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We have an Aerovee engine and a Dynon system. We are not getting an RPM reading on the Dynon. Is there anyone out there in the Sonex community that has the same combination that could give us any pointers as to why. Thanks in advance. Rick and Tim. Waiex 0146

Rick and Tim,

The aerovee voltage regulator will only output a signal on one of the two AC input lines. It’s likely you need to switch the rpm pickup to the other AC terminal. As you probably know, the center terminal outputs +12v to the bus/battery, so don’t try using that one!

Jeff

Hi Rick/Tim,
I didn't have a problem with RPM on my Dynon when I was running the AeroVee in my Onex. I don't think it matters which side of the regulator you take your signal from as each side puts out the same number of pulses. I still have your number in my phone from when I sold a prop to you so I'll give you a call after I review my Dynon Installation Manual.

Loren,

The AC lines from the stator coil are interchangeable, but the regulator itself will only output a signal from one of the terminals. See page 47 of the AeroVee installation manual for more details.

Jeff

Hi Jeff,
All I know is that mine worked on both sides with an accuracy of 1% as measured against my friend's tach that he uses to balance props. I now have a CAMit speed sensor on my 2200 that inputs to the same Dynon pins with the same accuracy. Must be one of those magical electrical things!

All,

Loren and I have continued discussing the RPM signal issue offline, and I wanted to update the group. It's hard to say for sure what might be happening as there are other variables we might not have initially accounted for. First off, the internal design of AeroVee voltage regulators may have changed over the past few years, and secondly some RPM instruments may be better at picking up RPM signals from the AC lines than others. AeroVee regulators I am familiar with from the 2006-2010 timeframe had an internal construction such that one AC-in terminal (e.g. one of the outside terminals, not the center +Volts output terminal) would not output an RPM signal like the other one would. I encountered this problem, as did others. Kerry at the factory used to routinely recommend switching terminals if the RPM was reading zero. However, regulators may have changed, and it's certainly possible that a different gauge (better or more sophisticated gauge?) may pick up the alternator pulses regardless and work.

Loren has experience with his Dynon working on both terminals of the regulator (he tested them both), so there's some evidence that either regulators have changed or his Dynon works fine. In either case, it's a simple fix to try if the RPM isn't reading properly (swap terminals). If swapping doesn't work, then there may be a problem elsewhere (e.g. setting the correct number of pulses).

I'll also mention that many EMS/EFIS systems require a resistor in the rpm-sense line to condition the signal to something that the instrument can read properly. Depending on your instrument, you may or may not need it, and the values are all different among manufactures. I use a 10k ohm resistor in my Skyview to "smooth out the bumps" in the signal at high rpm.

Jeff

Thank you all for your thoughts and input. Next week, we will hopefully try to resolve this issue. Rick And Tim waiex 0146