What should I do if my advisor won't give me input into my own projects?
I don't say this lightly, but it's in your best interest to switch labs. I think you know that already but it's a soul-crushing reality to face. Let's face it now, before it's too late.

I had many friends throughout graduate school in similar situations, and the spectrum of outcomes is telling. The students that stayed in their labs despite functioning primarily as a technician were miserable, for years, and fundamentally deprived of their opportunity to grow as a scientist. None stayed in science or academia. The students that joined new labs had a better idea of what kind of mentor they wanted to work for, were happier, and universally wished they had left sooner.

You are likely thinking to yourself:

1) You've done so much work already! How could you possibly start over? 


I know, it stinks! But your job as a graduate student is to become an independent thinker, not push through projects already defined for you. Plus, you're not really starting over. You're TAing, doing coursework, learning to program, and hopefully learning how to assess the literature. You'll continue to build on all those skills.


2) You're still a junior member of the lab! As a senior more experienced student you'll get more freedom!


Advisors that promote independence establish that environment for their students early on (like first thing!). Based on what you've said, I don't think there's much room for growth.


3) You just have to talk to your advisor about your frustrations and maybe he'll give you more latitude.


I wish it worked that way. What I think you'll get is some small concession, enough to keep you hooked and doing his work. My pessimistic sense is there are very very few, if any situations where an advisor will have a change of heart adequate enough to improve your lot in lab. What you describe is a clash of philosophy: advisor knows best vs. allowing students to grow, make mistakes, and even deviate from the original trajectory. It's not that your advisor is a bad scientist, or a bad person, it just may be that he or she is better off running a lab of technicians rather than graduate students.


4) Your brother's advice: you just have to work harder!


I have to respectively disagree with that. As above, I think this is fundamentally a philosophical difference between what you want out of your education and what your advisor wants out of a student. No amount of hard work will change that.


5) This material is really interesting! There's nothing else I'm as excited about.


If the material is awesome, it makes it harder to leave. Nevertheless, I think you'll derive much greater satisfaction with a mentor who treats you more as a colleague than as a peon. 


Lastly, I think your situation portends even more dire consequences down the road. This sounds like the advisor who you might have authorship problems with, who decides you need to stay another year after publishing 4 papers, or who doesn't write you the best of letters (how can he/she if you never demonstrated your full potential?).