Finalising the hardware
This week was spent designing and assembling the finalised hardware. I made the realisation that placing the fans back to back as in my original quick mock-up would not be the most intelligent way to mount them as the fans would both be obstructing each other. Instead, I have designed the final hardware with this in mind and stacked the fans vertically instead, allowing clear intake and exhaust for both EDFs.
Using my previous static test stand model as a base, I designed the final carriage parts to hold the fans in place. I also added cable management loops to make sure the wires for the upper fan are safely out of the way during operation.
The upper part and both fans are held securely in place using an m3 x 100mm bolt, screwed into some brass heat-set inserts in the base of the stand.
As with the previous mini test track, I plan to use laser-cut MDF to interface with the rail slider, but the final version of the carriage also needs a place to mount the batteries, sensors and microcontroller. I have designed a system that will use two MDF plates, separated by standoffs with the other components mounted between them.
After modelling the lower plate at a size I thought was sensible, I drew a scale diagram of it on paper and tried arranging the components in different layouts to make sure everything would fit correctly.
My initial plan was to 3d print mounts for each individual component and fix them to the MDF plate with screws, but this would mean I would need to decide on a layout in advance without being able to easily switch the positions of components around. To combat this, I instead added a grid of holes to the model of the lower plate so I can zip-tie each of the components in place, along with any wires to keep them secure.
Regarding sensors, I have finalised my decision on the sensors I will be using too. Of course the feedback signal from each fan will be used and alongside it, I have decided on an Adafruit BNO08x 9-DoF IMU which I will use to measure linear acceleration and a DFRobot SEN0366 IR laser distance sensor (ordered, and should arrive early next week). This distance sensor is impressively accurate, at just a 2mm standard deviation between 1 and 5 meters.