Trying to use a NES Zapper as Superscope

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Fisher
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Trying to use a NES Zapper as Superscope

Post by Fisher »

Well, I know that's kind of crazy, but I tried and have somewhat succeeded.
I say somewhat because the precision is not very good, most of the time 2 shots in the same place aren't registered correctly.
These is the schematics I used:
Schematics
Schematics
And a video of the result:
VID-20220323-WA0389.mp4
Video of the stuff in action
(3.72 MiB) Downloaded 23 times
The pistol in question is from an NES clone called "Dynavision Radical", very popular here in Brazil.
Here is my try to draw the schematics:
Clone gun
Clone gun
I disabled the trigger's "turbo" function, bypassing the circuit so I could test it better and add the extra commands to it too,
Extra controls
Extra controls
Now comes the practically impossible question:
Is there a way to fix this?

Thanks in advance.
calima
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Re: Trying to use a NES Zapper as Superscope

Post by calima »

Isn't the mechanism all different? NES Zapper detecting white (or any bright light) and the SNES scope detecting the CRT pulse?
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Fisher
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Re: Trying to use a NES Zapper as Superscope

Post by Fisher »

I really thought they were completely different beasts and that in no way a zapper would work, especially because it's a clone.
But looks like it works (sort of), with problems with target precision.
Could it somehow be related to the time the signal takes to be transmitted and processed?
Maybe if I add some kind of delay to it?

By the way, I don't have an oscilloscope, but I'm really curious to know what kind of data is transmitted by the light sensor in both cases.
Maybe this can help to understand if there is a simple way to "fix" it or if I was just lucky because I used a clone gun that's slightly different from the original.
lidnariq
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Re: Trying to use a NES Zapper as Superscope

Post by lidnariq »

Fisher wrote: Sat Jul 23, 2022 7:36 am Now comes the practically impossible question:
Is there a way to fix this?
probably. There's a lot of extra complexity there - the chain of the 4049s, the resistors and capacitors - that are more complex than I think they need to be, and are probably causing the noise.

I suppose they bothered to implement an actual demodulating filter here, but the SNES (and indeed, everything but the NES) needs to not have it.

Maybe you could get away with the circuit in the modern Tomee Zap Gun, and just reuse the existing housing: viewtopic.php?p=226544#p226544
calima wrote: Sat Jul 23, 2022 9:35 am Isn't the mechanism all different? NES Zapper detecting white (or any bright light) and the SNES scope detecting the CRT pulse?
Nope. They're actually the same, other than the Zapper's filter. The Master System, Megadrive, and SNES have hardware that latches the first moment it sees light, while the NES just has to poll and the filter stretches that out vertically and adds horizontal noise.
Fisher wrote: Sat Jul 23, 2022 11:49 am By the way, I don't have an oscilloscope, but I'm really curious to know what kind of data is transmitted by the light sensor in both cases.
It's basically just high/low meaning light seen / not, or vice versa
Pokun
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Re: Trying to use a NES Zapper as Superscope

Post by Pokun »

Wow this is really interesting. I also thought they worked very differently, but I guess both types of light-guns are essentially just a light-sensor that sends a signal whenever it sees light.
The Zapper should also have some extra circuitry that checks the timing of the flash so that you can't cheat by shooting on a lightbulb though (unlike the first CRT light-guns that Nintendo made for Ralph Baer and Magnavox' Odyssey which detected continuous light just fine).
The Zapper trigger mechanism is also a bit different from the Super Scope, since it releases the trigger when you press it all the way in (since Zapper games normally looks for the trigger release edge for the shot) while the Scope has 2 modes.
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Fisher
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Re: Trying to use a NES Zapper as Superscope

Post by Fisher »

That's great!
Thanks for the information. :-)

Maybe if I just plug the photodiode direct on the 4049 pin 11 or pin 14 could fix the issue?
By the way, I've found this project from Nino on GitHub pretty interesting.
Looks like the idea of building something more or less "universal" is totally possible.
lidnariq
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Re: Trying to use a NES Zapper as Superscope

Post by lidnariq »

Fisher wrote: Mon Jul 25, 2022 6:10 am Maybe if I just plug the photodiode direct on the 4049 pin 11 or pin 14 could fix the issue?
The phototransistor or photodiode will need some kind of biasing, so that's not sufficient. I just have never built one, so I can't give you any guidance.

Certainly the Tomee Zap Gun is the simplest circuit I've ever seen.
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