Minimising Archive Size for source backup


I wanted to back up my source code to dropbox or similar. For even the smallest project the folder size is approx 300mb. The projects consist of bin, .vs, obj and source folders. There are also some files in the main folde for each project.

The source folder is very small itself. Is it possible to delete some of these files in other folders safely before backing them up?
I presume there would be some penalty in rebuild times later.

I was just thinking of only backing up the source folder but wonder if the other folders might also contain some necessary information regarding the current build etc.

Thanks for any tips if possible,