Racing Sim Brake Pedal Load Cell Interface
Intro: Racing Sim Brake Pedal Load Cell Interface
A little while ago I undertook the process of scratch building my own PC racing sim. It's all done now but one thing that i'd like to share with you all is how i accomplished a load sensitive brake pedal.
See, in a real car, the pedal does not really move all that much, even less in a race car. The braking force is then proportional to the force applied to the pedal and not the MOVEMENT. The problem lies in that most commercial pedal/wheel setups simply use a spring under the pedal and it detects movement of the pedal, but it just doesn't feel real.
Now, i don't claim to be the pioneer of this load cell idea but i would like to share the interface that i have made to enable one to be used. There is at least one commercial LC interface available by itself or built into a USB joystick board but it seems they have effectively stopped selling them. Hence, they are effectively unobtainable.
STEP 1: How It Works
What this interface does is multiply the output voltage of the cell to produce a 0-5v scale which then becomes useful to ether replace a 'pot' on a commercial pedal set or interface with the likes of an mjoy USB Joystick interface (That's a DIY Atmel AVR based USB joystick interface with 24 buttons and 6 axes).
The amplification is done with the help of a INA122PA from Texas instruments. It is pretty much purpose built for this task. All you need is a 0.22uf filtering cap and a resistor sets the gain.
STEP 2: Construction
All you need to do is source yourself the INA122 chip from your fav electronics outlet - RS, Farnell, Mouser etc. It should set you back less than $10 even in a single item purchase.
Print, transfer, etch and drill the board. I used screw terminals on mine but they can be just soldered directly to the board.
The board layout is attached in Swift PCB format. A free viewer/printer is available for download from them.
Solder the chip and 0.22uf cap in place and select your resistor for the gain. Theoretically, a gain of about 500 is perfect so accoring to the datasheet it needs a 400R resistor. This means we get very close to 5v output when the LC puts out 2 milivolts.
Providing your existing pot is running at 5v, you can simply substitute the three wires on the pot with the 3 wires on the LC interface (negative, +5v and signal) and you then have yourself the beginings of a load sensetive brake.
STEP 3: Wrapping Up
This is a pic of my brake pedal/LC setup.
Enjoy!
26 Comments
phanphamvietlong 1 year ago
AussieMakerGeek 1 year ago
See image...
phanphamvietlong 1 year ago
Binleo 1 year ago
AussieMakerGeek 1 year ago
phanphamvietlong 1 year ago
bebop47 3 years ago
Im using a different capacitor which is 100nf. Do i need a different cap? Im using also a 1k ohm trimmer for adjusting gain. Any thoughts?
AussieMakerGeek 3 years ago
bebop47 3 years ago
funny thing is when i connect the board the voltages on the wires on the pedals goes down to 1.9v
AussieMakerGeek 3 years ago
bebop47 3 years ago
AussieMakerGeek 3 years ago
bebop47 3 years ago
AussieMakerGeek 3 years ago
danielromero963 3 years ago
jeffkruger 3 years ago
AussieMakerGeek 3 years ago
Edit: Or did you mean -5v? The answer to that is you don't, it's just +5v and Gnd which most pedals already have. It will also work with 3v pedals such as Thrustmaster but you might need some more gain
marcinpolniak 4 years ago
MattJ5 9 years ago
Okay I know this is an old post but maybe you can help. I made this and wired it to my tx racing wheel's stock 2 pedal setup. Does not work but when i press the accelerator pedal the brake presses. I can follow most instructions but do not have great knowledge of electronics. The positive wire from the base comes down to the positive or the accelerator pot and then is wired in series to the brake pot. The signal is from the bast to the brake pot and then the brake pot has to wires from the base and the ground in series from the accelerator pot. I just wired it to my board in the same fashion. Any ideas as to what is making this happen?
ClaudemirC 4 years ago