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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.
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Signing UpStep 1How 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.
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The mjoy sounds useful but I can't find much information about it, can you tell me anything more? I obtained a steering wheel/pedal set a while ago, but though it's nicely built (Momo pedals and a solid wooden case) it uses potentiometers and the gameport interface so has terrible precision and drift. I contemplated rewiring it, perhaps with some optical encoders from old mice, and hooking it up to my Arduino, but didn't know how to make that act as a game controller to the PC.
I had a few bits lying around so i thought i'd give it a shot. I started with the wheel and using optical sensors but I just could not get it reliable. It would lose it's center and just generally sucked. You're much better off using pots.
The Mjoy interface was originally developed by a guy named Mindaugus. Unfortunately he has gone missing from the net but his legacy remains in the likes of http://web.archive.org/web/20070228151145/www.mindaugas.com/projects/MJoy/
I used a board based on the one found here translate.google.com.au/translate (Click on the PCB link). I made some minor changes to it to increase some track gaps and added the ability to use normal diodes for the buttons rather than SMD. I have got heaps of pics of my sim build as well as the mjoy board stuff on my site - http:///www.hux.net.au