How to cut down the Voltage???
I have another newbie question that I think you can help me out with.
OK so go easy with me since I'm a beginner. . .
So, I have a laser/light (from walmart) that takes three 1.5 volt batteries that gives it a total of 4.5 volts. So, I want to hook it up to USB cable. Now, a USB cable supplies about 5.1 volts. How do I drop the current from 5.1 volts down the 4.5? How could I use the same principle in my other projects? Say I have a 9v battery and a 3.4v buzzer. I know how to use resistors with an LED. [R=V1-V2/mAH] Since I know the mAH of the LED, then I know what resistor to use. But how use that equation if at all on other things??