[Diy_efi] Freq change (was Ignition Pickup)

[bcroe at juno.com]

The circuits at these sites are rather elementary and needn't 
be considered intelectual property.  They might be found on 
a computer board, but a considerable amount of signal 
conditioning would be needed for them to work in an auto 
environment.  

The doubler produces a pulse each time the input signal 
reverses, assuming its a clean digital pulse.  However the 
output pulse is so narrow it would never trigger anything 
like a tach.  An RC network (possibly followed with a 
hysteresis gate like HC14) added in the buffered input to
the output gate can be used to stretch the pulse to a fixed
number of millseconds instead of nanoseconds.  Some 
analog methods could produce a pulse with around 
50% duty cycle over a wide frequency range, instead of 
a fixed pulse width.

If I was halving a frequency, I generally would like the 
output pulse to be the same duty cycle, twice as wide.  
All you need for that is the flip flop.

Bruce Roe

On Fri, 7 Jun 2002 01:50:03 -0700 Perry Harrington 
<pedward at apsoft.com> writes:
> If you're interested:
> 
> Clock doubler circuit:
> 
> http://www.uslink.net/~cybercir/cir15.htm
> 
> Clock divider circuit:
> 
> http://www.ee.washington.edu/circuit_archive/circuits/clockdiv.txt
> 
> --Perry

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