Logitech G29 pedals problem

[Raresch]

Hi,

This will be a longer post, so please have patience and read it all

I have the Logitech G29 wheel and some time ago, around 3 months ago, my true accelerator (you will see why "true" is relevant) started to spike on its own between 10-20%. So, after some research, I understand that there might be dust in the potentiometer so I've tried to open up the pedals and clean the potentiometer.

What could go wrong? ... Well, I've ended up breaking one of the cables (the black one) ... So I've had to carefully disconnect the other ones also, I've changed the position of the true clutch with the true accelerator, changed the spring between the two and now I am using the true clutch input as an accelerator input with the accelerator spring inside the physical pedal.

The problem now? Even if the cables from the true accelerator are disconnected from the potentiometer and fixed apart inside the case so that they wouldn't touch, the input accelerator in-game (AC, ACC, and windows config) is still spiking between 10-20% ... But the cables are not even connected ... So I just don't understand why is this happening? How can the input exits if the cables are not even connected?

Then, in the last week, I've had a case where my new accelerator (the true clutch) was throttling on itself, without any input, so I might get the same problem on the clutch as well. Also, in ACC, sometimes, the accel input is looking it's not fully 100% and is spiking between 98-100% on straights. in AC it's fine ... So I have some questions?

1. What choice do I have to fix this? The issues might not even be the potentiometers, but something else entirely ... but what?
2. I am thinking that the cable itself might be broken. Is there any online market where I could buy a cable that has all the wired for the 3 potentiometers and also the end that fixes to the wheelbase?
3. Should I upgrade to another pedal set? like Thrustmaster T-LCM or Fanatec CLS Elite?
4. Any other suggestions?

Thanks for taking the time to read this.

Kind regards .

 

[Locoblade]

You could try installing DIView to see if you can trim out some of the fluctiations at either end of the scale, that way the game shouldn't see them.

Not sure about more fundamental fixes but if you think its a fault within the cable/wheel rather than the pedal pots then for about £25 you could buy a LeoBodnar USB board then wire the pots up to make the pedals a standalone USB device bypassing the Logitech wheel entirely. This would lose PS4 support though if that's a concern.

 

[GeekyDeaks]

I think you might have posted this on reddit? Try connecting the floating throttle input to ground. It's a long shot, since you had the spiking before the disconnection, but the G29 seems particularly prone to floating inputs. This is actually something that can affect electrical circuits in general, especially if they have a nice long wire connected to them as it starts to behave like an antenna picking up the surrounding noise.

If grounding it sorts out the spiking, then that would suggest it might have been a bad connection in the pot. If it doesn't sort it, then it might mean a bad connection in the cable. If you have a multimeter, you might want to test the resistance and see if it's unusually high for the throttle input.

 

[Neilski]

Yeah, the Logitech pots are notoriously unreliable, but sadly no drop-in spares are on the market.

I've just purchased a 3D-printed adaptor kit + new pots from 3DRap; with any luck I'll be using it on at least one pedal today as a test, because I got tired of endlessly opening the pedals up and cleaning the pots, but that is still a somewhat viable strategy (even if you might now need to repair your cable).

Recently, I have mostly just been squirting contact cleaner into the pots after removing the outer pedal housing, having found that stripping things down completely and dismantling the pots to really clean them didn't buy me much more time before the trouble resumed.

 

[Neilski]

Did you do anything further with your pedals yet @Raresch?

I had much the same issues as you (crappy, worn-out pots) and last week I fitted the 3DRap adaptor kit and the new (more standardised) pots that came with the kit.

Outcome: I'm very happy. (So far!)
The plastic gears are a wee bit "lumpy" to look at, and indeed when I first pushed the pedals down by hand, I could feel a slight mechanical lumpiness within the travel. However, I was never able to feel it with my feet, and after a week I can't even really feel it when I push the pedals by hand, so I'm guessing that the high spots on the plastic have worn away.

