I am trying to make a studio light that will have 12 segments. Each segment will look like this:
(10 LEDs (3.2v, 20mA), 2 connected in series then parallel to each other segment, 5 150 ohm resistors, 9 volt battery for mobility)
I plan to connect multiple batteries in parallel to achieve a constant voltage and accumulate current to power the LEDs for a longer period of time.
I've tested a single segment of this circuit and I am impressed with the results. What I want to do next is connect a Raspberry Pi to the circuit. I have not posted this on the Raspberry Pi forum because this question is geared more towards the actual electronic components. I understand that I need a component to connect the LEDs to the micro controller. I was thinking about using some sort of transistor or relay, but I have no idea how to pick the appropriate one.
Another problem arises because I am using 9v battery that will connect with a 5v circuit. I know some transistors require a common ground, and I do not know how else to connect it. I've found another answer here: Creating a common ground. I am unsure if the Raspberry Pi will be damaged by doing this.
To the point: How can I control multiple segments of lights with the Raspberry Pi.