Open Source Wireless Environmental Sensor HW, Part 6: Testing the prototypes
- Part 1: Introduction and Requirements
- Part 2: Prototyping
- Part 3: Design
- Part 4: Schematics, PCB and PCBA
- Part 5: Production
- Part 6: Testing the prototypes
In our previous articles (links can be found above) we introduced our wireless environmental sensor project; which is a rechargeable battery-operated wireless sensor that can measure:
- Temperature with ±1.0°C accuracy
- Barometric pressure with 1 hPa absolute accuracy
- Humidity with ±3% accuracy
In our previous article, we talked about how we produced our prototype boards. In this article we finally get to see the board, here we go:
First boot, tears of joy 😂
I was so happy when I connected the board to my laptop and the serial port popped up at once!
Just being able to connect to the board felt like a huge victory (last time we did a design, although much more complex than this design we failed…). I was a bit worried that we messed up the automatic bootloader functionality. Luckily everything worked as plan!
I used the following source code to test the boards; I almost cried when I saw the temperature, air pressure and humidity values 🙌. During the first attempt, I did not connect a battery to the board. After I concluded that the BME280 design worked, I wanted to try the battery monitor; I connected the battery to the board and I got the battery level!
Whoo Hoo!!!
Things went south, tears of sadness 😭
At this stage, I was very happy that everything seemed to be working but unfortunately, it only took a few minutes to realised that I made some minor mistakes. All LEDs on the board were not controlled by the ESP32… not a huge impact but still annoying.
And then I got an even bigger surprise!
🔥
The board gets really hot!
And this, unfortunately, heats the BME280, the temperature reading is off by several degrees. 😭
What happened?
Basically, copper is really good at conducting heat, because we have a solid ground plane between the ESP32 module and the BME280 we get an undesired heat transfer…
How do we fix this?
It is best to avoid copper planes near the BME280 that are connected to the ESP32 (the heat-generating IC). The picture below shows the approach that we plan to use in the next revision to fix the issue. We will also try to move the BME280 further away from the ESP32 and most likely make the board twice the size (to increase the distance and spread the heat).
Summary
We are the first company in Sweden to get their hardware certified as
Joining cool companies/projects such as Arduino, BeagleBone, Adafruit, Olimex just to name a few!
But we need to create a new revision of the board to feel really proud… but first, we need to do a bit of software development. It is likely that the software will place new requirements on the hardware. The hardware is good enough to do some initial software development, which is something we are going to do the coming months.
Stayed tuned!
Thank you for reading! Take care and hope to see you soon. 🙏🏽
This article is a living document please reach out to me if you want to contribute or see anything inaccurate here. This article is part of our “Boosting Innovation” project.
