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It won't waste heat if you use only the needed input voltage, not more. Excess voltage will be converted to heat. Too much heat in the LM317 means too much input voltage.
Arduino UNO As AtMega328P Programmer
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High Power LED Driver Circuits
Making a Breadboardable Pinguino
Burning the Bootloader on ATMega328 using Arduino UNO as ISP
wire craft - dragon
How to Build an 8-Bit Computer
Mechanical CPU Clock
Mood Lamp with Arduino
Origami Cube Led Mood Lamp
My version of beauty
How to make your own Arduino board