Well I just got back from Home Depot... I bought a 100W metal halide light bulb, a socket, an extension cord, and a timer. I tried to screw the bulb into the socket, then plug the socket into an outlet, but the bulb won't light up... Is there a transformer or something that I need?
yup you need a ballast. if you're going to spend the $$ on HID bulbs and ballasts, you might as well get more than 100w because that won't get you very far, especially if you only have MH (because that'll only get you through the veg state, not flowering). you'll need both MH and HPS for a nice grow. my advice is to buy a 250 or 400w HPS ballast, along with a HPS bulb and a MH conversion bulb. it'll make a fantastic combination, and only run you about 150-200$ total (try ebay for example). the bulbs will last several grows, and the ballast will last as long as you enjoy the beauty of growing.
^^x2 I picked up (on ebay) a 400w HPS ballast, HPS blub, MH conversion and reflector for $125 shipped. Ebay and craigslist are best.
Hmm... I'll think I'll go with CFLs... my concern is that CFLs 100W+ are too big, and are hard to fit in a computer box.
u can grow amaising plants start to finish on MH. i would suggest more watts if thats what u wanna try... but everyone else already gave u the tip. Craigslist or ebay
Another thing, MD+ballast have 3 ends- Netural, Pos, and Neg, but my timer only has 2... What should I do?
You just need to get a 3 prong timer,Home Depot has them for less than $10. But if your doin this in a computer case and runnin CFLs you wont need one.