Oak

🌳 Outdoor LoRa-GPS tracker with E-Ink display 🔑

power 18650

wireless LoRa,

sensor GPS, E-Ink

mcu SAMD21G18

bom items 82

bom cost USD $78.93

vendors 6

completed July 2022

Schedule

Good practices to continue for future projects

Add functional logical blocks in schematic to use similar circuits in future versions or other projects
Use stencil SMD soldering with SMD components only if it is necessary. Else, use a PCB assembly service.
Use minimum number of through-hole components
Check Gerber file format with the PCB manufacturer before rendering them
Check F.Paste and B.Paste layers for SMD stencil pattern
Pull out every single MCU pin as a test point for the first version of the project.
Always buy buffer number of components. Image is from the book Designing Electronics That Work by Hunter Scott.

Next iteration improvements

Make the PCB routing symmetrical for LED positions and connector slots
Ensure the length is not too long to prevent bending of the material
Use wider ventilation holes with wider spacing between each of them
Use less clearance for connector slots. Take note of finger access
Use other shapes for connector slots E.g. rounded corner or trapezoid
Use shape binder for seperation plane bends
Use a counter sunk screw head
Make the screw lug's initial length be wider to contain the screw head so that it can sink into the surface
Try a snap-fit enclosure

For next iteration

Use SMD components only on top layer for one-step manual SMD stencil soldering process
Place a writable area on the silkscreen to note down LoRa node address, PCB number, frequency or other info
Add a surface mount PCB test point for VBAT, VBUS, 3.3V, 5V, GND and SPI points.
Use a smaller SSD1306 I2C OLED display instead of E-Ink. It's cheaper and easier to source and buy.

Check with 3 PCBs to conclude whether it is a design issue or a soldering / manufacturing / assembly issue
Power it with current limiting power supply unit only. Check all the power test points such as VBAT, VBUS, 3.3V, 5V, GND.