Dec 5, 2013 · Solar Road Stud Circuit Schematic. Solar Panel: A 3V/100 mA (0.3W) rated solar panel is used here. Such panels are widely available at a cost less than $2. Output of the solar panel (SP1) is directly connected to the re-chargeable cell (B1) through an ordinary silicon diode 1N4007 (D1). Re-chargeable battery: The power back-up mechanism is