Question Help to diagnose 2DOF crash.

I am running my self built 2DOF rig, the SMC3 w/softstart, using simtools 2.4, and arduino UNO, a sabertooth 2X32, and 2 gearboxes.

After running about 6-8 minutes, i start to either get some strange twitching that repeats in a steady pattern, or the motors swing wildly to opposing axis limits (at which point the motors shut off). I have to shut down the motors using my stop button, and if i just restart it just picks up with the same twitching pattern even if i have exited the racing sim, restarted the computer, or anything else. I have to exit game engine and game manager and start the SMC3 program, which then restores the unit to proper working condition as soon as it loads.

This is running the iracing plugin, I currently have no other sims to test with, but I will try LFS tonight.

The question is, what component should I be looking at as causing the fault? My first guess is USB interference to the UNO so I bought some ferrite to try to help with that, it will be here tomorrow. My best guess is it has something to do with the Arduino?

Does anyone have any suggestion how to go about diagnosing the issue?

I have checked that, the hall sensors are functioning normally, and the SMCutil shows no distortion in their signal throughout their range. The twitching affects both motors.......its like the arduino is stuck in a loop. It runs so nice, but only for so long.

Here is what else I have tried:
Replaced USB cord with one with a ferrite on it. No change.
Replaced Arduino UNO with a MEGA. No change.
Restored the 2X32 Sabertooth to default, and reset baud and timeout only. Seems like it got worse.
Tried the sim in LFS instead of iracing. Same problem occurs always somewhere on the 5th lap.

Going to try today replacing the sabertooth with one I had as a spare. If that doesnt work, I have new resistors coming and I'll try ditching the diode/bridge rectifier.

I have attached some pictures of my electrical setup if anyone cares to look. Wiring is a mess because I was changing arduinos and checking wiring.

I am starting to think there is a problem with my bridge rectifier/resistor combination. The resistors stay ice cold, the rectifier gets medium warm.

Maybe I should move this thread to another section as I am realizing this more than likely has nothing to do with game engine, or game manager.

I guess that it could be an overload, but the rig is very well balanced. With someone on it and the actuators disconnected, I can move it up and down with very little force (with me on it and no power applied i can balance it at the midpoint with no effort, if i get off it tilts forward). I am having trouble figuring out how to check if the sabertooth or motors are overloading, the motors either twitch, or rotate so that one actuator is at the up limit and the other is at the down limit. If I use SMC3 and the describe software to monitor the motor amps and volts, and the tracking of the pots to signal everything looks good, but in that scenario only 1 motor is active at a time. It is just very strange that it needs be be "rebooted" by opening the SMC utility every time after it happens.

I have ruled out USB cable interference, the arduino, the game being used.

I will put in the spare sabertooth tonight. If that fails to fix it I will junk the rectifier, and try new (better) resistors.

I have had rare cases like yours and they have been solved by simply changing the USB cable to another port on the computer, I also had a case where the grounding was missing from the power supply socket.
You could try a battery and thus rule out the power supply.

Thank you, I will first try the spare Sabertooth, then if that doesn't fix it, I will try a battery. If I go this route and it works, what type of charger should be used to top off the battery? I would still use my PSU with the battery while in use. I guess I would also need an new E stop config, as now it is set to kill power to the PSU.

The rectifier and resistor have nothing directly to do with each other. The rectifier gets warm because you are running current thru it so just like a wire it can and will heat up with enough current. The resistors may be cold because you have the voltage clamp value in Describe set on automatic. Try setting it to a value just above your power supply voltage and see if they start warming. If they still don't you may not be generating much back current.

Edit: This didnt fix the issue, but it did get better. In frustration i rewired everything and ditched the rectifier/diode. It is now working 100 percent. I think i may have had a bad connection.

You Sir are my savior. I set the voltage to 14, and just ran 25 or 30 solid minutes of hard racing. Used to be lucky to get 8 to 10. Resistors still run cold, and the rectifier is only luke warm but its working. Thank all of you for all of the help.

