After publishing a blog post on the hardware of the AVAN CT-OS Open-Source DIY Reader, it crossed my mind that a DIY reader w/o a 3D printed enclosure wouldn't be complete. So I decided to design a nice case for the reader and give it a try myself!
In this post, I will provide detailed instructions on how to assemble the whole thing. I will share "stl" 3D design files at the end of my post.
Note: this is an open-source DIY project, but we also sell the assembled reader (only soldered breakout board w/o 3D printed enclosure). If you're maker and like electronics, I will strongly recommend that you buy the components and assemble the reader on your own. You will enjoy working on this project a lot! You can use the DIY reader with any of our professional research-grade sensors. You'll find the sensors in our online shop.
Happy making & tinkering, and please continue reading!
What You Need
Here's a list of what you need to get started:
3D Printed enclosure (details below)
M3x8mm screws (x4)
M2x8mm screws (x2)
28 or 24 AWG wire
Please read this blog post on how to put together the hardware of the AVAN CT-OS Open-Source DIY Reader. We also carry the assembled unit! Please visit our products page for more information.
3D Printed Enclosure
The 3D printed case enclosure has only two components: container and lid. The two are screwed together using two M3 (8 mm long) screws. I have put the zipped "stl" files for the 3D design on our download page (DIY Project Files > AVAN Zero-OS Interface > 4_AVAN CT-OS_3D_Case.zip). You can use the design as is or modify if you like.
You can print the design using PLA or ABS filament. PLA works just fine, but you need to be careful not to leave your reader under the sun or in your car during hot summer days, or it might deform or even melt! If you have a 3D printer that can print ABS filament, please use the following settings to achieve the best results:
Material: ABS
Layer height: 0.25 mm or finer
Infill: 80%
Brim width: 8 mm
Print speed 40 mm/s
Printing temperature: depends on filament brand (220 °C, default)
Build plate temperature: 100 - 110 °C
Assembling Stages
Assembling the reader is done in a few simple steps that I will explain below:
Step 1. Prepare and attach on/off switch
Start by soldering two pieces of wire (28 or 24 AWG;10 cm long) to the switch. There are two holes in the front panel along with an opening for the micro USB receptacle connector (explained later) right between the two. The hole for the switch is larger (12 mm) so it's impossible to insert it in the wrong one! Tighten the screw and you're done with this step.
Step 2. Connect panel-mount micro-USB receptacle connector to micro USB adapter
Of all the steps, this is the tricky one. You need some good level of soldering skill to get through this stage. At least four pieces of wire (28 AWG works best) are required to connect the two. You can do this without any schematic or wiring map. Plug the adapter (on the right hand side) into the receptacle connector (on the left hand side) and use a multimeter to determine which pins should are connected and solder wire to corresponding pins.
If you believe this is too much work, alternatively you may buy this panel-mount USB extension cable from Adafruit (or something similar) and fit it into the case somehow. You might need to modify the enclosure to accommodate its specifications.
Another solution is to simply use a micro USB cable (usually used for charging pones or tablets), connect one side to the reader and leave the rest outside.
Step 3. Attach the micro USB connector (extension) to the board and enclosure front panel
As you can see in the picture below, the micro USB adapter is connected to the board (Adafruit Feather M0 board), and the panel-mount receptacle connector is attached to the enclosure front panel. Use two M2 (8 mm long) screws to make sure the connector stays in place!
Step 4. Connect stereo jack
Attach the stereo jack to the front panel and tighten the hex nut that comes with it. If you found it difficult to turn the jack with all the wires attached to it, de-solder them first, take care of the jack and then re-solder them. Easy peasy!
Step 5. Solder on/off switch to the board
Now solder the switch wires (white wires in the picture under the DurUntash logo) to the back of the board. A mini slide switch is already soldered in the same holes so just use a bit more solder. You could remove the mini switch if that would make soldering the wires easier.
Step 6. Attach li-ion battery
Now attach the li-ion battery to the board and place it at the bottom of the enclosure in the corner. You can use a piece of double side tape to make sure it stays in place.
Step 7. Screw the board to the enclosure
You will find four screw holes on the board, one of which is under the OLED display and therefore not accessible. Use two or three M3 (8 mm long) screws to fix the board to the case.
Step 8. Attach the lid
Now attach the lid and fasten the M3 (8 mm) screws.
Congratulations! You took all the steps and successfully finished assembling the AVAN CT-OS handheld reader.