ELPM-S3LW / Energy budget
Designing an autonomous LoRa sensor.
How we prepare and verify this contentAn autonomous node starts with energy available during the worst period, not the module's nominal current. Every cycle must include storage, leakage, boot, sensing, processing, radio and margin for temperature and ageing.
Define the complete cycle.
Write the operating sequence and measure current and duration for waiting, wake-up, sensor stabilization, acquisition, processing, radio connection, transmission, optional reception and shutdown.
Ecycle = Σ(V × Istate × tstate)
Battery and energy harvesting are not equivalent.
| Aspect | Primary battery | Energy harvesting |
|---|---|---|
| Constraint | Total energy and self-discharge | Worst-period available energy |
| Storage | Cell | Rechargeable cell or supercapacitor |
| Radio peaks | Cell internal resistance | Buffer and converter capability |
A harvester may provide enough average energy yet fail to support TX peak current. Storage must deliver the peak without falling below the module minimum voltage.
Reduce duty cycle before optimizing code.
- Transmit only when the value changes enough.
- Aggregate several readings into one message.
- Avoid unnecessary RX windows.
- Use event wake-up instead of polling.
- Select data rate and power from the real link, not the maximum available.
Measure and add margin.
Estimates must be checked through current and voltage measurements on the complete product. Repeat at low battery, temperature limits and poor radio conditions. Include self-discharge, tolerances and storage degradation.
Measure your boundary. Published ELPM-S3LW Otii traces characterize the module. They do not replace measurement of the final carrier, sensor and energy source.
Review ELPM-S3LW power architecture and bench traces.
ELPM-S3LW