For kicks and giggles, I wanted to purchase a raspberry pi, and run a miner on it; bitcoin, litecoin, whatever. I have some solar panels that I want to use to run the unit during the day.

 I want to build a circuit that can take any number of solar panels and output whatever fixed voltage I want. Is it possible to do? And, would the amperage change based on the voltage change?

 One final question: I've heard that electronic devices will only pull as much amperage as it needs to operate. My brain is having a hard time understanding why a 6V LED will burn out when a 6V battery is attached to it if it doesn't have a resistor. Do electronics only pull as much power as they need or is there some special device that limits the amperage going into it?