ELPM / Energy harvesting case study
A 5 mm door sensor powered by its environment.
How we prepare and verify this contentThe prototype combined magnetic state detection, environmental measurements, indoor photovoltaics and LTO storage in an approximately 5 mm form factor. It does not prove universal autonomy; it shows why mechanics, energy profile, storage and connectivity must be designed as one system.
A door sensor can measure more than open or closed.
A Hall sensor provides door or window state while temperature, humidity and air-quality sensing turn the same installation point into a building-automation node. Every measurement adds warm-up time, energy and mechanical constraints; its application value must justify the energy cost.
Five millimetres creates system-level trade-offs.
A thin form factor constrains component height, antenna, storage, connectors and mounting. Magnet position, surrounding materials and distance from the surface affect both Hall sensing and radio performance. The aesthetic constraint therefore needs validation alongside range, assembly and robustness.
Energy harvesting means balance, not automatically battery-free.
An indoor photovoltaic cell produces variable energy with illuminance, spectrum, orientation and shading. LTO storage must support radio peaks and periods with insufficient harvest. The design is sustainable only when harvested energy, self-discharge, conversion losses and worst-case consumption remain balanced with margin.
The historical prototype and the current candidate have distinct roles.
The demonstrators shown at CES 2025 and Embedded World 2025 used the ELPM-N52-MINI platform with nRF52840, a power latch and BLE, Zigbee and Thread connectivity. They are prototype evidence, not specifications for the current range. For new energy-harvesting devices, ELPM-N54LW is OBJEX LABS' preferred candidate: the in-development nRF54L15 architecture targets Bluetooth LE 6 and a sub-GHz section for LoRa or custom protocols. Final electrical figures will be stated after validation and datasheet publication.
Validate darkness, events and difficult links.
- Measure harvested energy under real lighting conditions, not only beneath a bench lamp.
- Integrate charge and consumption over complete cycles, including boot, sensing and radio retries.
- Test clustered events and extended periods without light.
- Verify antenna and magnetic detection in the final enclosure and mounting position.
Explore the ELPM candidate for next-generation energy-harvesting sensors.
ELPM-N54LW