Controller pot values.

[kensu]

I know at least one person had asked about this in the past, so I'm posting this here.

I just hooked one of my 5200 controllers up to my multimeter (if you don't know, there are needle-like probes you can insert into the sockets of the plug) and determined the range of the horizontal pot to be from 500Kohms to around 190Kohms. Which fits in with Kenneth Simon's schematic that's been floating around that says the controllers uses 640K pots.

 

Hopefully this will be of use to someone (perhaps we could add it to the FAQ?)

[Ataritard]

I have a hand full of loose pots from projects I've done and most of them max out at 504K meaning they are 500K pots. I do have a couple that go all the way to 1350K and 1375K which I found surprising.

[SignGuy81]

I know at least one person had asked about this in the past, so I'm posting this here.

I just hooked one of my 5200 controllers up to my multimeter (if you don't know, there are needle-like probes you can insert into the sockets of the plug) and determined the range of the horizontal pot to be from 500Kohms to around 190Kohms. Which fits in with Kenneth Simon's schematic that's been floating around that says the controllers uses 640K pots.

 

Hopefully this will be of use to someone (perhaps we could add it to the FAQ?)

 

This was in fact very useful, since I was trying to go by this

 

 

Potentiometer inputs are 0-500kohm, linear. Directional inputs are read by a RC delay circuit, i.e. the time it takes a capacitor to recharge after being discharged determines the potentiometer positions.

• North=0 ohm between pins 9 and 11
• South=500 ohms between pins 9 and 11
• West=0 ohm between pins 9 and 10
• East=500 ohms between pins 9 and 10

 

From http://old.pinouts.ru/Inputs/JoystickAtari5200_pinout.shtml which is clearly wrong. I got about the same reading you did when testing, and thought something was wrong, so thank you for posting this.

[7800fan]

If you take apart the 5200 controller and checked, you would see the pot can rotate much further than what the stick allowed. I believe the stock pots are 1Mohm and that only half are actually used for the controller.

 

I have looked to replace the icky non centering analog with modern thumbstick but those generally are only 10k or 100k and I have not been able to find a 500k pot that are of correct size to work as drop in replacement for thumbsticks.

 

Since the 5200 uses R/C delay to estimate position, wouldn't dropping in a cap inline work? I think similar trick was used to make PC controller work on Apple II?

[SignGuy81]

Yes, I knew the pots didn't use the full range I just didn't know where it should start or end. I believe that the page I was looking at was just assuming thinking the pot range was 0 to 500k ohms(wrong on that it is a 500k ohm pot as well) that the input range would be the same on the atari, and then on top of that listed the range as 0 to 500 ohms instead of 0 to 500 k ohms, which either case would be wrong anyway.

Edited December 10, 2017 by SignGuy81

[CMR]

I've been thinking of cobbling together an analog stick controller too. I was going to use the formula found in this article to sort out the cap values, but looking at the 5200 schematic it seems the horizontal and vertical controls use different cap values for timing. Do you think this would be because 5200 pixels aren't square?

 

https://hackaday.com/2012/01/26/analog-joypad-for-your-retro-pc/

[bohoki]

i once did a trigger value test where i put in multiple games moved the stick until the dude moved turned off the machine and measured the value if i recall most games registered a right and down movement at between 350k and 430k and a left and up around 100k but each machine has its own calibration so it can vary but its generally close

 

good thing about the 5200 the controller parts are simple and you wont hurt anything experimenting carefully you can buy a bag or 100 104 capacitors on the ebay for like $1 and just keep putting another in parallel till you are centered buy a bag of 103s to fine tune too

Edited January 6, 2018 by bohoki

[john_q_atari]

Here are measurements I took today on one of my controllers:

 

Vertical Pot

 

1st col: position

2nd col: first measurement

3rd col: second measurement

 

North 1.16K 4.7K
1/2 North 156K 147K
Center 250.4K 274K
1/2 South 367K 340K
South 464.5K 429K
NE 48.9K 80K
1/2 NE 184K 185K
1/2 SW 360K 329K
SW 458K 405K
NW 43K 59K
1/2 NW 145K 148K
1/2 SE 335K 320K
SE 434K 390K

Horizontal Pot

 

West 1.4K 1.3K
1/2 West 145K 121K
Center 250.4K 226K
1/2 East 308K 305K
East 368K 382K
NE 373K 365K
0.5NE 307K 313K
0.5SW 185K 168K
SW 39K 71.5K
NW 47K 47K
0.5NW 145K 151K
0.5SE 301K 313K
SE 360K 358K

Notes:
single unrefurbished stock 5200 joystick with Japanese pots measured
perspective is looking down at joystick from above, keypad at bottom
estimated location of center, diagonal, and half diagonal positions
2 measurements taken at each position (1st and 2nd columns respectively)