This article is about a small sensor node with a decorative case. It is based on the Raspberry Pi Zero W board with a custom sensor shield on top.
I publish all hardware files for a simple version of the sensor, so you should be able to build this kind of sensor nodes and use it to monitor anything you like. You can also extend/modify the design easily with additional sensors. Nevertheless, the case lid design is based around the Plantower PMSA003 particle sensor. It has all required air vents for this use.
The term “node” is used, because the idea of this sensor is to use a large number of these nodes in a network to monitor location and time based sensor data.
I cannot publish any software at this point, until I have a simplified and redacted version which I can publish under an open source license. Yet, accessing the sensors of this node is dead simple and can be easily done.
The Required Hardware
The simplified design is assemble using the following components:
Raspberry Pi Zero W with soldered headers.
Minimalistic Custom Shield (see description below)
Four short M2.5 screws and nuts to fasten the Raspberry Pi in the case.
Optional four M2.5 10mm long spacer to also fasten the shield.
One or two short M2 screw to fasten the Plantower sensor to the shield.
USB Cable and power supply to power the node.
The Raspberry Pi Zero W
I use the Raspberry Pi Zero W because of the very compact size and computing power. Each node can prepare the sensor data, which takes a lot of load from the central processing unit. Also, using a platform like the Raspberry Pi easily allows to run a whole web server on each node – so one can query the sensor data of each node independently. This makes testing a breeze.
I designed a very simple power converter for the snow flake decoration. The snow flake boards require 3.3V, a voltage which is not commonly available in a household. Therefore the power converter takes 5V USB power and convert it into the required 3.3V.
There is no fancy circuit inside of this box, lazily I simple used a Traco Power TSR2-2433 DC/DC power converter. It is a single component containing everything required. No external components like capacitors or resistors needed.
Yesterday I found some time to put the fan controller in a casing. I used a very cheap no-name case with the dimensions 130 × 68 × 44 mm. First I drilled some 2.5mm holes into the lid, and fastened the Arduino board on it using M2.5 spacers. You see the bottom of the case in the photo – I mounted everything top down, because this simplified everything.
I experimented with the spacer size, until I found the right height, so the display is more or less at the same height as the case bottom. Next I put very small bits of double sided tape onto the corners of the display and put the case bottom on top of the lid. After removing the bottom, the exact position of the display was marked at the bottom with these double sided tape bits.
First I drilled four holes at the expected corners to see the position from the other side. Next I used a Dremel tool to cut the rectangle out of the case.
As usual: This was my expectation of the result… 😉
…, and this was the actual result:
No, seriously, I did not expect much. I just hoped the controller will fit into the case and I cut the rectangle at the right place. So, this worked out very well.
Today I worked on the case for the Outmoded Sequencer project. Originally I planed to use acrylic glass and laser cut it, but I did not found a service where I could cut a single piece cheap. So I am using wood, cut it to the right size using a Dremel tool, then sand it and spray painted it black. The color is a really deep black, which is not perfectly visible on the photos because of the black background.
You see a smaller panel with the two knobs and the speaker, which will be mounted on the top area of the larger base. If you look closely you can see the holes where the top panel will be fastened using the distant bolts.
I am using M2.5 threads with 2.8mm holes and distant bolts of 20mm length. Sadly there were no black distant bolts in this size, there were only M3 ones.