Small and easy to build MySensors temperature and humidity sensor based on BlackCircleSensor.
To be able to use the arduino with a coin cell battery, some steps are needed:
- Burn 1MHz ATMega328P 1MHz Bootloader with 1.8V BOD from MiniCore.
- Unsolder on-board voltage regulator and power LED (You can keep the built-in LED in pin 13, it's useful for debugging).
For this sensor I used the 5V variant of the Arduino Pro mini, but the 3.3V one should work as well (Maybe even better!).
- Modify the provided sketch to your liking (Static node id, battery level reporting...).
- Upload the sketch to the Arduino without the coin cell battery inserted.
- Unplug the Arduino from the FTDI cable and insert the battery.
| ID | Name | Designator | Footprint | Quantity |
|---|---|---|---|---|
| 1 | Male header 1x10 | J1 | H10-2.54 | 1 |
| 2 | CR2032 holder | B2 | CR2032 SMD HOLDER | 1 |
| 3 | Capacitor 10uF | C1 | CAP5X7 | 1 |
| 4 | Capacitor 220uF | C2 | CAP-D6.3XF2.5 | 1 |
| 5 | Arduino Pro Mini | U1 | ARDUINO_PRO_MINI | 1 |
| 6 | SI7021 | S1 | SI7021 MODULE | 1 |
| 7 | AS01-ML01S | MK1 | NRF24L01_SMD+ | 1 |
You can download the Gerber files here.