The SLAPS Solar Harvester is intended as a the first step into solar power collection and management. While previous iterations in the SLAPS family have focused on solar panel deployment and configuration, the solar harvester focuses on collecting and managing the power generated by four solar panels. The primary device enabling this functionality is the AEM10941. This power harvesting IC collects power from the panels, regulates the power to multiple useful voltage levels, and charges a storage unit. This design required minimal passive components allowing for a low cost and space efficient design. In addition to the power harvesting circuit, the solar harvester will also feature a RP2040 microcontroller, altitude rated pressure-temperature sensor, and NAND flash for data logging. These additional components will provide an adequate test for the harvester capabilities. In order to leverage the space efficient nature of the electrical configuration, the structural construction of the solar harvester focuses on tight tolerances using 3D printed components. Maximizing the space efficiency of the solar harvester improves aesthetics and maximizes the flight line configurations that the solar harvester can fly on. Overall, this design will provide a realistic and maximally space efficient test of a solar harvesting circuit that could potentially be used in future SLAPS iterations.
The AEM10941 features multiple preset configurations as well as a custom mode. In this design, the configuration profile 111 is used by pulling the three configuration pins high. This configuration is designed for use with a Li-ion battery as the storage source and 3.3V and 1.8V outputs. The decision to use a Li-ion battery primarily comes from the need for a 3.3V output.
Quiescent current is expected to be roughly [0.6 \ \mu A](tex://0.6 \ \mu A) at a battery voltage of roughly 3.6V. The efficiency of the linear drop-out regulators are as follows:
- High-voltage: 80-90%
- Low-voltage: 70-80%
Overall, the losses experienced in the AEM10941 are relatively low in comparison to the power consumption of the device as a whole.
The RP2040 microcontroller is an incredibly popular Arduino compatible microcontroller with excellent design resources.
The MS560702BA03-50 barometric pressure and temperature sensor designed to operate from 10 to [1200 \ mbar](tex://1200 \ mbar) and -40 to [85 \ \degree C](tex://85 \ \degree C). These values fall within typical launch conditions and this sensor should be able to provide barometric pressure and temperature values accurate to [\pm 2.5 mbar](tex://\pm 2.5 mbar) and [\pm 0.5 \ \degree C](tex://\pm 0.5 \ \degree C) for the duration of flight.
At a 3.3V supply voltage the MS560702BA03-50 has a peak power consumption of [4.62 \ mW](tex://4.62 \ mW) and a standby power consumption of [0.07 \ \mu W](tex://0.07 \ \mu W). Peak power consumption is unlikely to occur and typical power consumption at 1 sample/sec is expected to be less than [42 \ \mu W](tex://42 \ \mu W).
The solar harvester features one energy storage unit in the form of a single Li-ion battery cell.