2600 paddle potentiometer range

[Jess Ragan]

Quick question... does anyone know the value of the potentiometer in the Atari 2600 paddle? I kind of want to adapt it for use with the Xbox 360, but the range for each axis of the 360's analog thumbsticks is 10K Ohms. The resistance value of the Atari 2600 pot has got to be pretty close in order for this to work.

[intvnut]

Quick question... does anyone know the value of the potentiometer in the Atari 2600 paddle? I kind of want to adapt it for use with the Xbox 360, but the range for each axis of the 360's analog thumbsticks is 10K Ohms. The resistance value of the Atari 2600 pot has got to be pretty close in order for this to work.

 

Looks like the Atari pots are 1MΩ if that page is to be believed. To make them work on the Xbox360, you'd need to do more work than just "hook it up."

 

Do you know how the Xbox360 controller senses the potentiometer? If it's looking for a voltage range with a linear transfer characteristic on a high-impedance D/A input, then it shouldn't be too hard to arrange for that. If it's doing something like the capacitive-discharge method common w/ old 8-bitters, then it's maybe a bit more complicated.

Edited December 12, 2008 by intvnut

[potatohead]

They are 1Meg Ohm, linear.

[potatohead]

They are 1Meg Ohm, linear.

 

You could probably put something in parallel with that to cut the range.

[Jess Ragan]

Thanks! I cracked open a paddle controller out of curiosity, and indeed, it's 1 MegaOhm. I suppose I might be able to replace the potentiometer with a 10K model. As for the Xbox 360's method of reading input, I think it's voltage-based. This is what I was told on another forum:

 

"The POTs are 10k, like a 10k Resistor between Voltage and Ground, then the Wiper is the signal line the controller IC 'reads' to know where the stick is at. When the stick isn't touched the Wiper is in the center and the voltage divided evenly (it's not that precise but for illustration sake it is) then when pushed in one direction it's closer the Voltage rail and more voltage is on the signal line, pushed the other way it's closer to Ground and less voltage is on the line. There's 2 POTs per stick also for both axis, an X-axis (left/right) and Y-axis (up/down)."

[Rybags]

Wouldn't it be easier to just wire in a pot and switch (to change between X/new pot) on the XBox controller.

At least then you'd still have easy access to the other buttons.

[BigO]

Thanks! I cracked open a paddle controller out of curiosity, and indeed, it's 1 MegaOhm. I suppose I might be able to replace the potentiometer with a 10K model. As for the Xbox 360's method of reading input, I think it's voltage-based. This is what I was told on another forum:

 

"The POTs are 10k, like a 10k Resistor between Voltage and Ground, then the Wiper is the signal line the controller IC 'reads' to know where the stick is at. When the stick isn't touched the Wiper is in the center and the voltage divided evenly (it's not that precise but for illustration sake it is) then when pushed in one direction it's closer the Voltage rail and more voltage is on the signal line, pushed the other way it's closer to Ground and less voltage is on the line. There's 2 POTs per stick also for both axis, an X-axis (left/right) and Y-axis (up/down)."

 

If one end is connected to ground and the other is connected to a voltage source and the wiper supplies the signal to the console, that would be what is known as voltage divider mode. The Atari paddles aren't implemented in the same way. Voltage divider requires 3 wires connected to the pot, but the 2600 just has two wires to use the pot as a variable resistor which controls the rate of charge of a capacitor which indirectly indicates the wiper position.

 

As has been discussed several times in AA forum pages, the voltage divider configuration is less susceptible to the "jitter" that is common with 2600 paddles.

 

If the 360 does use the voltage divider methodology, the 1 Meg pot might work fine as long as the power supply isn't somehow sensitive to the total current draw through the pot. You'd have to rewire, but if your goal is to control the 360 with what appears to be a 2600 paddle controller, I'd first try rewiring and using the 1M pot to see how it works. (Although, just because I'd try it doesn't mean you won't let the smoke out of your 360 if you try it)

Edited December 12, 2008 by BigO

[Jess Ragan]

Heh, no pressure, right?

 

The weird thing is that there's already a potentiometer on the controller I modified, but it's unlike anything I've seen before. It spins infinitely in either direction like a spinner, but at a constant rate like a paddle. It used to be connected to a plastic disc that turned very reluctantly, scraping away at the top of the joypad with every spin. I love the concept of a modern game controller with a built-in paddle, but MadCatz did it so badly in the Arcade Stick that it's hard to get excited about it. It's great for hacking, though!