5. Packaging and Test Chamber¶
5.1. File Download¶
COM case Fusion 360 file
COM cover STL file
COM base STL file
EFC case Fusion 360 file
EFC cover STL file
EFC base STL file
Test chamber dxf file
For packaging, I made two 3D models and used 3D printing. Each case has a base and a cover. The base is where the board and other components are fixed. The covers are designed to show visual messages and enable controls. Parts were printed such that support needed is minimal.
| Part | Filament gm | Print time |
|---|---|---|
| COM cover | 57 | 6 hours 15 minutes |
| COM base | 66 | 7 hours 20 minutes |
| EFC cover | 56 | 6 hours 0 minutes |
| EFC base | 61 | 6 hours 48 minutes |
5.2. Carbon Monoxide Monitoring Unit (COM)¶
The cover has cuts for the LCD, CO sensor, buzzer, control push buttons and LED module. It fits the height of components inside. I used Eagle PCB file to get the right position of each component reference to board boundaries.
The base has extrudes with 3 mm holes where M3 screws are used to fix the board. A special extrudes also added to keep the NRF24L01+ wireless module in place. It also has cuts for power jack and ventilation. I exported a dxf file from Eagle for board boundaries and hole positions, and used in Fusion 360 to build the base.
The image below shows the board put inside the COM base.
5.3. Exhaust Fan Control Unit (EFC)¶
The cover has cuts for the LED module. It fits the height of components inside. I used Eagle PCB file to get the right position of each component reference to board boundaries.
The base has extrudes with 3 mm holes where M3 screws are used to fix the board and the 4-pos terminal block. A special extrudes also added to keep the NRF24L01+ wireless module in place. It also has cuts for power jack and ventilation. I exported a dxf file from Eagle for board boundaries and hole positions, and used in Fusion 360 to build the base.
The image below shows the board put inside the EFC base.
5.4. 3D Printing¶
I used Ultimaker 2+ printer and PLA filament with settings below.
Quality
Layer Height: 0.20 mm
Line Width: 0.35 mm
Shell
Wall Thickness: 0.7 mm
Top/Bottom Thickness: 0.6 mm
Infill
Infill Density: 40%
Infill Pattern: Zig Zag
Material Printing Temperature: 200 °C
Build Plate Temperature: 60 °C
Speed
Print Speed: 45 mm/s
Travel
Enable Retraction: Yes
Cooling
Enable Print Cooling: Yes
Fan Speed: 100%
Support
Generate Support: Yes (Everywhere)
Build Plate Adhesion
Build Plate Adhesion Type: Raft
The image below shows printing orientation for each part.
5.5. Test Chamber¶
The test chamber is made using laser cutting and 3 mm transparent acrylic. It is used to test the system by creating a closed chamber where CO levels are raised by burning cotton soaked with liquid fuel. The chamber dimensions are W x D x H = 200 mm x 150 mm x 100 mm.
