I'd say the easiest by far would be to open up the steering wheel and find =
the rumble motor. =A0Then use the voltage or PWM going to the motor as an i=
nput to a PIC. =A0A square wave sounds more like a job for the digital outp=
ut to me, then through a divider or whatever to get the right signal level =
to the amp. =A0It sounds like different frequencies generate different rumb=
le levels, so maybe a varying frequency depending on the desired effect.

----------------------------------------
> Date: Mon, 8 Sep 2014 15:49:47 -0400
> From: picdude3@narwani.org
> To: piclist@mit.edu
> Subject: Re: [EE] Force-feedback signal?
>
> 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.
 		 	   		 =20
--=20
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