Japanese Arcade Joystick Adapter

A place to discuss everything Dragon related that doesn't fall into the other categories.
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Bosco
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Re: Japanese Arcade Joystick Adapter

Post by Bosco »

sorchard wrote:Do you mean artwork beneath a polycarbonate or acrylic cover?
Yeah, I was thinking along those lines.

There are places now where you can get artwork printed onto sticky-back vinyl. If my new game turns out ok I might theme the panel to the game, like an 80's coin-op? :D

Need to create some space to work in the garage first though. :(
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Bosco
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Re: Japanese Arcade Joystick Adapter

Post by Bosco »

A user on the Dragon FB group requested a diagram so I thought I'd post it on here as well.

As you can see it's extremely basic and does not prevent a short occurring if both switches on the same axis close simultaneously. This shouldn't happen under normal operation but is technically possible.

I should say, I'm a total beginner at electronics and this is about the peak of my abilities. :oops:

Can anyone tell me what would happen if the circuit shorted out, how much current could it draw? Also are there any simple modifications, (like adding another resistor to maintain a load at all times), that would improve things?

Image
Last edited by Bosco on Wed Nov 16, 2016 8:36 pm, edited 1 time in total.
pser1
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Re: Japanese Arcade Joystick Adapter

Post by pser1 »

I think it should not damage anything.
The +5V comes to the joysticks through a 100 ohm resistor
This means that max 5V/0.1k = 50mA would be drained
And power comsumption would be 100*0,05^2 = 0.25 so a simple 1/4W resistor should do
and this is the kind of resistor mounted in a D32-D64

cheers
pere
sorchard
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Re: Japanese Arcade Joystick Adapter

Post by sorchard »

Bosco wrote:if the circuit shorted out, how much current could it draw?
The 5V supply to the joystick ports is via a 100R resistor, which limits the short circuit current to 50mA so nothing much to worry about.

If shorted indefinitely then that resistor would get hot so an industrial belt and braces approach would be to put another 100R resistor on the board between the incoming 5V supply and the rest of the circuit.

It's a nice simple circuit and should work fine. If you're unlucky there's a small chance it will misbehave after a few months of use because the switches are not seeing enough current to break through the oxide that builds up on the contacts. If that does happen then deliberately shorting a pair of switches might clean them enough to start working again. Reducing the 100K resistors to much lower values might help prevent this from happening, but then the voltage drop across the 100R resistor will be enough to prevent a full scale reading making it a bit of a compromise.
Stew
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Bosco
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Re: Japanese Arcade Joystick Adapter

Post by Bosco »

Thanks Stew, Pere.

I feel a lot more reassured and would hate to fry my poor Dragon. :)
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Bosco
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Re: Japanese Arcade Joystick Adapter

Post by Bosco »

Btw. Is there a better way to solder DIN connectors? The pins become wonky if the surrounding plastic heats up making it a very tricky operation.

Can the pins be separated from the plastic disc? They seemed pretty secure.
sorchard
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Re: Japanese Arcade Joystick Adapter

Post by sorchard »

Bosco wrote:The pins become wonky if the surrounding plastic heats up
That's one of those things where the more you do, the better you get, though there are a couple of 'tricks':

One is to use a heat shunt. i.e. clamp something to the pin to remove some heat. Maybe a crocodile clip or long nose pliers & elastic band.

Another thing I sometimes do is plug the connector into a socket to support the pins even if the plastic does soften.

Use new solder if you can. The flux gradually degrades over time and makes for more difficult soldering.
Stew
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Bosco
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Re: Japanese Arcade Joystick Adapter

Post by Bosco »

Great, thanks for the tips Stew. :D
linville
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Re: Japanese Arcade Joystick Adapter

Post by linville »

Food for thought...

http://retrotinker.blogspot.com/2016_06_01_archive.html

The 2nd (and 4th) button parts won't work w/ the Dragon, of course. But that can just be ignored, especially if you are using an Atari joystick with only one button anyway! (Even though the title says "SEGA", it is compatible with Atari joysticks as well.)

Neil Blanchard has these for sale now, but they have the 6-pin DINs the CoCo uses for the joystick ports. I think Neil is working on making some 6-pin -> 5-pin DIN adapters to enable using them with Dragons as well -- you'll have to reach out to him. He is available through neil@cococrew.org and probably some other email addresses as well... :-)

John
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