I'll add that I'm using a Logitech G25 force-feedback steering wheel.

Cheers,
-Neil.



On 9/8/2014 2:44 PM, Neil wrote:
> Hi All,
>
> Need some quick assistance for a project I'm taking to the Orlando Maker
> Faire this coming weekend... I'd like to add seat vibration to a race
> car simulator, which is essentially a PC-based race car game, race seat,
> force-feedback steering wheel, pedals and gear-shift, but with real
> gauges instead of the usual on-screen ones.  For the curious, gauge data
> gets dumped out of the game (LFS) to UDP, Python takes that and spits it
> out the serial port, a PIC18F takes the serial data and converts it into
> a digital stream with 6 parameters, and each of the 6 gauges on the dash
> will grab whichever piece of data they need from the bus stream.
>
> This is what I have for the seat vibration...
> http://www.thebuttkicker.com/gamer2 . It's essentially a subwoofer
> that's bolted under the seat, but there's an issue in that it uses line
> level audio for it's input so connected to a speaker output, it rumbles
> more (due to wind, engine and some road noise) as the car goes faster,
> and that's out of sync with what's expected... ie: rumbling/jolting when
> the car goes off-road.  The force-feedback signal that goes to the
> steering wheel has the rumbles/jolts correct.
>
> I've connected the buttkicker input to a function generator and a
> low-frequency (~30 Hz) signal produces a nice rumble... even a square
> wave works well.  But now I need to get the force-feedback signal to
> modify the amplitude of a square-wave signal I generate. There are two
> options I can think of...
> (a) Grab/convert the motor signal (from inside the force-feedback
> steering wheel) and have that modulate the square wave.
> (b) Use acceleration/velocity data from the game (which I can get and
> also dump out the serial port) to modulate the square wave.
>
> Any of you know about these force feedback wheels and can tell me if (a)
> will be relatively simple?  IE: can I just isolate and filter the motor
> signal to get a signal whose amplitude varies with the force that the
> game is applying to the wheel?  That would then go into an op-amp
> voltage-controlled amplifier to drive the butt-kicker.
>
> If I use the data from (b), I can have the same PIC generate an analog
> output (proportional to how much rumble is required) and a separate
> 30-Hz square wave.  Both of those would go into a VCA also as in (a).
>
> I have only a couple days to do this, so any help in figuring out the
> easiest path here or any other options would be appreciated.
>
> Cheers,
> -Neil.
>
>

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