The problem with being a full-time engineer for a corporation is that they effectively own any code you write. This is a great way to gauge not only your value to the company, but the state of the company itself.
In 2001 I was working in my spare time on a Football Pool management system. I addressed my (now previous) company's (then) President to release the code to me. He said he was unable to do that because the company needed to explore any possible revenue streams. At the time I didn't know that this was code for, "Well, as we don't have any revenue streams at the moment, a piece of commercial software would be nice."
I promptly ceased all work on the code and have since thrown out the work I did. A few months later the president left the company, then the company laid off 70% of the staff (myself included)
So, I have spoken to my manager who seemed to realize that my 'project' while useful to my work in the office, is not related to the revenue interests of the company. Further, I have spoken to HR who referred me to legal. Legal said that I need to simply append my invention agreement with the necessary information. I will then make sure that the document I have on file includes this new information releasing my personal inventions.
Once that is done... Then I can talk about my little project which shouldn't be worth this much trouble.