More VSS

[T Hergen]

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100 mile | 2000 pul | 1 hr     |  1 min   |    200000 pulses
---------|----------|----------|----------| = ---------------    
 1hr     |   1mi    | 60 min   | 60 sec   |     360 sec
 
    56 pulses    
=   ---------  = 56 Hz
      1 sec
 
 
56Hz is the output from the 2000 pulse per mile sender at 100 MPH.
 
Given that your trying to multiply by two, you need at least 110 Hz.  
Input sampling may not line up exactly as desired either which is
the other reason the frequency needs to be doubled.  I'd probably
use something a little faster.
 
Unless you know what your doing, don't mix 74LSxxx parts and 74HCxxx
parts.  The input thresholds are different.  Stick with one or the other.
If you use a TTL osicillator as was suggested (do they go this low in
frequency?), use the 74LSxxx series of parts.

Tom

On Wed, 30 Sep 1998, Bruce Plecan wrote:

> 
> -----Original Message-----
> From: jdzura at csc.com <jdzura at csc.com>
> To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
> Date: Wednesday, September 30, 1998 2:01 PM
> Subject: Re: More VSS
> 
> 
> >The DS-C304 is a ttl output Crystal oscillator. Nearly any frequency will
> do, but the slower the better. The frequency of the oscillator defines the
> width of the pulse coming out of the Xor gate. At 100 MPH, the VSS freq
> should be 2*100*2000, or 400KHz  right?  As long as the oscillator is 500
> KHz or above you should be OK.
> >I'm pretty sure Digikey has 1 MHz XO43 Style oscillators.
> 
> OK, I been thru the Newark, and Digi-key cats, and the 7474 are
> SN74LS74AN, is that the same part?.
> I can't find a DS-C304A anywhere...
> Is a MC74HC86N the right thing?.
> Bruce
> >
> >Let me know if you have any problems / questions.
> >
> >Joe D
> >
> >
> >
> >
>