Home-brewing an ignition advance control

[Bruce Plecan]

-----Original Message-----
From: am018 <am018 at post.almac.co.uk>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Wednesday, October 28, 1998 5:26 AM
Subject: Re: Re : Home-brewing an ignition advance control


>Sounds fairly sound --
>My knock sensing idea revolves around using is to take the ouput from a
>knock sensor

Not to be picky, but if it's piezio then it's a vibration sensor, it's
the electronics that tune it for something resembling knock.

>via a pre-amp to a filter then drive an  LM3915 or LM3916 LED driver via
>either the peak detection or power averaging circuits shown in
>datasheets for
>theses ICs. For a knock  indicator it would stop there -- but the  the
>LM3915/6
>LED outputs could be used as comparator outputs and passed to a PIC
>device.   A
>selected high level indicating  knock.  The lowest level should be
>continuously
>"on" when the engine is running and could be used to indicate the knock
>sensor
>is healthy.
>Am I going off the rails or will this work ?
>Andy Mcf
>
If your using a piezio device all your looking for is noise, and it
doesn't care about the source.  A lifter can turn an acoustic
sensor on.  Need to look inside the cyl., like for ionization.
  The reason I mention the above is I spent a bunch of time with
555's, and sent their output to a gm ESC module.  Turns out there
was two frequencies that it was listening for..  When you hooked 
a speaker to the 555 both sounded like pinging.
  Also, in the acrhives is a thread about this, and a chip part no for
an acoustic device, such as what you doing.
Cheers
Bruce