[u]Here is a transistor driver circuit[/u].
A transistor is probably best because a transistor will turn fully-on (saturate) with 0.7V. (A Darlington transistor is two transistors in one package and it takes 1.4V.)
A "logic level" MOSFET requires 5V and a regular MOSFET requires 10V or more.
Do I need to connect both grounds togther and to the transistor or mosfet.
Yes. Voltage needs a reference. If you put a voltage on the base of a transistor or gate of a MOSFET, that voltage "does not exist"* unless it's referenced to something (such as the transistor's emitter or the MOSFET's Source). It's the Base-Emitter voltage that turns the transistor on.
Where can I look up datasheets
If you know the part number, Google. If you don't know what part to use, browse the websites of good suppliers. Jameco, SparkFun, and Adafruit are good hobbyist suppliers. Digi-Key and Mouser have "almost everything" so it's difficult to browse but you can search/sort transistors by Collector-Emitter current, etc. All good suppliers will have datasheets on their website or they will have links to the manufacturer's website.
and learn electronics should i buy another book? Take another college class with a drug addict teacher that doesnt really want to teach?
I'm sure there are some good tutorials but I can't recommend one because I studied electronics a long time ago (in high school and college). The BEST way to learn is almost always to take a class. ...I'm sure you can learn brain surgery on the Internet but I've never heard of a doctor who didn't go to medical school. I've known one electronics engineer and one programmer who didn't go to college. The programmer was really good and very smart, but he didn't have a great job for a good company.... I've known a few programmers (with good programming jobs) who majored in other sciences, engineering, or math.
I'm not saying you can't learn on your own (plenty of people do), but it's not easy!
I took a couple of programming classes in two different programing languages, but I taught myself C & C++ (from books). But, I'm not an expert programmer and I've only occasionally programmed as part of my job.
Anyways so I am trying to save money I want to remove my arduino and use a metronomes sound or trigger (havent probed that yet) and use that to activate the transistor and/or MOSFET
With either method, you'll probably need something to "time-stretch" the trigger pulse. Maybe an NE555 chip or something similar. A microphone will need a preamp and a line-level or headphone-level signal may also need a preamp.
- Birds sit on uninsulated high-voltage power lines all the time and they don't feel anything because there is no reference and nowhere for the current to flow. You could safely hang from a power line too as long as you don't touch ground at the same time.