Some months ago, my employer told me it would be nice if the devices we develop would have 4G network compatibility. These devices are quite old now and need newer options for data transmission. I am bringing this idea to reality all by myself and my employer is quite happy about it.
I want to be obviously at a higher economical position than before once I finish this project. My employer has never talked about an economical reward once the project is finished, neither have I asked him about my reward. This is not an easy project and I'm the only programmer here. I don't want to do this "free of charge" just because I'm a programmer, and I am employed here.
How should I let him know that I want to negotiate how much money I'll get out of this project? What would be the most ideal and realistic money offering for this kind of project? A percentage share of all devices installed monthly, or a one-off big payment?