Load Cell fluctuation

[shushkata]

Hey all , i am new to the Load Cell World and i want to hear some opinions regarding a "problem" (or not). I just got the BJ Simracing Steel GT pedals, and i started to play with the settings and all. What i see is that when the max force i set to something lower, like 30-40-50%, the readings when the pedal is pressed are fluctuating, like:
55%-57%-56%-55%-58%, they never stop changing.
Throttle is with a Hall sensor, so it's perfectly stable and smooth. The Load Cell is rated at 200kg, is it normal for the readings to have this margin of error ?

 

[Deleted member 197115]

That sounds like grounding issue. Check out this bulletin from HE on similar problem and solution.

 

[Enzo Fazzi]

Fluctuation of a few RAW is quite normal, we're talking anything between 1 and 10 RAW. If the RAW value fluctuates more than that, there is most likely an issue.

Setting the maximum force lower just means that the normal fluctuation has a bigger effect on the calibrated output percentage.

 

[ao1977]

the readings when the pedal is pressed are fluctuating

But how do you ensure you always press with the exact same force and the fluctuation does not come from your foot?

 

[shushkata]

Thanks for the ideas. I also talked to the guys from BJ and they think it's grounding issue. Unfortunately i don't have a grounded electrical installation in my home (old building and all). It's sure hard to press with the same force, but it's present even with small force applied , where you can really control your input. I am trying to find a solution to attach the brake electronics to something grounded ....

 

[blekenbleu]

something grounded

Attaching to the PC chassis is a first approximation.

 

[shushkata]

I have tried using the "Zero" of the electrical socket as my building is old and i hardly think it's properly grounded. So , this was a possible solution, but it's does not make any difference. I will talk with the guys at BJ Simracing tommorow , i am out of ideas really. I don't think that this fluctuation is a big deal when racing, just want to go to the bottom of this

 

[Peppelino]

I have tried using the "Zero" of the electrical socket as my building is old and i hardly think it's properly grounded. So , this was a possible solution, but it's does not make any difference. I will talk with the guys at BJ Simracing tommorow , i am out of ideas really. I don't think that this fluctuation is a big deal when racing, just want to go to the bottom of this

No proper ground in your building?

Here you go : scrape off some paint on your *waterfilled radiator. Connect a cable with a crocodile clip.. Important : No extra ground anywere !! only from cable to wall
outlet.

I think you know what do next...

No change.. hm,.. faulty power supply, injecting jitter and / or hum into that sensitive loadcell curcuit.
Which probably need some additional decoupling, with capacitors.
EMI problems might be cured with that the (suspicious) cables, get twisted around ferrite-cores.

* But I always start with checking cables and connectors.

 

[Deleted member 1066209]

That sounds like grounding issue. Check out this bulletin from HE on similar problem and solution.

Here's a silly question: Do hydraulic pedals suffer from grounding issues too?

[edit]: I would guess that they do, but I figured I'd ask the knowledgeable folks here.

 

[Peppelino]

Here's a silly question: Do hydraulic pedals suffer from grounding issues too?

[edit]: I would guess that they do, but I figured I'd ask the knowledgeable folks here.

Why would they do that ?
Hint : Electronics involved ? Y / N

 

[Enzo Fazzi]

It's not a grounding issue per se anyway, it's electromagnetic interference messing with the USB controller. Grounding all your devices is one way to tackle it, although it is not a bulletproof solution.

 

[Peppelino]

It's not a grounding issue per se anyway, it's electromagnetic interference messing with the USB controller. Grounding all your devices is one way to tackle it, although it is not a bulletproof solution.

Yes. Agreed. You're absolutely right.
There are exceptions to the rule.

Above, commenting shushkata's
Issue with his loadcell, I hinted at just that. The other things, that is important and may fix the unwanted fluctuations. Screening sensitive stuff may also help.
Thank you Enzo.

 

[shushkata]

Do you think something like that can help. It was suggested for the guys of BJ Simracing.

https://www.amazon.com/GeeekPi-Isolator-ADUM3160-Isolation-Protection/dp/B07QKYYCD8/ref=pd_day0fbt_img_1/132-7101224-9155333?pd_rd_w=4QCc1&pf_rd_p=bcb8482a-3db5-4b0b-9f15-b86e24acdb00&pf_rd_r=6BFEYWCAKQJ3B5QZYJXX&pd_rd_r=ab030e93-d298-4822-81c1-66b2135290ec&pd_rd_wg=ndkJN&pd_rd_i=B07QKYYCD8&psc=1

I have dug out an old USB cable with two ferrite elements on it. It helps a bit , minimizing the variation in the signal.

I have further minimized the problem, by changing the power supply cable of my computer. Now the fluctuation is around 1.0 - 1.5% with 45% detection force (of the 200kg load cell)

 

[Peppelino]

Do you think something like that can help. It was suggested for the guys of BJ Simracing.

I have dug out an old USB cable with two ferrite elements on it. It helps a bit , minimizing the variation in the signal.

I have further minimized the problem, by changing the power supply cable of my computer. Now the fluctuation is around 1.0 - 1.5% with 45% detection force (of the 200kg load cell)

Asking me... Yes, looking better now, but spending 21.95 on that usb thing ain't nothing I would recommend.
However using very long cables is
one thinkable source of trouble. Try some more with ferrite-cores then. See what happens.
Remember also, that it's almost allways the end-users fault. they say.