Although looking a little ugly, I finally have a working IoT temperature sensor. I had put it down for a time, but returned to this project in January.

The board now:

• wakes from deep sleep
• measures the thermistor temperature via an ADC
• connects to my LAN via wifi
• posts a "rest" message to a Node.js server
• returns to sleep

The Rest server writes the record to a MySQL database.

This is version 1.2 of my board. Originally I attempted to get a tiny BGA part working, but in my home shop I found it difficult to assemble the board. I changed to an alternate SMT land-pattern that I've had more success with.

Initially I expected to use a DS18B20 temperature IC. I was able to implement firmware that communicated with this part, but the sensor readings were higher than I expected. I believe it was being either internally heated or possibly being effected by heat from the CPU.

I replaced the DS18B20 with a thermistor. The board was able to accomodate the thermistor in the same location as the DB18B20 and it proved to be more acurate at measuring the temperature. Should I manufacture more of these boards I will make a new revision of the board specific to the thermistor implementation, but I have 3 boards including this one that I will be able to use.

Even though it looks a bit grubby and some of the parts are not aligned this board works.

Next steps:

• Implement a web-page to display current temperatures
• Assemble 2 more boards