While researching the prior art, I found a patent filed by a large corporation and at the end of the description they say something like "an accelerometer or other sensor can be added". My idea uses an accelerometer (like the one found in almost all smartphones today). Does this affects my claim of novelty (given that whe accelerometer is just a small part of the concept)?
Yes it does - for that small part is not novel anymore. As long as the rest of the invention is novel and inventive, you are fine though. For a claim to get granted the whole claimed invention has to be inventive, not every part of it.
Example: you could patent a whole airplane with fins instead of wheels (if not known yet) even though an airplane is known and fins are known, but the combination as such is not.
Concerning the comment about the accelerometer:
A claim normally consists of two parts (actually, there is the so called two-part-form for this, don't worry, you only have to use it if the examiner requests it) the known (= prior art) part and the inventive part that distinguishes the invention from the prior art.
Let's say your invention is
A smartphone with a display and a cpu and a gpu and bluetooth comprising (this part is prior art, it's known, the following is not known in connection with the former smartphone)
- an accelerometer
- a bluetooth connected temperature sensor
- the combination used to algorithmically compute the temperature of the sun.
Now you realize that actually smartphones with accelerometers are normally used to compute the temperature of the sun, combined with different other means, but the temperature sensor connected over bluetooth hasn't been described and using it is inventive as the prior art doesn't hint towards it nor it is obvious.
Your claim stays the same, but in the two part form it would be
A smartphone with a display and a cpu and a gpu and bluetooth with an accelerometer used to calculate the temperature of the sun by
- algorhitmically including the sensed values from a temperature sensor connected over bluetooth.
For the claim to get granted, it has to be novel and inventive over the prior art. As you see, different prior art just changes the way of assessing the claim, but as long as it stays inventive, you can add as much known stuff as you want or see fit.