How does the Nintendo Light Gun work? (with video)

Filed Under Video Games on 2006-10-29, 17:05

Ahhh the old Nintendo Zapper, aka the Nintendo gun. An object of great joy and entertainment from our childhood. Something we played with day in and day out, but most of us had no clue how it worked. We’d make up stories about it shooting lasers off the tv or it changing the TV screen so that it knew where the gun was pointing, and accepted one of these highly uneducated explanations and continue with the game of Duck Hunt on the old NES, wondering why we could never shoot that stupid dog when he laughed at us.

In the past I’ve read explanations about how the Zapper actually worked, but that wasn’t enough for me. I wanted to see what was inside that plastic shell. So I found some tiny screwdrivers, exacerbated my mild carpal tunnel removing them and managed to get the thing apart. But before we get to the gory, err geeky pictures, a quick explanation for those that are still curious about how it works.

No, the gun does not shoot light. In fact it receives light. When you pull the trigger, the video game quickly changes the screen, so fast that most people don’t even notice it. By using the alterating of color and white light from the tv, the gun uses a photodiode to detect whether it’s scored a hit or not. So in short, the gun decides if you hit your target, not the Nintendo system. Here’s a brief explanation from Wikipedia:

When the trigger was pulled, the game blanked out the screen with a black background for one frame, then, for one additional frame, drew a solid white rectangle around the sprite the user was supposed to be shooting at. The photodiode at the back of the Zapper would detect these changes in intensity and send a signal to the NES to indicate whether it was over a lit pixel or not. A drop followed by a spike in intensity signaled a hit. Multiple sprites were supported by flashing a solid white rectangle around each potential sprite, one per frame.

So, with that said, here’s the picture of the gun mostly dismantled. Click on the image to jump to flickr to see the parts identified.

And here’s a video of what’s happening inside with that familiar “pang!” when you pull the trigger:

Tagged: Light Gun, Nintendo

Comments

Byteme

If it used a frame for each target the game would flicker like made, seek here for your answeres:

"Most light guns depend upon the way a TV display is actually drawn in one spot at a time--the dot being displayed scans from left to right very fast line by line from top to bottom."

"The light gun itself merely has a light sensor "aimed" directly in front. By detecting the timing of the signals it receives, the game console can deduce where it's pointed. (Some calibration is required due to differences in time delays depending upon the exact TV or CRT projector used.)"

http://arcadecontrols.com/Archives/messages/370...

In effect, LCD and plasma are all out when it comes to using this tech.
Byteme

LOL...

I read two more lines down where they say exactly what he said... Nintendo Zapper worked with the white boxes, 1 per target per frame...

And come to think about it the game really did blink like mad(e)!!!!

Anyone else remember duck hunt being uncomfortable as hell to play?
Brandon

He explained how it hits multiple targets. So for the first frame (30 frames per second), the system draws a black screen. Then, for the first target, a white box is drawn around it. In the next frame, the next target will have a white box drawn around, and the first target will just be black. So at any point, if the gun is pointing at one of these white boxes, it will register a hit. The nintendo knows which box is hit, because only one box is drawn on the screen at any given time...with all of this happening on the order of milliseconds
Monica

I have Same question that Ricardo Posted... how does it works???!!!
Ricardo

didn't understand how can the gun differenciate between multiple targets. If you have two ducks on screen how the gun knows which duck am i shooting. Do they have different light intensity or something like that?
mita

article help me so much
thanks :)
Mike Goysovich

This was an imformative article. Sweet!