Tutorial DIY Load cell brake on Thrustmaster 2 pedal set (NO ARDUINO)

Hi there,

following steps from other thread of this forum ( https://www.xsimulator.net/community/threads/ina122-for-thrustmaster-tx.14653/ ) I converted my crappy 2 pedal set brake from cheap Thrustmaster wheels in something slightly better, which allows me to modulate the braking very well. I have almost everything documented, therefore I leave it here.

The premises when making this mod were:

• Spend as less as possible
• Do it on 2 pedal set and not on T3PA or similar for a matter of lightness (they will be linked to a Playseat Challenge that I carry up the stairs, down the stairs every time I use it)
• To be "transparent" for the PC, console, or whatever is going to be used with the steering wheel, that is, it is still plugged in with the normal connector on the steering wheel, no arduinos involved.
• Entertainment and the satisfaction of doing it yourself

Starting point is the typical set from cheaper Thrustmaster wheels

We need a load cell like this one (20Kg is enough)



Electronic components needed:

• INA122P amplifier
• 1 kilo-ohm potentiometer
• 0.1 microfarad capacitor

With these components we have to assemble an electronic board following this diagram:



Cut the cables that go to the brake potentiometer, and solder them to the PCB that we made according to the previous diagram. Also solder the 4 cables that come out from the loadcell to the board. This way, the steering wheel is not aware that the signal that reaches it comes fom the load cell instead of the brake pot.




I made a support with the 3D printer to hold the loadcell, and another for the pedal / loadcell linking, which is based on a squash ball to give some elastic feeling to the brake. I had to use a dremel to open a hole in the pedalboard cover in order to allow the loadcell popping out there.




I also did supports with the 3D to adapt metal pedals to have fancier look



And finally I put two Xbox gamepad motors to add vibration in wheel locks (braking) and throtteling slipping . This is by means of an Arduino board following a tutorial from other forum.

And this is the final look.



I made a couple of videos of the first tests.




On this link you can download the parts made with 3D (cell support and squash ball support):
https://www.thingiverse.com/thing:4819031

The brake now goes very well, it is a relatively simple mod, and I am quite happy with the result.

Best regards.

PS: I added a pair of torsion springs to the accelerator from an old device to give the pedal more stiffness, because it was too soft for me.

Another important detail with the throttle is being sure that the potentiometer gear links with the pedal in the proper place. In the picture below you can see that the first tooth of the pedal engages in the fifth "valley" of the potentiometer gear. This is how I originally had it. That way the accelerator was not working well. The first section of the stroke (about halfway through) did nothing. So I tried different positions, until I found the right one. In my case it is the third "valley". On this position the accelerator works progressively throughout the pedal whole stroke.



PS2: wish thank the members @RacingMat and @Erik Middeldorp . This work has be done thanks to their previous contribution

You are right. Fixed. Thanks

Hi friend, I build the load cell with your tutorial, very nice one!!!
but dont know how to ajust the potentiometer, can you help?

Hi, in my case I put it on the "softest" position, that means, you do not need to push too hard to get max braking (take into account that the load cell sits on 3d printed support, so you do not want to apply too much force on it).


That is done rotating the pot screw clockwise if I remember well.

THX man! I have figure out, clockwise make pedal harder, 240om make me feel best

hi! thanks for the great tutorial first of all. do you know by any chance what will be the wiring pattern for t3pa pedals? searched everywhere but couldnt found a solid info. thanks in advance.

Hi Berk, I do not know how wiring is in t3pa pedals, but taking into account that potentiometers should be the same, just identify which bunch of wires go to each 3 terminals of the pot (signal, ground and +ve) and translate them to the 3 spade terminals of the PCB that goes to the loadcell.

Should be quite straightforward.

Hi, do you have more your pcb pictures? Top and bottom view? Diagram is not clear for me, i am confused with those blue (brackets) in scheme. I assume "brackets" means that i need break(separate) the line? Hard to explain what i do not understand

I tried implementing this mod for my TX 458 pedals but seemed to be unsuccessful. I get no output from pushing on the load cell even after adjusting through the full range of the trim pot. I used a slightly modified wiring diagram with help from another user on thingiverse, but still has the same connections to the INA122P amplifier as far as I can tell. On the original potentiometer cable side, I measured the voltage between the blue signal cable & ground is measuring 2.8 V and the voltage between the red +VE cable & ground is measuring 3.3 V. On the load cell side, the voltage between the red & ground is 3.3 V, the voltage between both white & ground and green & ground are each 1.65 V. I'm not sure what other connections to test as I'm not super well-versed in electronics. Does anyone have any suggestions? Thanks!

Hello,

could it be that you still have to separate the conductor track "C" after your resistance?!

my english is not the best i hope you understand me

Greetings

Track C isn't connected to anything else so I don't think so? I am not sure. The resistance that I am using the set the gain of the amplifier is between E3 and D5. It seemed other people have been having issues with the INA122pA chips from Aliexpress. I ordered 2 chips and both have the same issue with constant output voltage even when there is a voltage differential (~5 mV) between the +/- load cell signal cable. I ordered an AD623ANZ from Mouser USA to see if switching out the amplifier solves the problem and am waiting for that to arrive.

I received the AD623ANZ and it worked flawlessly with the original circuit. The gain calculation is a bit different between the two amplifiers but the 1k ohm trim pot is sufficient for the AD623ANZ.