I don't know how much the sentinels will factor into X-Men: Days of Future Past.  Bolivar Trask's mutant-killing giant robots will wreak havoc in the future, but a majority of the film will take place in the 1970s with Wolverine (Hugh Jackman) and the First Class characters trying to change history.  Undoubtedly, the sentinels will be a big (no pun intended) factor in the marketing campaign, and we've seen them in set photos, propaganda posters, and now a blueprint detailing the heads of the mechanical monstrosities.  If you were wondering where the "activator" is, it's in the neck.

Hit the jump to check out the full blueprint.  X-Men: Days of Future Past opens in 3D on May 23, 2014.

Via X-Men Movies.  And click here for a full size image of a Sentinel next to director Bryan Singer.

x-men-days-of-future-past-sentinel-blueprint

Here's a description of the sentinel program from the Trask Industries website:

In 1973, Trask Industries introduced the first Sentinel production model, the Mark I. Bolivar Trask’s groundbreaking research in AI, robotics and autonomous ballistic systems laid the foundation for the world's most capable anti-mutant defense system. Since the program's inception, we’ve continued to advance our founder's cause through eight additional generational upgrades and enhancements.As we celebrate five decades of achievement, we also bid farewell to regular production of the Mark I and shift our efforts to full-time manufacturing of the Mark X — our first complete overhaul of the Sentinel line. These highly anticipated units will combine next-generation nanotechnology and bioweapon breakthroughs, promising an even brighter future for the human race.