Air Quality
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The SDS011 sensor, that uses a fan to draw in 'new' air that is 'measured' and then expels it back out again, is held in a custom 3D printed framework contained in a length of standard (UK domestic plumbing) PVC tubing. Standard fixing bands for the PVC tubing can be used to mount the overall assembly onto a wall as shown in the two images top right for two completed builds that are mounted either indoors or outdoors.
This framework, shown schematically below, has a bottom plate and top cap that are held together by two 150mm long 8mm diameter wooden dowel rods. The various framework elements that hold all the electronic components, and the cap + plate, are custom 3D prints (all the 3D print designs can be downloaded from the Prusa web site here). This overall asembly is then 'slotted into the PVC tubing.
The electronic components and interconnect cables comprise:
- a DHT11 temperature and humidity sensor that is fixed into the bottom 3D printed plate and held in place with a 6mm M2 self tap screw;
- a DS18B20 temperature sensor, of the type that is sheathed in a metal tube, that is a tight fit through a hole in the bottom plate;
- a BMP180 pressure and temperature sensor that is held in place with a 8mm M2 self tap screw that also 'pins' one of the wooden dowel rods to the top cap;
- a Raspberry Pi Zero, used to control and manage the system, that is screwed onto the 3D printed mounting frame with 6mm M2 self tap screws - small 3D printed washers are used so that the Pi 'stands off' the mounting frame a few millimeters as the male header GPIO pins protrude a short distance out of the back of the Pi;
- a x3 USB-port + ethernet port adaptor, used to expand the Pi's IO options by connecting to the Pi's micro USB connector, and is a slide fit into 3D printed 'strap' and 'saddle' components; and
- a passive splitter cable adaptor that takes its input from an ethernet cable and 'splits' this feed to a power cable via a bullet connector to the Pi's power input connector, and the ethernet signal to the ethernet port on the USB port + ethernet adaptor.
The first four images below show the 1st completed build with the un-sleeved unit sitting upside-down from various angles. A final sleeved assembly, still shown upside-down, is shown in the 5th image below and the first image at the top, right of the screen shows the completed unit positioned indoors in the corner of a hallway (the right way up!) in its final production deployment position.
This next series of images show the 2nd completed build in a more detailed set of steps from the initial assembly of the 3D printed framework components, through to the fixing of the various components, and on to the final un-sleeved upside down assembly viewed from various angles:
For both builds the unit's connectivity and power are provided through a single ethernet cable (up to about 6 to7m in length for the unit deployed outdoors) where passive splitting of power and data are carried out using an adaptor both within the overall assembly and at the far end of the ethernet cable which connects to the local network and a 5VDC power supply.
All the details of this Air Quality Monitoring project:
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