The only potential downside is that the included pots have a more conventional angular range - something in excess of 300 degrees of rotation I think. The Logitech superspecialcan'tbloodybuyem pots only had a tiny range (70 degrees I believe). Although the 3DRap gearing magnifies the original angular range that arrives at the pot, you still end up with quite a bit less resistance change from the pedal travel. End result: less voltage swing and less resolution.
I wasn't certain that the G27 had an 8-bit ADC on board. To investigate, I captured the packets from the USB interface and this immediately showed me that the controller was only supplying one byte per pedal and also that it was remapping the measurements into the available 8-bit range. (In other words, after a disconnect, if you only push the pedal half-way down, that becomes the new 0 point, while the released pedal will always give a 255 reading.)
I was rather hoping that the raw measurement might be 10 bits (or more), which would make sense given that it's to be remapped into 8 bits... To test this, I dumped a lot of packets while pressing and releasing all three pedals. Sadly, the results suggest that not only is it an 8-bit ADC, it's not even configured very well, because the number of distinct codes I got was actually less than I expected, given the voltage swings I had measured before sealing the pedals up.
Instead of the hoped-for 256 distinct levels from each pedal, I got 79 for the brake, 100 for the accelerator and 104 for the clutch (ahh, the irony of having the most resolution where it matters least!). The measured voltage swings weren't the same for the pedals either (matching the number of distinct codes), but the cause wasn't obvious.
So: I basically have around 6 and a half bits of pedal resolution now, and this is plenty good enough for me!

I didn't measure what the original Logitech pots provided at the digital level, but the voltage swing I measured before removing them was only about 70% bigger than the current swing for my modified clutch pedal - this implies that even the vanilla pots only generated around 173 distinct digital codes, which seems a bit lame (why the heck not configure it to use the full 8-bit range properly??) but heck, it's not like I would honestly expect to be able to tell the difference unless I got down to around 30 steps or fewer.

tl;dr: I can recommend the 3DRap mod

 

[GeekyDeaks]

Hi @Neilski - what measurements did you take prior to swapping the pots? I also noticed the resolution issue on my G29 and I suspect it's simply because the ADC in the wheel works across the whole supply range. With the G29 the range used on the brake was a measly 1.1v from a supply of 3.3v at the wheel. At the pot middle tab, I measured 3.0v at 0 brake, and around 1.9v at full brake with the stock setup.

I did try to see what changing the voltage range would do, so I hooked up another pot to the loom, but even after several attempts at resetting the wheel and providing different ranges, I couldn't get it to accept anything below around 1.7v, which is a range of about 1.3v, so still less than half the likely reference in the ADC

I'm considering bypassing the wheel, since I no longer use the wheel on the PS4 and the G29 also adds a slight curve to offset the rubber block:

This doesn't really work for me since I have replaced the pot with a loadcell. There is a leo bodnar board that @Locoblade has had good success with, and I have also found some example code to allow an Arduino to emulate a joystick/gamepad that I am probably going to use as I have a few spare knocking around https://github.com/n-e-y-s/G27_Pedals_and_Shifter

 

[Neilski]

I also noticed the resolution issue on my G29 and I suspect it's simply because the ADC in the wheel works across the whole supply range.

Freaky. I could have sworn I read somewhere that the G29 used a 10-bit ADC but maybe that was wrong.

the range used on the brake was a measly 1.1v from a supply of 3.3v at the wheel

Yikes, pretty small indeed!

the G29 also adds a slight curve to offset the rubber block

LOL, yes - another discovery I just made recently. I watched a strip-down video of a guy replacing the brake assembly and realised that the G29 has a block in it! (Maybe I read that once in the past but if so I obviously proceeded to totally forget about it.)

I have also found some example code to allow an Arduino to emulate a joystick/gamepad

Yes, I was reading that thread the other day as well - really nice mod! I haven't used any Arduinos yet but they look like fun - might have a go. I was pretty puzzled at the rationale that neys used for the median filtering though: when the pots are that knackered I think replacing them entirely (enter the 3DRap kit) is the only real way out. It doesn't seem unlikely that I'd have had dozens of bad samples in a row with my dying pots, for example.

All in all, I now think there are a whole bunch of good reasons to ditch the Logitech electronics

Anyway, you asked about my measurements. With the supply to the "top" of the pots showing as 4.95 V, I was measuring these voltages (the large variations at top and bottom of the ranges are because the pots were so wrecked):
Accel: 4.3 - 4.6 up, 0.6 - 0.8 fully down (lots of spiking evident even on the multimeter)
Brake: 4.0 - 4.6 up, 0.6 - 0.7 fully down
Clutch: 4.0 - 4.1 up, 0.001 - 0.003 fully down
...i.e. a pretty nice fraction of the total range (basically 4 of the available 5 V).

All three pedals had been completely dismantled in the past, and the clutch gear was last installed one tooth away from the other two pedals, hence the different voltage range. I'm not actually certain which setting was correct though! (The clutch had been working just fine in Windows.)