Potentiometers...

[jkl]

Hi,
I successfully modded my Dreamcast MC2 Wheel to work with Naomi and Lindbergh.
But I wonder "why" it works, since I knew that arcade driving pots are often 5k pots instead of 10k pots I'm currently using..!

Am I putting my jvs I/O at risk maybe?

JKL

 

[nem]

Sega wires pots as voltage dividers. One end of the pot is +5V, the other GND, the wiper is adjusted current. So regardless of if it's a 5K pot or a 10K pot, the voltage will always be 0-5V. It will affect load on the PSU, but most likely a negligible amount.

 

[obcd]

The current will be lower with a 10K potmeter.
The JVS analog inputs also have an impedance.
Due to that, the wheel might have minor different characteristics with a 10K potmeter.
You won't damage your JVS by using a 10K instead of the normal 5K
The 5K forms a 1mA load on the 5V which is neglictable. The 10K only forms a 0.5mA load.
It might be a bit more sensitive to environment noise. If the steering readings are stable, you have nothing to worry about.

 

[jkl]

Many thanks.
Do you know maybe of other wheel sets pot based and easy to mod other than MC2?

 

[twistedsymphony]

Most driving wheels are pot based, chances are if it has hard stops (eg: you can't spin it one direction indefinitely) then it uses a pot.

modding a driving wheel to hook up for analog controls is easy, the hard part is getting the FFB working.

 

[jkl]

Ok.
I thought that modern wheels for pc / console use optical encoders instead.

Thanks a lot.

 

[twistedsymphony]

I thought that modern wheels for pc / console use optical encoders instead.

I can't say for sure (as I haven't opened and examined a good many of racing wheels) generally anything that is less than 360 degrees lock to lock will use a pot. most racing wheels have about a 270 degree range because they're limited by a pot.

There are some fancy 600 and 900 degree wheels that might use an encoder instead, though it's also possible they use gear reduction to keep it in the pot's range. those are the one's I'd be weary about, but those are also the ones that will be hella expensive, AND offer a poor arcade experience since they're designed for SIM racers that can accommodate that large range.

 

[PaulWoodpross3r]

Bump, but since I randomly stumbled upon this thread a while back, I'd like to contribute a few stories about my discoveries with pots and racing wheels:

I recently found this Thrustmaster Ferrari Challenge 2 wheel for Nintendo Gamecube. Took it apart, and was able to rewire the buttons and the main steering pot to the Model 3 (the motherboard is a double-sided PCB so you need to cut traces and follow the tracks), but I additionally discovered that the wheel's hand pedals operate off these slider pots which I believe are used for stereo mixers:
Unfortunately, I had issues connecting the pots. Initially I connected them wrong assuming the top and bottom wire on the harness (left of the middle picture below) were +5V and GND. Come to find out I had the gas signal to +5V and the +5V signal to ground (YIKES!!) or vice versa. Looking more closely at the symbols on the wires, I found the bottom two wires were the VCC/ground connections. Then right after I connected both my gas and brake pots to the Model 3, both gas and brakes were being activated in test mode when I held down the accelerator, but the brake still gave only its one signal. Is it possible I shorted something by mistake?? I've tried cutting the trace to the brake signal on the PCB in the left picture, and it gave same instance via the Ultimarc A-PAC (I had this wheel wired to a DB15 connector with my own schematic and adapters).

 

[nem]

You might have burned the carbon track inside the pot if you shorted it.

 

[PaulWoodpross3r]

You might have burned the carbon track inside the pot if you shorted i

Yeah, there was some burnt plasticky smell inside the wheel after a while. I bought another one to test, but it's really an easier mod compared to the rest of the wheels I've cracked. I had a similar incident with a pot in a Thrustmaster NASCAR Charger (old PC gameport) catch fire while I had tried manually calibrating it for Daytona 2, WHILE the board was powered on. I highly suggest shutting the board off while working with pots or it will cause sparks or burns. It was quite scary to see.
Before I have the wheel all finished, I usually test my buttons or pots with alligator clip-Dupont wires to the filter board. Super useful but make sure no metals or copper touches.

Edit: I bought another copy of the same wheel and it gave the same problem. So on this wheel, you will need to get creative and remove the Lever Board shown in the picture above to rewire the pots and possibly cut traces, but allow me to give one bit of advice -- DO NOT EVER remove the gas and brake paddle shifters! They are an absolute bastard to put back in properly!! Just jiggle the gear and push both dials back with a screwdriver or w/e and pull both of them cleanly.

In short I finished the wheel up, but I had to reuse parts from other Thrustmasters to get it working right. I actually took the Lever Board off of an Xbox NASCAR Pro Victory wheel since I had it slap the hell apart and couldn't figure out how to wire the buttons because they seem to be wired in a way that makes them unsuitable on arcade systems. An expensively crude mod but hey, it works. Had a spare wheel attachment from a PS2 NASCAR Compact wheel to put it back together as I had a hard time with it, also. I put the motherboard from the Gamecube one that was already wired in the PS2 version's wheel attachment, as it fits perfectly.