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1. 02:56 PM - Re: Low RPM from Plasma II+ and P-lead to Dynon d-180 (Carl Froehlich)
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Subject: | Low RPM from Plasma II+ and P-lead to Dynon d-180 |
Back when I had Lightspeed II+ ignitions I ran into this problem trying to
get the tach output from the ignition to work with the Grand Rapids EIS. It
turns out the Lightspeed Tach pulse is the problem. It is too narrow and
too low of an amplitude to work with many engine monitoring systems.
I tried talking to Klaus to find out what kind of signal the Lightspeed was
putting out. The only response I got was "the units were tested before
shipping and any problems you have are a result of your poor installation"
or words to that effect. The good folks at Grand Rapids however worked with
me to find a solution. By modifying the input to the EIS I was able to get
the Lightspeed Tach signal to work (I had to replace one resistor with a
lower value and remove one capacitor - 10 minutes max).
Recommend a call to Dynon. Tell them the issue and perhaps they can offer a
mod as well.
Carl Froehlich (RV-8A 500 hrs)
RV-10 (fuselage)
From: owner-rv8-list-server@matronics.com
[mailto:owner-rv8-list-server@matronics.com] On Behalf Of Vincent Himsl
Sent: Sunday, July 12, 2009 2:04 AM
Subject: RV8-List: Low RPM from Plasma II+ and P-lead to Dynon d-180
I have the digital pulse information from my Lightspeed plasma II+
electronic ignition feeding one input to my Dynon D-180 and a magneto P-lead
tap through 30 k resistor (per Dynon manual) to the other RPM input of my
Dynon D-180.
Problem is that with the P-lead Pulse per revolution set to 1, and the Plasm
II+ Pulse / rev set to 2, my Dynon reads 2 to 3 hundred rpm low at 900 rpm
(verified by Tru-Tach) and 4 to 6 hundred low at the high end (2100 to 2700
rpm).
I removed the Dynon and using a square wave generator providing 12 volt
pk-pk referenced to ground tested both inputs of the Dynon. It is right on.
I also dropped the voltage down to as little as 8 Volts Pk-Pk and the Dynon
remained accurate.
Suspecting that the Dynon averages both inputs, I tested each input by
removing the other. Both the Plasma II+ and the P-lead were reading low
rpm's compared to a tru-tac (which can be calibrated by aiming it at
flourescent lighting...pretty slick).
By Resetting the pulse rate of the Dynon to 1.5 for the Plasma II+, I get
readings that are consistently 60 rpm low. The P-lead with the recommended
Dynon resistance of 30K reads 2 to 300 low.
My temporary fix at the moment is to remove the P-lead input to the Dynon
from the Magneto (Slick brand via aerosport) and keep the Plasma II+ input
set to 1.5 pulses / rev even though the Lightspeed manual says it should be
2 pulses.
Has anyone else been down this road? If so would appreciate hearing the
solution before I haul a scope to the airport.
Regards,
Vince_Himsl
RV8 N8432 Flying! (10 hours)
_____
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