This is the circuit drawing, it has been revised several times. It will run a whole year on 2 D batteries, cheapo Dollar store batteries price $1 for 2 batteries. Circuit will not run when voltage gets below 2.8v. LEDs are the limiting factory for higher voltage. 4.5v makes very bright LEDs. I learned the trick to bright LEDs on 3.3v is 100uf caps holds a larger charge than 50uf or 10uf caps. LEDs are easy to see after dark 400 ft away with 3.3v.
When battery voltage drops to 1.35v each battery put 3 used batteries in series = 4.05v the circuit will run about 7 to 9 more months.
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