not enter in details discussing role and use of an AQ station in mining operations here. Qplox acts as a technology enabler on the project, presenting solutions to gas sensor manufacturer partners and user case owner specifications and requirements. We just mention here that target underground mining tunnel is endowed with a communications infrastructure comprising 4G-LTE and WiFi coverage along galleries, which can be used to create a connected network of IOT sensors. Low voltage power is supplied by means of wall fixed posts or large battery vehicles for mobile stations. WiFi seems to be a key infrastructure for M2M communications in this environment. The AQ station should also have reduced dimensions, allowing mounting on tunnel walls, or be used as a mobile device for vehicle mounting or, eventually, personally portable, and fed by a 24V DC power distribution network.
Two kind of scenarios were considered by QPLOX: 1) a standing remote AQ station having a fixed 24V AC position inside the tunnel and 2) a mobile station to be ported by an autonomous vehicle providing 24V AC power from vehicle batteries. Clearly, low power consumption is an important requirement in both scenarios, considering the number of fixed and mobile sites where a station and other power consuming equipment could be operating, at great distances from the incoming converter station. Roaming device capability is also a must for mobile WiFi devices mounted on vehicles. IOT security in communications and automatic remote provisioning is also a requirement for industrial connected systems, be it for wireless or connected stations.
Our solution for a multiple sensor station has an accent on component modularity and board-to-board communication standardization. Purpose is to deploy a scalable system, allowing incorporation of new sensor hardware with least effort as possible.
The architecture supporting this solution considers two kinds of dedicated microprocessors: one processor to support the sensor analog front end (AFE), the readout (RO) systems and the serial link protocols to control the sensor and receive the data stream. Another processor provides the wireless connectivity and the WiFi station configuration mode. Tasks related to output of meaningful and calibrated data may be distributed between both processors, depending mostly on the task complexity, computation power and memory available for these tasks.
Each sensor AFE and RO has its own serial communications port (I2C) wired to a switching subsystem that, in turn, links one sensor channel via I2C to the wireless communications processor having a full WiFi stack for communications. Provision for local storage during power-out periods is optional at the wireless communications processor. See figure 1 below.
Sensor AFE and readout subsystems are also eventually provided with an independent WiFi module for eventual individual independent usage outside the station and a USB connector for out-of-the box operation via a laptop.
The demonstrator will in last term have capability for eight independent sensors, but it could be easily be expanded to higher numbers by adding switching modules, with a minor increase of the software complexity and response time.
Two kind of measures are proposed to protect the gas analyzing sensors and electronics from environmental attacks. On one hand, measures for sensor protection are taken by sensor developer teams by means of SENSOR encapsulation, leaving as much as possible just the sensitive surfaces exposed. On the other hand, we propose boxing the whole electronics and sensors inside a waterproof hermetic chassis and force filtered air through the sensors to protect the sensors and electronics from particles and water jets. This concept allows using COTS electronics as much as possible to reduce costs.
Interested? Request additional information on our sensor systems to email@example.com subject CHARM-sensors