I found this 3rd party light gun for the NES:http://bit.ly/MxKTM9 If I plugged the receiver into the NES controller port on my RetroN 3, would I be able to play light gun games on an HD TV, or would I still need an old CRT screen, and the sensor is just for the wireless feature? Just wondering.
No, you still need a CRT.
to simplify the things and give more understanding how it works:
light gun just reads the horizontal scan lines which come from the white hit box. Then famicom counts them :) So only CRT, without other variants
Cool. Just wondering. Doesn't mean I might not stumble across a way that works. Just means that it might take a while!
I don't think HD TVs can do it at all actually, they don't have a reflective screen, which is required to register the hit.
It's not that the screen needs to be reflective, but in time with the console. When firing the NES (depending on the game) turns the entire screen blank for a frame to check if the gun isn't pointing at a bulb. Another single frame check to make sure the photo diode is pointing at the newly placed white block so it registers a hit, then it goes back to the game.
Upscalers on HDTV's cause input lag, which will throw the frame check time off thus rendering the light gun useless. Now if by chance you were able to delay the gun to the same speed as the HTDV's upscaler delay you could in theory make it work. But good luck designing the circuit to go between the gun and the console to make it work.