Battery and Power
A device on a battery protects itself: it sends less when the battery runs low, turns its radio off before the battery is empty and runs again once it recovered. You set these values once in HydroNode and the device keeps them. HydroNode shows what the device runs and whether it took your change.
USB, battery or battery and solar
Tell HydroNode how the device is powered: in the device builder (Power step) or in the sensor settings (Pressure and battery). A device on USB has no thresholds, only its send interval. With a battery you add its type (LiPo, Li-ion, LiFePO4), the cells in series, the capacity and the charger.
The device has to measure its battery. Any of these works: a voltage divider on an ADC pin, a fuel gauge (MAX17043, MAX17048, MAX17049, LC709203F, BQ27441) or an INA219, INA226 or INA260 that counts the charge. Gauges sit on I²C. The LC709203F, the BQ27441 and charge counting need the battery capacity.
Four values in volts per cell
| Value | Below it the device | LiPo | Li-ion | LiFePO4 |
|---|---|---|---|---|
| Save below | sends half as often and skips gas and dust sensors. Back to normal 0.15 V higher. | 3.50 | 3.45 | 3.10 |
| Radio off below | sends one last round, turns radio and outputs off and only checks the battery. | 3.30 | 3.20 | 3.00 |
| Standby below | sleeps as deep as it can and wakes once an hour. | 3.20 | 3.00 | 2.80 |
| Resume at | runs again after two good readings at least a minute apart. | 3.60 | 3.50 | 3.20 |
The rules: Standby at least 0.05 V below Radio off, Radio off at least 0.05 V below Save, Resume at least 0.10 V above Radio off and at most 0.40 V above Save. On a pack with more cells the device works with the pack voltage, so the gaps count for the whole pack. A reading that fails never sends a device into standby; three failed readings in a row turn the radio off.
While the device waits for the battery, the sensor shows Low battery standby instead of offline. You hear about it like about an offline sensor, and again when it is back.
Send to device and the colours
The box On the device in the sensor settings shows the send interval and the four thresholds. Change them and press Send to device: the change becomes a job in Fleet. The owner and admins of a shared sensor can change them, everyone else sees them.
| Colour | Meaning |
|---|---|
| Green | The device runs these values. |
| Yellow | Saved, waiting for the device. It takes them with its next contact. |
| Red | The device refused the change. The reason is shown, Send again tries once more. |
| Blue | The device runs other values, for example after a reset. Use device value keeps them. |
| Grey | The device reports its values but cannot take new ones, or has not reported yet. |
| Device | How new values arrive |
|---|---|
| HydroNode firmware 0.8.0 or later | As a config update over the air, like any change in Fleet. |
| Your own sketch with HydroNode-Library 1.8.0 | In the answer to its next values, when the sketch uses onSettings(). |
| HydroNode station, firmware 2.1 | As a downlink after its next uplink, once downlinks are on (below). |
| ESPHome 0.5.0 | Reports its power: block only; change the YAML to change it. |
Let HydroNode send to your stations
HydroNode sends new values to a station through your network server. Set it up once in Profile, next to the LoRaWAN webhook. The box appears once you have a webhook token. Downlinks stay off until a test worked.
- ChirpStack: open API keys, create a key for your tenant and paste it. Enter the address of your ChirpStack server, for example https://chirpstack.example.com, and pick REST or gRPC-Web.
- The Things Network: in your webhook, enable the downlink API key. The key arrives with the next uplink, there is nothing to paste.
- Press Test. HydroNode looks up one of your stations. When the test is green, turn downlinks on.
- In Fleet, open the station and press Change config, or use the sensor settings. One station at a time; LoRaWAN takes no bulk changes.
The station acknowledges a change and reports its values right after. If it does not answer within six uplinks, HydroNode sends the change again, three times at most. The token is stored encrypted and is never shown again.
More: Device Builder, Fleet and Over-the-Air Updates, LoRaWAN guide.