Monthly Archives: July 2015
In this post, we had talked about a continuous LPG monitoring system. We built an updated version of the system where we changed the base platform, and used a more rugged and sleek set of enclosures for the load cell’s PCB, and the WiSense node, respectively. A set of CAD renderings of the system is shown here:
These are photographs of the system: that we built:
We used ply-wood to build the platforms, and used enclosures made from ABS plastic. The system been running continuously for over a week now.
We participated in ITC Infotech’s iTech 2015 IoT Hackathon, where we had to build an IoT-enabled product using sensors provided to the participants. One of our submissions was a networked gas-leakage sensor for detecting inflammable gases such as LPG, ethanol fumes, propane etc. We were provided the MQ-5 Gas-leakage sensor.
The working principle behind the MQ-5 gas sensor is as follows: The sensor has a sensitive filament made of SnO2. In the presence of clean air, this filament tends to have lower electrical conductivity. When a combustible gas such as LPG is introduced, the filament’s conductivity rises, and the amount of change in it’s conductance/resistance can be used to indicate the equivalent gas concentration. This effect tends to be particularly pronounced at higher temperatures, and resisitive heating element is present as well. SnO2 is particularly sensitive to Methane, Butane and Propane, but is also sensitive to other combustible gases as well.
The Technical specifications for the MQ-5 sensor are tabulated here:
Table 1 – Technical Specifications of the MQ-5 Gas leakage sensor.
The working of the MQ-5 sensor can be explained using Pic 1. The heating coil H is in contact with the SnO2 filament. In the presence of clean air, the resistance across the heating coil does not vary, but when a combustible gas is present, the resistance of the SnO2 filament drops, which results in a corresponding rise in Output Voltage (Vout), and this output voltage can be measured to indicate the concentration of any combustible gas that is present.
The MQ-5 has an analog (voltage) output. We connected the MQ-5 sensor to a WSN1101L. Data from the MQ-5 sensor could now be transmitted to a WSN1101C gateway and used to monitor a given space for gas leaks etc.
These are some pictures from the project:
We tested the circuit using a partly-opened Cigarette lighter to introduce combustible gas near the gas sensor. See the rise and fall of O/P voltage on Pic 4. (Note: The MQ-5 sensor requires a 48-hour initial heating period as part of it’s calibration process).
This was part of a complete home-automation system that we built.The other modules we built included a wireless system to remotely monitor Load-cell output, a wireless system to remotely monitor temperature and humidity, and a wireless system to remotely monitor soil humidity.