sensing letters in your letterbox via IR diode pair, sending out status via LoRaWan/TTN based on Attiny84, RFM95W, HSDL9100, powered by a CR2032 battery.
This is basically a clone of the heise ct briefkasten sensor project
https://www.heise.de/ratgeber/IoT-Netz-LoRaWAN-Briefkastensensor-mit-hoher-Reichweite-selber-bauen-4417179.html
https://github.com/jamct/radio-mailbox
Contents:
- ./PCB/ : kicad PCB files
- ./calibrate/ : calibration sketch to adjust the poti for letter distance
- ./letterbox_sensor/ : lora letterbox sensor sketch
- ./misc/ : payload decoder, sample http integration cgi
Compiled with platformio, hex flashed to attiny with ArduinoISP
Changes:
- created SMD PCB
- onboard 868MHz PCB antenna after TI document http://www.ti.com/lit/an/swra227e/swra227e.pdf
- switched MISO/MOSI lines of RFM95
- Attiny pin renumbering 0...10 -> 10...0
- sensor pin naming changed from 8 -> A2, otherwise no ADC reading
- added basic temperature reading from RFM95
- added sensor raw value, voltage, temperature in lora package
BOM (digikey.de):
| Part number | Description |
|---|---|
| ATTINY84A-SSUR | IC MCU 8BIT 14SOIC |
| HSDL-9100-021 | PROXIMITY SENSOR |
| RFM95W-868S2 | RF TXRX MODULE |
| 3314G-1-105E | TRIMMER 1M OHM |
| BU2032SM-FH-GTR | CR2032 COIN CELL HOLDER |
| HLE-103-02-L-DV | CONN RCPT 6POS |
| AA3528LSECKT/J4 | LED ORANGE |
| CRGCQ1206F33R | 33R 1206 |
| CRGCQ1206F220R | 220R 1206 |
| LQG18HN1N8S00D | IND 1.8NH 0603 |
| GRM1885C1H2R7CA01D | CAP 2.7PF 0603 |
Have fun!