This solar powered vario for paragliding is an adapted from the design by Hari Nair. It includes his original solar charging of a super capacitor, with an updated pressure sensor and a microprocessor selected with the minimal pins and memory needed for the design. In addition, the USB charging circuit was removed, but can be added using the spare solar panel connector.
The original design by Hari Nair used two 6V 16 mA solar panels. There is provision on the PCB to connect two, but I am using a single slightly larger 5.5V solar panel instead. This reduces the total charge on the capacitor, but gives a slightly larger headroom to prevent over charging of the capacitor by the solar panel. The diode D1 drops the voltage by approx 0.6V or less at low current which makes it a bit to close to the capacitor voltage rating if using 6V solar panels.
The super capacitor will fit any 5mm lead spacing package. The size of 0.22F was selected to give a run time of around 15 minutes without solar access. A larger capacitor can be used if you spend a lot of time in the shade at cloud base. But only testing will confirm if the selected capacitor is sufficient for real flight. The 0.22F capacitor greatly reduces the part cost over larger sizes. Maxim has a good tool for calculating run times from capacitors (https://www.maximintegrated.com/en/design/tools/calculators/product-design/supercap.cfm)