It is quite clear that my smart home project is going quite slow. It is not that I spent a lot a time on it, but that I have been pretty busy with other life things. But it is moving again now.
Motion sensors assembly
Once I settled on the type of motion sensor and case, I designed some sensor PCBs . I made a small assembly run of eight sensors just to see how things will scale up, after assembling one from start to finish to double check everything works. The sensors are powered from 2 AAA batteries through a charge pump. All right, let’s go through the assembly run
All components ready
LEDs, switches and headers
Antenna with leftover holder wire
Programming bootloader and code
Drilling and finishing case
Motion sensor wires soldered
Glued in case and soldered to the PCB
You came to the wrong neighbourhood
Results and time analysis
Although I missed the opportunity to video this assembly run, I did in fact note the times required for various components. All in all, the assembly took 36 minutes per sensor node, with the time distributed as follows:
- The total time was almost 5 hours, split across 2 evenings.
- One of the modules appeared dead – non responsive and needed fixing.
- This is the ‘1 debug’ that gets accumulated with the programming time, as I could only notice the dead module at that time.
- Surprisingly, the small components (passives, LED, USB, connectors, switches) are taking a significant amount of time.
In this design, I used a ready-made mass storage USB bootloader which gives me the possibility to program the nodes from any computer. However, I found this functionality is not particularly useful … it seems easier to bring nodes to the computer than the other way around, since they can easily be moved. But for deployment with a third party, it would be very useful to program the nodes without the need for special hardware. The question now is…. OTA bootloader ?