This is a small electronic project for a flashlight that runs on solar energy by charging a battery.
- the capacitors are decoupling capacitors, they are used in parallel with voltage regulators almost always;
- the schottky diodes prevent current from returning to the solar panel. I chose schottky because it has a low resistance and most similar circuits use it too. The ones I used are oversized as I didn't have others, but the 5817 would work just fine;
- the switch have 3 positions: (I) light, (0) off, (II) charging;
- this solar panel produces 7 volts and delivers around 130mA under the sun in clear skies;
- the plastic box (aussie: "jiffy") is too big for this but it was the only one I found that fit the solar panel;
- the battery is a 3.2V rechargeable LiFePO, so you can turn on the LEDs without the need for resistors. The LEDs are white high-brightness 3.2V 30mA;
- the central part of the circuit is the regulator LM317 adjustable from the trimpot;
- 3.2V LiFePO batteries are charged with a maximum voltage of 3.65V, as seen in (learnmetrics.com/lithium-life...) so I regulated from the trimpot at 08:45;
- the circuit is at 08:13.