Edit to add: I dont know if its really a rectifier, its more of a diode preventing electrical backflow to the PSU. Not much of an electrician, im more of a builder.

@Mike Stuart If you test the battery and it works well, contact me and we continue.

I got it sorted out, pretty sure it was a bad connection from the PSU to the Sabertooth. Thanks for everyones help.

Well, the problem is back. It is completely random sometimes I can go for 30 minutes, somtimes for less than a minute. I have completely redone all wiring. Going to try the battery option and will report back.

Disconnected PSU hooked up to a fully charged battery. Got less than 5 minutes. Im putting it on hold, and going to enjoy some racing. Im lost what to do next. Maybe order an authentic arduino? Both mine are knock offs.

You could also try reducing the packet rate from Simtools some. Maybe your arduino is being overloaded. If that still doesn't do it some people have to run at 115200 baud instead of 500000 from Simtools. To change smc3-sps to 115200 just ground pin 8 and reset.

Ok, I dont want to jinx it because every time I have said it was fixed, it wasnt. But I just raced 2 hours straight by doing the fix BlazinH suggested above. Fingers crossed. I was also able to really boost the KP and maximize the settings in simtools with no ill effect. Beware of the knock off Arduinos's is my lesson here.

"I am running my self built 2DOF rig, the SMC3 w/softstart, using simtools 2.4, and arduino UNO, a sabertooth 2X32, and 2 gearboxes.

After running about 6-8 minutes, i start to either get some strange twitching that repeats in a steady pattern, or the motors swing wildly to opposing axis limits"


I have an identical rig to yours Mike pretty much.

I hadn't used mine since relocating it in January - .......long story and a new HDD and new OS later (win 7 to win 10).............what a battle that was in itself.

So I get mine back up and running, amazed at how much I had forgotten already...and just how complicated putting all this together can be - fragmented posts etc.

Mine has a twitch - and now and then would do as Mike said, totally spazz out and motors swing to opposing axis and wobble about about violently until I re-start the arduino by literally unplugging the usb cable.

This in turn kills game engine - restart all, back to normal until the next time, seconds to minutes later........wtf This is almost always in VR so catching faults can be tricky, especially when your rig is having a fit literally.

Tried literally everything short of a complete rebuild and battery to rule out PSU.

A week later, and tens of hours of failure, rewiring, rethinking, find new faults, operator errors, repairing etc etc. I find a major flaw with one potentiometer connection having quite a bit of backlash - quick redesign and a couple 3d prints later - NEW and improved mounts and couplings in PET-G - solid as.

This should just work now, surely, well yes it was way more precise (last fault was a recent development) but the spazzing out behaviour kept returning.

I had read this post a week or so back (thanks Mike for having the same fault) and thought I better check back on this, he said it was fixed last I read.

BlazinH you sir, are a legend!

The flips outs were caused by the baud rate of 500000 being to high for my clone arduino's.....set to the lower rate 115200 and the rig hasn't flipped out once. Have about a 90 minutes so far and would normally have had to reset 10-15 times regardless tune attempts.

I hope this helps anyone else (or me in the future as so of my older posts have recently) with the same setup as Mike and I have.



For what it may be worth - I don't recall having the twitch and random flip outs when my rig was last setup.

Old pc was previous version of simtools(what ever was current Nov-Dec 2018) running win 7 64 bit
Current set is Windows 10 64bit Simtools 2.4.

No settings/files etc were copied from old install. Except the same arduino sketch as previous - BlazinH softstart with Sabertooth etc etc

Cheers Rob

I can confirm its the packet rate setting. The fix suggested above by BlazinH worked 100 percent. I did a 4 hour iracing stint this morning, and its flawless. Stangely, I too was coming off of a fresh reinstall of windows 10.

All of my issues appear to be resolved also, 4-5 hours with no resets