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Dynon tach problems

R

RV10 SS

I'm New Here
110 hours of operation and now my tach is eratic on my EMS D-120. About mid roll on takeoff I get 150-300 rpm jumps. On a static run, the tach is fine until about 2500 rpm. I had the 100K resistor installed. Dynon suggested 150K. Then 180K. With the 180K the tach got eratic at 900 rpm. Sent D-120 to Dynon and now its shipping back with no problems found. I have tried new p-leads and isolating the Dynon tach wires from the switch to the D-sub. All tach readings have been verified with a TruTach.

IO-540 EXP
Slick Start
Slick mags


Thanks!
_______________________
Steve
RV-10 Flying
 
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Join the club! I have the same setup (IO-540, Slick, using the p-lead for tach on a D120). I had the same issue: at lower resistance values, the upper RPM ranges read erratically. When I upped the resistance, the upper range was good, but the sub-1200 RPM range was erratic. I finally got frustrated and installed a 100K pot in series with a 30K resistor (so I can get 30-130K resistance adjustable in flight). I have been unable to find a resistance that works for all RPM ranges. I'm probably going to just settle for having the upper ranges correct and deal with the weirdness near idle.

I posted this earlier: http://www.vansairforce.com/community/showthread.php?t=70840

-Rob
 
Same here, I am never really sure above 2600 RPM what is really happening, but I figure its near enough, the vast majority of the time you are at 2500 or less so the 100K resistor has worked mostly for me.

Seems to be only the IO540 and mags that causes the grief, I have not heard of others having this problem.

I have been tempted to try adding a few Kohms but its too much like hard work :rolleyes:
 
Thanks for responding guys. Dynon has been working with me to fix the problem, but they have treated me as if I'm the only one who still has this problem after using a higher resistance resistor. All of the other threads I have found on this issue appear to have been resolved using a higher resistance resistor. When my unit returns I will continue to work with Dynon to resolve the problem and your comments will be noted.
 
I am not that familiar with the 540's, but can't you just use a transducer like in the 360s? I use with transducer with my 360/Dynon and it is spot on.
 
Jamie said:
I am not that familiar with the 540's, but can't you just use a transducer like in the 360s? I use with transducer with my 360/Dynon and it is spot on.
Click to expand...

Yes, definitely. I may end up doing that in the future, but wanted to save the cost/complexity/weight of the separate transducer if possible.

-Rob
 
Thanks, Rob... I looked at your installation manual, and it looks like you give the sensor +5V excitation. Do you know whether that sensor would work with a 12V input directly off the main buss? The Dynon manual says the output peaks need to be at least 10V.

-Rob
 
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The AFS RPM sensor can run up to 24V, you will need a pull-up resistor between the power and sensor output (red and white wire).

Rob Hickman
Advanced Flight Systems Inc.
 
If by any chance you do end up going with the Vans transducer, it is an eight pulse unit, but runs at half engine speed, so the EFIS is set for a 4 PPR.

Been there, done that.

One point if favor of the transducer------it is independent of the ignition system, so if you change to EI later, it still works.
 
N401RH said:
The AFS RPM sensor can run up to 24V, you will need a pull-up resistor between the power and sensor output (red and white wire).

Rob Hickman
Advanced Flight Systems Inc.
Click to expand...

Rob, curious why you say I'd need a pull-up resistor. The AFS instructions don't show one. Do you do that internally?

Thanks...

-Rob
 
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