Yes,  It was me with the rocker arm idea, and with the pulse on the injector
line.
I was a heavy equipment mechanic for a long time,  and the timing light we
had
used an inline pressure switch that activated the light.  I didn't like it
much
as we always had to have all kinds of adapters and such.  I normally just
set the engine crank where I wanted it,  then pressured up the pump and
rolled it
to point of injection, then tightened the pump coupling.  But any rate, back
to your
topic, the switch was sprung for Right below injection pressure,  It had a
very small
pin in a very small block, an adjustable spring (to control trigger pressure)
 and a microswitch.
The pressure has to be very small so you don't take too much displacment from
the line, there
as affecting the timing.  We adjusted the spring until we had no reading,
then backed it off
just to where it would flash.  This would be right below injector pressure.
It worked great, especially
if we would have had only 1 engine to use it on.  But with anything from a
Komatsu to a Cummins or
Cat,  every line/fitting was different!

I heard of just a clamp on sensor that clamps to the outside of the line and
registered pulses, but
did not ever use one.  The spring loaded block would be real easy to make, if
you have access to
the tools.

Yes the alternator idea does work, but I have had bad experiences with it.
Belt slip,  alternator loosing
a diode and so on,  but, It makes one hell of a charging circuit warning
indicator,  in a boat, thats
manditory !!!!  <grin>



Richard Skinner
rwskinner@worldnet.att.net

----------
> From: Wim E. van Bemmel <bemspan@XS4ALL.NL>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: pic tachometer...for Diesel engine..
> Date: Thursday, January 15, 1998 4:00 PM
>
> Hello,
>
> thanks .. I asked EXPERIENCE, no ideas untested ideas.
>
> Sorry about beiing a little rude about this, but I think that if you dont
make
> your statement very clear you invoke a thread that leads to wonderful
> discussions.. Goats.. Lawnmovers (sic) the "v" is meant as that.. Sometimes
I
> love them, and participate as well, but not if I have a serious thing to
solve.
> White lines do NOT stay white, and paint peels off in a seaborne
environment.
> Better is my idea of using Scotch or 3M reflective tape and use Infrared
devices
> through an infrared filter..  needs some cleaning now and then though.
> Thank you all for the experiences you shared! They are useful, I'll try
first to
> get the RPM info from the alternator, and second best is the attack through
the
> valve rocker cover, I think. That way there are no crucial parts in
dangerous
> areas.
> There was a response to my idea of using the injection pipe jerk.. did not
fully
> understand that answer.
> For a quick hookup the approach of using the flywheel rim by inserting a
magnet
> or putting on a reflector seems to be the best. It gives a direct RPM info,
no
> calculations in the PIC to correct for the pulley diameters..
> Thanks again, let us go to the original question, how to implement that in
PIC.
>
> XYGAX wrote:
>
> > Paint a white line on the flywheele and use one of those reflective opto
> > switches then count pulses it also has the advantage of being a non
contact /
> > no mechanics interface
> >
> > Cheers Steve.....