Archiving data is one of the last phases in the research lifecycle. Here are a few things to keep in mind during your research project
If your data is not useful or understandable, then perhaps it should not be archived. If there is any confusion, it is always best to speak with the staff at the data archive or repository you have selected. They will be able to review your data and documentation to better inform you of your archiving and preservation needs.
Here are a few repositories dedicated mainly to science and engineering.