digifiz thoughts

[flaatr@yahoo.com (Euroroc II)]

I'm an RF engineer... Analog comes second nature to me so I didn't even 
think about the digital solution  :-)

Yeah this could be done too... you may need to put an amp of some kind on 
the output of the PIC to generate the same level signal back to the Digifiz 
but the math conversion can be done in Bits as well as Volts.

-Raffi

At 12:08 AM 3/14/2003 +0000, Geoff Hicks wrote:
>I agree the change should be a simple conversion, 8kph is 5mph, a PIC or
>similar device in series with the sender should be capable of doing it. As I
>now have Dirk's GT2 with
>a digifiz display and the UK needs and mph display I will be working on it.
>If anyone has any other ideas I would welcome them.
>
>Note however that the change would mean that the total distance traveled
>would be kilometers up to the change and miles after. Confuse any records
>and insurance people definitely.
>
>I will of course post the results of my work, if and when I have the time to
>do it, on Scirocco list e-mail group.
>
>Geoff in UK
>3 GT2's
>A white 8V for my wife Heather
>A red 8V for me
>And a green 16V to share (with digifiz).
>
>----- Original Message -----
>From: "Euroroc II" <flaatr@yahoo.com>
>To: "Calimus" <calimus@techography.net>
>Cc: <scirocco-l@scirocco.org>
>Sent: Thursday, March 13, 2003 11:26 PM
>Subject: Re: digifiz thoughts
>
>
> > It can be done... the speed sensor that bolts up to the tranny produces a
> > pulse train whose rate corresponds to the speed of the vehicle. The
>Digifiz
> > receives those pulses and counts them vs. time to determine the speed in
> > KM/Hr. Since speed in KM and Miles is a simple ratio and zero is zero the
> > simplest way to do this is to build a small box that receives the pulses
> > from the speed sensor, processes them and outputs pulses at a different
> > rate, a rate that corresponds to MPH.
> >
> > Not putting a lot of thought in it I come up with this idea if speed is
> > determined by pulse frequency. It a two part conversion. First take the
> > input signal and ignoring the pulse width do a frequency to voltage
> > conversion. now take that voltage thru an amplifier with variable gain and
> > run the converted voltage into a voltage to frequency converter. You may
> > need to use a PWM here instead but I don't know since I have never seen
>the
> > signals... I'm only guessing. Adjusting the gain and possibly the offset
> > you should be able to calibrate the display to show MPH.
> >
> > Now if the Digifiz measures pulse widths for speed, which I seriously
>doubt
> > but is possible, you could do the same thing but you would have to do a PW
> > to voltage conversion and defiantly use a PWM at the output.
> >
> > It really isn't as hard as I made it sound... you are talking about 3 IC
> > and a handful of resistors and a potentiometer. All of the parts can be
> > purchased thru Jamaco or Digikey or any other on-line electronics parts
>house.
> >
> > I'll add this to my list of projects...
> >
> > -Raffi
> >
> > At 05:07 PM 3/13/2003 -0500, you wrote:
> > >In the last year that I've been on the list, I've noticed that we have
> > >some very skilled people assembled here.  One of the things thaty throws
> > >me on the digifiz is that it's that the odometer and speedo are in KM.
> > >Do we have anyone on the list that could re-program the eprom (if it
> > >uses one) or make some circuit adjustments so that it reads in american
> > >measurments for some of us dumb folks that hate doing concersions on the
> > >fly while looking in the rear mirror to see if that cop is going to come
> > >after us or not?
> > >
> > >I'fve often thought about doing the digifiz conversion, I love the way
> > >it looks, but so far, cost and the metric system have kept me at bay.
> > >
> > >So what do we have, anyone that knows enough about it to where they
> > >could change it?  Or anyone that if they could look at one long enough
> > >that might be able to make the adjustments?
> > >
> > >
> > >Just thought I'd ask,
> > >William
> > >--
> > >http://www.techography.com/scirocco (s.org forums)
> > >http://www.techography.net:82/scirocco  (my rocco's site)
> > >
> > >88' Scirocco 16v (Crabby 16v)
> > >89' Cabriolet 8v (pretty bunneh)
> > >71' Karmann Ghia (air sucker)
> > >
> > >
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> >
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