Parts: RAK4631
RAK19007
RAK1600
Meshtastic firmwear 2.5.6
(Android 2.4.4)
Can one prevent the RAK from going to factory settings after brownout by using a supervisory circuit MCP120-315 connected to the pins of the RAK4631 ?
In field tests using deliberately poor illumination, the RAK radio in the layout below often (but not always) adopts factory settings following brownout. That means: when the battery is so empty that the RAK radio switches off, then when the battery is re-charged sufficiently by the sun, the RAK4631 does not come on with the previous settings but adopts the factory settings, and needs to be re-programmed/set manually using e.g. Bluetooth and the app e.g. the region (frequency) and so on. This results in the device being problematic as a solar node for leaving unattended and/or inaccessible due to needing the parameters to be re-set/entered manually merely for the radio to join the Mesh again when the sun has done its job in charging the battery.
I was wondering if the use of a supervisory circuit D connected to the RAK4631 pins as shown in the circuit below would help by keeping it in reset (low) until the voltage is a decent 3.0 V for a decent time (this being a good charge voltage for the LiPo battery). This was suggested by a colleague and is not dissimilar to the solution suggested here https://forums.adafruit.com/viewtopic.php?p=809049#p809049 .
Circuit
Device
Parts
A: Solar panel: Solarzelle - 2W, 6V, 11.0 cm * 13.6 cm Solarzelle - 2W, 6V, 11.0cm*13.6cm günstig online kaufen | Funduinoshop
B: 2000 mAh LiPo Lithium Ion Battery - 3.7V 2000mAh : ID 2011 : Adafruit Industries, Unique & fun DIY electronics and kits
E: radio RAK4631: Nordic nRF52840 Sound Detector IoT Audio BLE Core LoRaWAN Module
F: RAK 19007 base board RAK19007: WisBlock Base Board 2nd Gen With USB type C connector & GNSS modules
C: Thermal switch: Bimetallic Thermostat switch for 55 degrees C sourcing map 10 Stücke Temperaturschalter Thermostat Bimetall 55C Normal Geschlossen KSD9700 : Amazon.de: Baumarkt
D: Supervisor circuit, open drain, reset low, MCP120-315GI/TO https://ww1.microchip.com/downloads/en/DeviceDoc/11184d.pdf with a trip voltage of 3.0 V to 3.15 V
B: Battery solar charger: Hailege CN3065 Mini Solar Lipo Charger Hailege 2pcs CN3065 Mini Solar Lipo Ladegerät Board Lithium Batterie Ladechip Micro USB DIY Outdoor Application Kit Ladebrett Modul : Amazon.de: Elektronik & Foto
which appears to be this device in this video CN3065 18650 Li-ion Mini Solar Charger Module - ThinkRobotics – ThinkRobotics.com
which implies the maker is IoTMCU and described here GitHub - IOT-MCU/Solar-Charger-v1.0: Solar Charger v1.0 with this circuit diagram
Solar-Charger-v1.0/Solar Charger v1.0.pdf at master · IOT-MCU/Solar-Charger-v1.0 · GitHub
**Any feedback / improvements welcome about this plan, or reports of alternative or similar solutions. **
Thanks.