Boards passed review, were fabricated at @oshpark, and are here being tested with our latest body. There were some issues with the pads being too close, but we were able to salvage one. @Steven.Carr is now in the process of building a calibrated flow source. Probably some form of piston/pvc pipe and a stepper will prevail here.
Other boards have been ordered from @JLCPCB , assembled, and should be on their way here in ~3 days.
Testing using two BMP180 development boards showed good resolution and surprisingly predictable response curve. Our target sensors have about 10x that resolution so we are now extremely optimistic about how this will perform.
The 3D model matches the boards and the prints are pretty consistent. The overhang for the board area for FFF may need to be a little more gentle: at normal speeds it can get messy. Looks great using SLA.
For FFF, this was rendered out to use a 0.4mm nozzle, 0 walls, all infill, concentric. This results in a better print as then the printer only leaves the solid area once per layer to jump to the middle 'break off' support for the lower pitot tube. When I say rendered out for a 0.4mm nozzle, I mean that critical wall thicknesses are an exact multiple of the nozzle size. If you want to use a different nozzle, it would be much better to adjust the model and render again to keep this trait.
There is also the possibility of switching out to a venturi, but we would have to get creative to get the flow direction data then.
BOM for actives for I2C version:
- 511-M24C01-RMN6P EEProm, optional... maybe
- 262-BMP280 Sensor (need 4), Also can use the BMP388 for better resolution
- 584-LTC4316IMS#PBF Xlator (Need 2), one is optional for 3.3v only operation
- 998-MIC5225-3.3YM5TR (Need 1), optional for 3.3v only operation
A ventilator sensor shortage is brewing...
We are working on a version with an onboard MCU now to enable this to function as a standalone monitor for ventilator splitting, or to use this to replace an existing but out of stock sensor for ventilators.
Subproject of #COSV - Cam Open Source Ventilator